

/

(x,y)
(x,n)
or x
<<
n
( = x
>>
(n)
)(x,n)
(x,y)
(x)
(x,y)
and min(x,y)
(x)
(x)
({x = []})
({x = []})
(x,y,{flag = 0})
(x,{v = x})
(x,{v = x})
(a,b,c,{D = 0.})
(x,{v = x})
({x = []})
({x = ""},{flag = 0})
({x = []})
(x)
(x,y)
(x,{n = 1})
(x,y)
(x,y)
(x,n)
(x,y)
(x)
(x,{v})
(x,y)
(x)
(x)
(x)
(x)
(x)
(x)
(x)
(x,{v})
(x)
(x)
(x)
(n,k)
(x,p)
(x)
(x,{n})
({N = 2^{31}})
(x)
(x,{&e})
(x)
(x)
(x)
(x,{&e})
(x,p)
(x)
(x)
(x)
(x)
(x,y)
(x)
(x)
(x)
(x)
(x)
(x)
(x)
(x)
(n,x)
(nu,x,{flag = 0})
(x)
(x)
(x)
(x)
(x,{n})
(x)
(x,{flag = 0})
(x)
(x)
(x)
(a,b,x)
(s,x,{y})
(s,x)
(x,{flag = 0})
(x)
(m,x,{flag = 0})
(x)
(x)
(x)
(x)
(x)
(x,n,{&z})
(x)
(x)
(x)
(q,z)
(q,k)
(x,{flag = 0})
(s)
({x = []})
(x,k)
(x,y)
(x,y)
(x)
(x,y)
(x,y)
(x)
(x,{b},{lmax})
(x)
(n,{flag = 0})
(n,{flag})
(x,y)
(p = a,b,expr,{c})
(x,y)
(x)
(x)
(x,{lim = 1})
(f,{nf})
(x,p)
(x,p,a)
(x)
or x!
(n,{flag = 0})
(x,p,{flag = 0})
(x)
(p,n,{v = x})
(x,y,{flag = 0})
(x,y,{p})
(x)
(x,{flag = 0})
(x)
(x,{&n})
(x)
(x,y)
(x,y)
(x)
(x)
(x)
(x)
(x)
(x)
(x)
(x,{flag = 0})
(x,y)
(x)
(x,y,l)
(x,n)
(x,n)
(x,p)
(x,{flag = 0},{D},{isqrtD},{sqrtD})
(D,{flag = 0},{tech = []})
(x)
(D,{flag = 0})
(x)
(D,{v = x})
(D,f,{flag = 0})
(x)
(x)
({x = []})
(x,{k = 1})
(x)
(x,g)
(x)
(x)
(n)
(E,z1,z2)
(E,n)
(E,n)
(E,p,{flag = 0})
(E,z1,z2)
(E,v)
(x,v)
(E,k,{flag = 0})
(om)
(E)
(E,z,{flag = 0})
(E,x)
(E,{flag = 0})
(E,z)
(x)
(E,p)
(E,s,{A = 1})
(E,z)
(E,x)
(E,z)
(E,z,n)
(E,{p = 1})
(E,z,{flag = 0})
(E,z1,z2)
(E)
(E,{flag = 0})
(E,{z = x},{flag = 0})
(E,z)
(E,z)
(bnf)
(P,{flag = 0},{tech = []})
(P,{tech = []})
(nf,m)
(P,{flag = 0},{tech = []})
(bnf,x)
(bnf,x,{flag = 1})
(bnf,sfu,x)
(bnf,x,{flag = 1})
(bnf,x)
(sbnf)
(bnf)
(bnf)
(bnf)
(bnf,S)
(bnf)
(bnr,subgroup,{flag = 0})
(bnf,ideal,{flag = 0})
(bnf,I)
(bnf,list)
(a_1,{a_2},{a_3}, {flag = 0})
(bnr,chi)
(a1,{a2},{a3},{flag = 0})
(bnf,bound,{arch},{flag = 0})
(bnf,ideal,{flag = 0})
(a1,{a2},{a3})
(bnr,x,{flag = 1})
(bnr,chi,{flag = 0})
{(bnr,subgroup,{flag = 0})}
(nf,b)
(x,t)
(gal,perm,{fl = 0},{v = y}))
(pol,{den})
(gal,perm)
(n,H,{Z},{v})
(nf,x,y)
(nf,x,{y})
(nf,x,{flag = 0})
(nf,x,y)
(nf,x,y)
(nf,x,y,{flag = 0})
(nf,x)
(nf,a,{b})
(nf,x,y)
(nf,x)
(nf,bound,{flag = 4})
(nf,list,{arch = []},{flag = 0})
(nf,x,bid)
(nf,x,{vdir})
(nf,x,y,{flag = 0})
(nf,x)
(nf,x,k,{flag = 0})
(nf,p)
(nf,x)
(nf,I,{vdir = 0})
(nf,I,{flag = 1})
(nf,x,{a})
(nf,x,vp)
(nf,x)
(nf,x)
(nf,x)
(a)
(x,p)
(nf,x)
(x,{flag = 0},{p})
(nf,x)
(nf,x)
(x,{flag = 0},{p})
(nf,x,y)
(nf,x,y)
(nf,x,y,pr)
(nf,x,y)
(nf,x,y)
(nf,x,y)
(nf,x,y,pr)
(nf,x,k)
(nf,x,k,pr)
(nf,x,ideal)
(nf,x,pr)
(nf,x,pr)
(nf,x)
(nf,x,pr)
(nf,aut,x)
(nf,{flag = 0},{d})
(nf,a,b,{pr})
(nf,x)
(nf,x,detx)
(pol,{flag = 0})
(nf,x)
(x,y)
(x,y)
(nf)
(nf,a,pr)
(nf,pr)
(nf,{d = 0})
(nf,x)
(nf)
(nf,x)
(nf,a,b,pr)
(x,y,{flag = 0})
(x)
(x,{flag = 0},{p})
(x,{flag = 0})
(x)
(x)
(rnf,x)
(bnf,x)
(rnf,x)
(nf,T,a,{v = x})
(bnf,pol)
(nf,pol,pr)
(nf,M)
(nf,pol)
(rnf,x)
(rnf,x)
(rnf,x)
(rnf,x)
(nf,pol,{flag = 0})
(bnf,x)
(rnf,x)
(rnf,x)
(rnf,x)
(rnf,x,y)
(rnf,x)
(rnf,x)
(rnf,x)
(rnf,x)
(rnf,x)
(nf,pol)
(bnf,x)
(bnf,ext,el,{flag = 1})
(bnr,subgroup,{deg = 0})
(nf,pol,order)
(bnr,pol)
(nf,pol)
(nf,pol,{flag = 0})
(nf,pol)
(nf,x)
(bnr,{bound},{flag = 0})
(znf,x,{flag = 0})
(x)
(a
^
b)
(x,{v})
(x)
(pol,p,r,{flag = 0})
(x,{v})
(pol,a)
(x,s,{v})
(x,{v})
(n,{v = x})
(pol,{v})
(f)
(x, y, p, e)
(xa,{ya},{v = x},{&e})
(pol)
(x,{v})
(n,{v = x})
(pol)
(x,y,{v},{flag = 0})
(pol,{flag = 0})
(pol,p,{flag = 0})
(pol,p,r)
(pol,{a},{b})
(n,d,{v = x})
(x,y)
(x,n)
(n,{v = x})
(n,m)
(x,y)
(x)
(x)
(x,y,z)
(x,y)
(tnf,a,{sol})
(P,{flag = 0})
(x,k,{flag = 0})
(A,{v = x},{flag = 0})
(x,{y})
(x,{flag = 0})
(n)
(list,x,n)
(list)
(list,x,{n})
(list,{flag = 0})
(x)
(x)
(x,{flag = 0})
(x)
(x)
(x)
(x)
(x)
(x,{flag = 0})
(x,d)
(x,d)
(n)
(x,{flag = 0})
(x)
(x)
(x,y)
(x,y)
(x)
(x,{flag = 0})
(x,{flag = 0})
(x,d)
(x,y)
(x,{q})
(x)
(m,n,{X},{Y},{expr = 0})
(x,p)
(x)
(X,{flag = 0})
(x,y)
(m,d,y,{flag = 0})
(x)
(x)
or x~
(q)
(x)
(x,{flag = 0})
(x,{flag = 0})
(x,b,m,{flag = 0})
(x)
(x)
(x,y)
(x)
(x,y)
(x,y,{flag = 0})
(x,y)
(x)
(x,y,{z})
(x,{k},{flag = 0})
(n,{X},{expr = 0})
(n,X,expr)
(X = a,b,expr,{flag = 0})
(X = a,b,expr,{x = 1})
(X = a,b,expr)
(X = a,expr,{flag = 0})
(X = a,b,expr)
(X = a,b,expr,{x = 0})
(X = a,expr,{flag = 0})
(n,X,expr)
(X = a,expr)
(X = a,expr,{flag = 0})
(X = a,b,expr,{Ymin},{Ymax})
(w,x2,y2)
(w)
(w,c)
(w1,w2,dx,dy)
(w)
(list)
(s)
(X = a,b,expr,{flag = 0},{n = 0})
(listx,listy,{flag = 0})
()
(w,x,y)
(w)
(w,X,Y,{flag = 0})
(w,type)
(w,x,y)
(w,X,Y)
(w,size)
(w,type)
(w,dx,dy)
(w,X = a,b,expr,{flag = 0},{n = 0})
(w,data,{flag = 0})
(w,dx,dy)
(w,dx,dy)
(w,dx,dy)
(w,x1,x2,y1,y2)
(w,x,{flag = 0})
(term)
(list)
(X = a,b,expr)
(listx,listy)
libPARI  Functions and Operations Available in PARI and GP
The functions and operators available in PARI and in the GP/PARI calculator are numerous and everexpanding. Here is a description of the ones available in version 2.2.0. It should be noted that many of these functions accept quite different types as arguments, but others are more restricted. The list of acceptable types will be given for each function or class of functions. Except when stated otherwise, it is understood that a function or operation which should make natural sense is legal. In this chapter, we will describe the functions according to a rough classification. The general entry looks something like:
foo(x,{flag = 0})
: short description.
The library syntax is foo(x,flag)
.
This means that the GP function foo
has one mandatory argument x
, and
an optional one, flag
, whose default value is 0 (the {}
should never be
typed, it is just a convenient notation we will use throughout to denote
optional arguments). That is, you can type foo(x,2)
, or foo(x)
,
which is then understood to mean foo(x,0)
. As well, a comma or closing
parenthesis, where an optional argument should have been, signals to GP it
should use the default. Thus, the syntax foo(x,)
is also accepted as a
synonym for our last expression. When a function has more than one optional
argument, the argument list is filled with user supplied values, in order.
And when none are left, the defaults are used instead. Thus, assuming that
foo
's prototype had been
B<foo>({x = 1},{y = 2},{z = 3}),
typing in foo(6,4)
would give
you foo(6,4,3)
. In the rare case when you want to set some far away
flag, and leave the defaults in between as they stand, you can use the
``empty arg'' trick alluded to above: foo(6,,1)
would yield
foo(6,2,1)
. By the way, foo()
by itself yields
foo(1,2,3)
as was to be expected. In this rather special case of a
function having no mandatory argument, you can even omit the ()
: a
standalone foo
would be enough (though we don't really recommend it for
your scripts, for the sake of clarity). In defining GP syntax, we strove
to put optional arguments at the end of the argument list (of course, since
they would not make sense otherwise), and in order of decreasing usefulness
so that, most of the time, you will be able to ignore them.
Binary Flags. For some of these optional
flags, we adopted the customary binary notation as a compact way to
represent many toggles with just one number. Letting (p_0,...,p_n)
be a
list of switches (i.e. of properties which can be assumed to take either
the value 0
or 1
), the number 2^3 + 2^5 = 40
means that p_3
and p_5
have been set (that is, set to 1
), and none of the others were (that is,
they were set to 0). This will usually be announced as ``The binary digits
of flag
mean 1: p_0
, 2: p_1
, 4: p_2
'', and so on, using the
available consecutive powers of 2
.
Pointers. If a parameter in the function prototype is prefixed with a & sign, as in
foo(x,&e)
it means that, besides the normal return value, the variable named
e
may be set as a side effect. When passing the argument, the & sign has
to be typed in explicitly. As of version 2.2.0, this pointer
argument
is optional for all documented functions, hence the & will always appear
between brackets as in issquare
(x,{&e})
.
About library programming. To finish with our generic
simpleminded example, the library function foo
, as defined
above, is seen to have two mandatory arguments, x
and flag (no PARI
mathematical function has been implemented so as to accept a variable
number of arguments). When not mentioned otherwise, the result and
arguments of a function are assumed implicitly to be of type GEN
.
Most other functions return an object of type long
integer in C (see
Chapter 4). The variable or parameter names prec and flag always
denote long
integers.
The entree
type is used by the library to implement iterators (loops,
sums, integrals, etc.) when a formal variable has to successively assume a
number of values in a given set. When programming with the library, it is
easier and much more efficient to code loops and the like directly. Hence
this type is not documented, although it does appear in a few library
function prototypes below. See Label se:sums for more details.
/
The expressions +
x
and 
x
refer
to monadic operators (the first does nothing, the second negates x
).
The library syntax is gneg(x)
for 
x
.

The expression x
+
y
is the sum and
x

y
is the difference of x
and y
. Among the prominent
impossibilities are addition/subtraction between a scalar type and a vector
or a matrix, between vector/matrices of incompatible sizes and between an
integermod and a real number.
The library syntax is gadd(x,y)
x
+
y
, gsub(x,y)
for x

y
.
The expression x
*
y
is the product of x
and y
. Among the prominent impossibilities are multiplication between
vector/matrices of incompatible sizes, between an integermod and a real
number. Note that because of vector and matrix operations, *
is not
necessarily commutative. Note also that since multiplication between two
column or two row vectors is not allowed, to obtain the scalar product
of two vectors of the same length, you must multiply a line vector by a
column vector, if necessary by transposing one of the vectors (using
the operator ~
or the function mattranspose
, see
Label se:linear_algebra).
If x
and y
are binary quadratic forms, compose them. See also
qfbnucomp
and qfbnupow
.
The library syntax is gmul(x,y)
for x
*
y
. Also available is
gsqr(x)
for x
*
x
(faster of course!).
The expression x
/
y
is the quotient of x
and y
. In addition to the impossibilities for multiplication, note that if
the divisor is a matrix, it must be an invertible square matrix, and in that
case the result is x*y^{1}
. Furthermore note that the result is as exact
as possible: in particular, division of two integers always gives a rational
number (which may be an integer if the quotient is exact) and not the
Euclidean quotient (see x
\
y
for that), and similarly the
quotient of two polynomials is a rational function in general. To obtain the
approximate real value of the quotient of two integers, add 0.
to the
result; to obtain the approximate p
adic value of the quotient of two
integers, add O(p^k)
to the result; finally, to obtain the
Taylor series expansion of the quotient of two polynomials, add
O(X^k)
to the result or use the taylor
function
(see Label se:taylor).
The library syntax is gdiv(x,y)
for x
/
y
.
The expression x
\
y
is the
Euclidean quotient of x
and y
. The types must be either both
integer or both polynomials. The result is the Euclidean quotient. In the
case of integer division, the quotient is such that the corresponding
remainder is nonnegative.
The library syntax is gdivent(x,y)
for x
\
y
.
The expression x
\/
y
is the Euclidean
quotient of x
and y
. The types must be either both integer or both
polynomials. The result is the rounded Euclidean quotient. In the case of
integer division, the quotient is such that the corresponding remainder is
smallest in absolute value and in case of a tie the quotient closest to
+ oo
is chosen.
The library syntax is gdivround(x,y)
for x
\/
y
.
The expression x
%
y
is the
Euclidean remainder of x
and y
. The modulus y
must be of type
integer or polynomial. The result is the remainder, always nonnegative in
the case of integers. Allowed dividend types are scalar exact types when
the modulus is an integer, and polynomials, polmods and rational functions
when the modulus is a polynomial.
The library syntax is gmod(x,y)
for x
%
y
.
(x,y)
creates a column vector with two components,
the first being the Euclidean quotient, the second the Euclidean remainder,
of the division of x
by y
. This avoids the need to do two divisions if
one needs both the quotient and the remainder. The arguments must be both
integers or both polynomials; in the case of integers, the remainder is
nonnegative.
The library syntax is gdiventres(x,y)
.
The expression x^n
is powering.
If the exponent is an integer, then exact operations are performed using
binary (leftshift) powering techniques. In particular, in this case x
cannot be a vector or matrix unless it is a square matrix (and moreover
invertible if the exponent is negative). If x
is a p
adic number, its
precision will increase if v_p(n) > 0
. PARI is able to rewrite the
multiplication x * x
of two identical objects as x^2
, or
sqr(x)
(here, identical means the operands are two different labels
referencing the same chunk of memory; no equality test is performed). This
is no longer true when more than two arguments are involved.
If the exponent is not of type integer, this is treated as a transcendental function (see Label se:trans), and in particular has the effect of componentwise powering on vector or matrices.
As an exception, if the exponent is a rational number p/q
and x
an
integer modulo a prime, return a solution y
of y^q = x^p
if it
exists. Currently, q
must not have large prime factors.
Beware that
? Mod(7,19)^(1/2) %1 = Mod(11, 19)/*is any square root*/ ? sqrt(Mod(7,19)) %2 = Mod(8, 19)/*is the smallest square root*/ ? Mod(7,19)^(3/5) %3 = Mod(1, 19) ? %3^(5/3) %4 = Mod(1, 19)/*Mod(7,19) is just another cubic root*/
The library syntax is gpow(x,n,prec)
for x^n
.
(x,n)
or x
<<
n
( = x
>>
(n)
)shifts
x
componentwise left by n
bits if n >= 0
and right by n
bits if
n < 0
. A left shift by n
corresponds to multiplication by 2^n
. A right
shift of an integer x
by n
corresponds to a Euclidean division of
x
by 2^{n}
with a
remainder of the same sign as x
, hence is not the same (in general) as
x \ 2^n
.
The library syntax is gshift(x,n)
where n
is a long
.
(x,n)
multiplies x
by 2^n
. The difference with
shift
is that when n < 0
, ordinary division takes place, hence for
example if x
is an integer the result may be a fraction, while for
shift
Euclidean division takes place when n < 0
hence if x
is an
integer the result is still an integer.
The library syntax is gmul2n(x,n)
where n
is a long
.
The six standard comparison operators <=
, <
, >=
,
>
, ==
, ! =
are available in GP, and in library mode under
the names gle, glt, gge, ggt, geq, gne
respectively. The library syntax is co(x,y)
, where co is the
comparison operator. The result is 1 (as a GEN
) if the comparison is
true, 0 (as a GEN
) if it is false.
The standard boolean functions 
(inclusive or), &&
(and) and !
(not) are also available, and the
library syntax is gor(x,y)
, gand(x,y)
and gnot(x)
respectively.
In library mode, it is in fact usually preferable to use the two basic
functions which are gcmp(x,y)
which gives the sign (1, 0, or 1) of
xy
, where x
and y
must be in R, and gegal(x,y)
which
can be applied to any two PARI objects x
and y
and gives 1 (i.e. true) if
they are equal (but not necessarily identical), 0 (i.e. false) otherwise.
Particular cases of gegal which should be used are gcmp0(x)
(x == 0
?), gcmp1(x)
(x == 1
?), and
gcmp_1(x)
(x == 1
?).
Note that gcmp0(x)
tests whether x
is equal to zero, even if x
is
not an exact object. To test whether x
is an exact object which is equal to
zero, one must use isexactzero
.
Also note that the gcmp
and gegal
functions return a Cinteger,
and not a GEN
like gle
etc.
GP accepts the following synonyms for some of the above functions: since we
thought it might easily lead to confusion, we don't use the customary C
operators for bitwise and
or bitwise or
(use bitand
or
bitor
), hence 
and &
are accepted as synonyms of 
and &&
respectively.
Also, < >
is accepted as a synonym for ! =
. On the other hand,
=
is definitely not a synonym for ==
since it is the
assignment statement.
(x,y)
gives the result of a lexicographic comparison
between x
and y
. This is to be interpreted in quite a wide sense. For
example, the vector [1,3]
will be considered smaller than the longer
vector [1,3,1]
(but of course larger than [1,2,5]
),
i.e. lex([1,3], [1,3,1])
will return 1
.
The library syntax is lexcmp(x,y)
.
(x)
sign (0
, 1
or 1
) of x
, which must be of
type integer, real or fraction.
The library syntax is gsigne(x)
. The result is a long
.
(x,y)
and min(x,y)
creates the
maximum and minimum of x
and y
when they can be compared.
The library syntax is gmax(x,y)
and gmin(x,y)
.
(x)
if x
is a vector or a matrix, returns the maximum
of the elements of x
, otherwise returns a copy of x
. Returns  oo
in the form of (2^{31}1)
(or (2^{63}1)
for 64bit machines) if x
is
empty.
The library syntax is vecmax(x)
.
(x)
if x
is a vector or a matrix, returns the minimum
of the elements of x
, otherwise returns a copy of x
. Returns + oo
in the form of 2^{31}1
(or 2^{63}1
for 64bit machines) if x
is empty.
The library syntax is vecmin(x)
.
Many of the conversion functions are rounding or truncating operations. In this case, if the argument is a rational function, the result is the Euclidean quotient of the numerator by the denominator, and if the argument is a vector or a matrix, the operation is done componentwise. This will not be restated for every function.
({x = []})
transforms a (row or column) vector x
into a list. The only other way to create a t_LIST
is to use the
function listcreate
.
This is useless in library mode.
({x = []})
transforms the object x
into a matrix.
If x
is not a vector or a matrix, this creates a 1 x 1
matrix.
If x
is a row (resp. column) vector, this creates a 1row (resp.
1column) matrix. If x
is already a matrix, a copy of x
is created.
This function can be useful in connection with the function concat
(see there).
The library syntax is gtomat(x)
.
(x,y,{flag = 0})
creates the PARI object
(x mod y)
, i.e. an integermod or a polmod. y
must be an integer or a
polynomial. If y
is an integer, x
must be an integer, a rational
number, or a p
adic number compatible with the modulus y
. If y
is a
polynomial, x
must be a scalar (which is not a polmod), a polynomial, a
rational function, or a power series.
This function is not the same as x
%
y
, the result of which is an
integer or a polynomial.
If flag
is equal to 1
, the modulus of the created result is put on the
heap and not on the stack, and hence becomes a permanent copy which cannot be
erased later by garbage collecting (see Label se:garbage). Functions
will operate faster on such objects and memory consumption will be lower.
On the other hand, care should be taken to avoid creating too many such
objects.
Under GP, the same effect can be obtained by assigning the object to a GP variable (the value of which is a permanent object for the duration of the relevant library function call, and is treated as such). This value is subject to garbage collection, since it will be deleted when the value changes. This is preferable and the above flag is only retained for compatibility reasons (it can still be useful in library mode).
The library syntax is Mod0(x,y,flag)
. Also available are
*
for flag = 1
: gmodulo(x,y)
.
*
for flag = 0
: gmodulcp(x,y)
.
(x,{v = x})
transforms the object x
into a polynomial with
main variable v
. If x
is a scalar, this gives a constant polynomial. If
x
is a power series, the effect is identical to truncate
(see there),
i.e. it chops off the O(X^k)
. If x
is a vector, this function creates
the polynomial whose coefficients are given in x
, with x[1]
being the
leading coefficient (which can be zero).
Warning: this is not a substitution function. It is intended to be
quick and dirty. So if you try Pol(a,y)
on the polynomial a = x+y
,
you will get y+y
, which is not a valid PARI object.
The library syntax is gtopoly(x,v)
, where v
is a variable number.
(x,{v = x})
transform the object x
into a polynomial
with main variable v
. If x
is a scalar, this gives a constant polynomial.
If x
is a power series, the effect is identical to truncate
(see
there), i.e. it chops off the O(X^k)
. If x
is a vector, this function
creates the polynomial whose coefficients are given in x
, with x[1]
being
the constant term. Note that this is the reverse of Pol
if x
is a
vector, otherwise it is identical to Pol
.
The library syntax is gtopolyrev(x,v)
, where v
is a variable number.
(a,b,c,{D = 0.})
creates the binary quadratic form
ax^2+bxy+cy^2
. If b^24ac > 0
, initialize Shanks' distance
function to D
.
The library syntax is Qfb0(a,b,c,D,prec)
. Also available are
qfi(a,b,c)
(when b^24ac < 0
), and
qfr(a,b,c,d)
(when b^24ac > 0
).
(x,{v = x})
transforms the object x
into a power series
with main variable v
(x
by default). If x
is a scalar, this gives a
constant power series with precision given by the default serieslength
(corresponding to the C global variable precdl
). If x
is a
polynomial, the precision is the greatest of precdl
and the degree of
the polynomial. If x
is a vector, the precision is similarly given, and the
coefficients of the vector are understood to be the coefficients of the power
series starting from the constant term (i.e. the reverse of the function
Pol
).
The warning given for Pol
applies here: this is not a substitution
function.
The library syntax is gtoser(x,v)
, where v
is a variable number (i.e. a C integer).
({x = []})
converts x
into a set, i.e. into a row vector
with strictly increasing entries. x
can be of any type, but is most useful
when x
is already a vector. The components of x
are put in canonical form
(type t_STR
) so as to be easily sorted. To recover an ordinary GEN
from such an element, you can apply eval
to it.
The library syntax is gtoset(x)
.
({x = ""},{flag = 0})
converts x
into a
character string (type t_STR
, the empty string if x
is omitted). To
recover an ordinary GEN
from a string, apply eval
to it. The
arguments of Str
are evaluated in string context (see
Label se:strings). If flag is set, treat x
as a filename and perform
environment expansion on the string. This feature can be used to read
environment variable values.
? i = 1; Str("x" i) %1 = "x1" ? eval(%) %2 = x1; ? Str("$HOME", 1) %3 = "/home/pari"
The library syntax is strtoGENstr(x,flag)
. This function is mostly useless in library mode. Use
the pair strtoGEN
/GENtostr
to convert between char*
and
GEN
.
({x = []})
transforms the object x
into a row vector. The
vector will be with one component only, except when x
is a vector/matrix or
a quadratic form (in which case the resulting vector is simply the initial
object considered as a row vector), but more importantly when x
is a
polynomial or a power series. In the case of a polynomial, the coefficients
of the vector start with the leading coefficient of the polynomial, while
for power series only the significant coefficients are taken into account,
but this time by increasing order of degree.
The library syntax is gtovec(x)
.
(x)
outputs the vector of the binary digits of x
.
Here x
can be an integer, a real number (in which case the result has two
components, one for the integer part, one for the fractional part) or a
vector/matrix.
The library syntax is binaire(x)
.
(x,y)
bitwise and
of two
integers x
and y
, that is the integer
sum (x_i and y_i) 2^i
Negative numbers behave as if modulo a huge power of 2
.
The library syntax is gbitand(x,y)
.
(x,{n = 1})
bitwise negation of an integer x
,
truncated to n
bits, that is the integer
sum_{i = 0}^n not(x_i) 2^i
The special case n = 1
means no truncation: an infinite sequence of
leading 1
is then represented as a negative number.
Negative numbers behave as if modulo a huge power of 2
.
The library syntax is gbitneg(x)
.
(x,y)
bitwise negated imply of two integers x
and y
(or not
(x ==> y)
), that is the integer
sum (x_i and not(y_i)) 2^i
Negative numbers behave as if modulo a huge power of 2
.
The library syntax is gbitnegimply(x,y)
.
(x,y)
bitwise (inclusive) or
of two integers x
and y
, that is the integer
sum (x_i or y_i) 2^i
Negative numbers behave as if modulo a huge power of 2
.
The library syntax is gbitor(x,y)
.
(x,n)
outputs the n^{th}
bit of x
starting
from the right (i.e. the coefficient of 2^n
in the binary expansion of x
).
The result is 0 or 1. To extract several bits at once as a vector, pass a
vector for n
.
The library syntax is bittest(x,n)
, where n
and the result are long
s.
(x,y)
bitwise (exclusive) or
of two integers x
and y
, that is the integer
sum (x_i xor y_i) 2^i
Negative numbers behave as if modulo a huge power of 2
.
The library syntax is gbitxor(x,y)
.
(x)
ceiling of x
. When x
is in R,
the result is the smallest integer greater than or equal to x
. Applied to a
rational function, ceil(x)
returns the euclidian quotient of the
numerator by the denominator.
The library syntax is gceil(x)
.
(x,{v})
lifts an element x = a mod n
of Z/nZ
to a
in Z, and similarly lifts a polmod to a polynomial. This is the
same as lift
except that in the particular case of elements of
Z/nZ
, the lift y
is such that n/2 < y <= n/2
. If x
is of type
fraction, complex, quadratic, polynomial, power series, rational function,
vector or matrix, the lift is done for each coefficient. Real and p
adics
are forbidden.
The library syntax is centerlift0(x,v)
, where v
is a long
and an omitted v
is coded
as 1
. Also available is centerlift(x)
= centerlift0(x,1)
.
(x,y)
creates a copy of the object x
where its
variables are modified according to the permutation specified by the vector
y
. For example, assume that the variables have been introduced in the
order x
, a
, b
, c
. Then, if y
is the vector
[x,c,a,b]
, the variable a
will be replaced by c
, b
by
a
, and c
by b
, x
being unchanged. Note that the
permutation must be completely specified, e.g. [c,a,b]
would not work,
since this would replace x
by c
, and leave a
and b
unchanged (as well as c
which is the fourth variable of the initial
list). In particular, the new variable names must be distinct.
The library syntax is changevar(x,y)
.
There are essentially three ways to extract the components from a PARI object.
The first and most general, is the function component(x,n)
which
extracts the n^{th}
component of x
. This is to be understood as
follows: every PARI type has one or two initial code words. The
components are counted, starting at 1, after these code words. In particular
if x
is a vector, this is indeed the n^{th}
component of x
, if
x
is a matrix, the n^{th}
column, if x
is a polynomial, the
n^{th}
coefficient (i.e. of degree n1
), and for power series, the
n^{th}
significant coefficient. The use of the function
component
implies the knowledge of the structure of the different PARI
types, which can be recalled by typing \t
under GP.
The library syntax is compo(x,n)
, where n
is a long
.
The two other methods are more natural but more restricted. The function
polcoeff(x,n)
gives the coefficient of degree n
of the polynomial
or power series x
, with respect to the main variable of x
(to check
variable ordering, or to change it, use the function reorder
, see
Label se:reorder). In particular if n
is less than the valuation of
x
or in the case of a polynomial, greater than the degree, the result is
zero (contrary to compo
which would send an error message). If x
is
a power series and n
is greater than the largest significant degree, then
an error message is issued.
For greater flexibility, vector or matrix types are also accepted for x
,
and the meaning is then identical with that of compo
.
Finally note that a scalar type is considered by polcoeff
as a
polynomial of degree zero.
The library syntax is truecoeff(x,n)
.
The third method is specific to vectors or matrices under GP. If x
is a
(row or column) vector, then x[n]
represents the n^{th}
component of x
, i.e. compo(x,n)
. It is more natural and shorter to
write. If x
is a matrix, x[m,n]
represents the coefficient of
row m
and column n
of the matrix, x[m,]
represents
the m^{th}
row of x
, and x[,n]
represents
the n^{th}
column of x
.
Finally note that in library mode, the macros coeff and mael
are available to deal with the nonrecursivity of the GEN
type from the
compiler's point of view. See the discussion on typecasts in Chapter 4.
(x)
conjugate of x
. The meaning of this
is clear, except that for real quadratic numbers, it means conjugation in the
real quadratic field. This function has no effect on integers, reals,
integermods, fractions or p
adics. The only forbidden type is polmod
(see conjvec
for this).
The library syntax is gconj(x)
.
(x)
conjugate vector representation of x
. If x
is a
polmod, equal to Mod
(a,q)
, this gives a vector of length
degree(q)
containing the complex embeddings of the polmod if q
has
integral or rational coefficients, and the conjugates of the polmod if q
has some integermod coefficients. The order is the same as that of the
polroots
functions. If x
is an integer or a rational number, the
result is x
. If x
is a (row or column) vector, the result is a matrix
whose columns are the conjugate vectors of the individual elements of x
.
The library syntax is conjvec(x,prec)
.
(x)
lowest denominator of x
. The meaning of this
is clear when x
is a rational number or function. When x
is an integer
or a polynomial, the result is equal to 1
. When x
is a vector or a matrix,
the lowest common denominator of the components of x
is computed. All other
types are forbidden.
The library syntax is denom(x)
.
(x)
floor of x
. When x
is in R, the result is the
largest integer smaller than or equal to x
. Applied to a rational function,
floor(x)
returns the euclidian quotient of the numerator by the
denominator.
The library syntax is gfloor(x)
.
(x)
fractional part of x
. Identical to
xfloor(x)
. If x
is real, the result is in [0,1[
.
The library syntax is gfrac(x)
.
(x)
imaginary part of x
. When
x
is a quadratic number, this is the coefficient of omega
in
the ``canonical'' integral basis (1,omega)
.
The library syntax is gimag(x)
.
(x)
number of noncode words in x
really used (i.e. the
effective length minus 2 for integers and polynomials). In particular,
the degree of a polynomial is equal to its length minus 1. If x
has type
t_STR
, output number of letters.
The library syntax is glength(x)
and the result is a C long.
(x,{v})
lifts an element x = a mod n
of Z/nZ
to
a
in Z, and similarly lifts a polmod to a polynomial if v
is omitted.
Otherwise, lifts only polmods with main variable v
(if v
does not occur
in x
, lifts only intmods). If x
is of type fraction, complex, quadratic,
polynomial, power series, rational function, vector or matrix, the lift is
done for each coefficient. Forbidden types for x
are reals and p
adics.
The library syntax is lift0(x,v)
, where v
is a long
and an omitted v
is coded as
1
. Also available is lift(x)
= lift0(x,1)
.
(x)
algebraic norm of x
, i.e. the product of x
with
its conjugate (no square roots are taken), or conjugates for polmods. For
vectors and matrices, the norm is taken componentwise and hence is not the
L^2
norm (see norml2
). Note that the norm of an element of
R is its square, so as to be compatible with the complex norm.
The library syntax is gnorm(x)
.
(x)
square of the L^2
norm of x
. x
must
be a (row or column) vector.
The library syntax is gnorml2(x)
.
(x)
numerator of x
. When x
is a rational number
or function, the meaning is clear. When x
is an integer or a polynomial,
the result is x
itself. When x
is a vector or a matrix, then
numerator(x)
is defined to be denominator(x)*x
. All other types
are forbidden.
The library syntax is numer(x)
.
(n,k)
generates the k
th permutation (as a
row vector of length n
) of the numbers 1
to n
. The number k
is taken
modulo n!
, i.e. inverse function of permtonum
.
The library syntax is permute(n,k)
, where n
is a long
.
(x,p)
absolute p
adic precision of the object x
.
This is the minimum precision of the components of x
. The result is
VERYBIGINT
(2^{31}1
for 32bit machines or 2^{63}1
for 64bit
machines) if x
is an exact object.
The library syntax is padicprec(x,p)
and the result is a long
integer.
(x)
given a permutation x
on n
elements,
gives the number k
such that x = numtoperm(n,k)
, i.e. inverse
function of numtoperm
.
The library syntax is permuteInv(x)
.
(x,{n})
gives the precision in decimal digits of the
PARI object x
. If x
is an exact object, the largest single precision
integer is returned. If n
is not omitted, creates a new object equal to x
with a new precision n
. This is to be understood as follows:
For exact types, no change. For x
a vector or a matrix, the operation
is done componentwise.
For real x
, n
is the number of desired significant decimal digits.
If n
is smaller than the precision of x
, x
is truncated, otherwise x
is extended with zeros.
For x
a p
adic or a power series, n
is the desired number of
significant p
adic or X
adic digits, where X
is the main variable of
x
.
Note that the function precision
never changes the type of the result.
In particular it is not possible to use it to obtain a polynomial from a
power series. For that, see truncate
.
The library syntax is precision0(x,n)
, where n
is a long
. Also available are
ggprecision(x)
(result is a GEN
) and gprec(x,n)
, where
n
is a long
.
({N = 2^{31}})
gives a random integer between 0 and
N1
. N
can be arbitrary large. This is an internal PARI function and does
not depend on the system's random number generator. Note that the resulting
integer is obtained by means of linear congruences and will not be well
distributed in arithmetic progressions.
The library syntax is genrand(N)
.
(x)
real part of x
. In the case where x
is a quadratic
number, this is the coefficient of 1
in the ``canonical'' integral basis
(1,omega)
.
The library syntax is greal(x)
.
(x,{&e})
If x
is in R, rounds x
to the nearest
integer and sets e
to the number of error bits, that is the binary exponent
of the difference between the original and the rounded value (the
``fractional part''). If the exponent of x
is too large compared to its
precision (i.e. e > 0
), the result is undefined and an error occurs if e
was not given.
Important remark: note that, contrary to the other truncation functions, this function operates on every coefficient at every level of a PARI object. For example
truncate((2.4*X^21.7)/(X)) = 2.4*X,
whereas
round((2.4*X^21.7)/(X)) = (2*X^22)/(X).
An important use of round
is to get exact results after a long
approximate computation, when theory tells you that the coefficients
must be integers.
The library syntax is grndtoi(x,&e)
, where e
is a long
integer. Also available is
ground(x)
.
(x)
this function tries to simplify the object x
as
much as it can. The simplifications do not concern rational functions (which
PARI automatically tries to simplify), but type changes. Specifically, a
complex or quadratic number whose imaginary part is exactly equal to 0
(i.e. not a real zero) is converted to its real part, and a polynomial of
degree zero is converted to its constant term. For all types, this of course
occurs recursively. This function is useful in any case, but in particular
before the use of arithmetic functions which expect integer arguments, and
not for example a complex number of 0 imaginary part and integer real part
(which is however printed as an integer).
The library syntax is simplify(x)
.
(x)
outputs the total number of bytes occupied by the
tree representing the PARI object x
.
The library syntax is taille2(x)
which returns a long
. The
function taille returns the number of words instead.
(x)
outputs a quick bound for the number of decimal
digits of (the components of) x
, off by at most 1
. If you want the
exact value, you can use length(Str(x))
, which is much slower.
The library syntax is sizedigit(x)
which returns a long
.
(x,{&e})
truncates x
and sets e
to the number of
error bits. When x
is in R, this means that the part after the decimal
point is chopped away, e
is the binary exponent of the difference between
the original and the truncated value (the ``fractional part''). If the
exponent of x
is too large compared to its precision (i.e. e > 0
), the
result is undefined and an error occurs if e
was not given. The function
applies componentwise on rational functions and vector / matrices; e
is
then the maximal number of error bits.
Note a very special use of truncate
: when applied to a power series, it
transforms it into a polynomial or a rational function with denominator
a power of X
, by chopping away the O(X^k)
. Similarly, when applied to
a p
adic number, it transforms it into an integer or a rational number
by chopping away the O(p^k)
.
The library syntax is gcvtoi(x,&e)
, where e
is a long
integer. Also available is
gtrunc(x)
.
(x,p)
computes the highest
exponent of p
dividing x
. If p
is of type integer, x
must be an
integer, an integermod whose modulus is divisible by p
, a fraction, a
q
adic number with q = p
, or a polynomial or power series in which case the
valuation is the minimum of the valuation of the coefficients.
If p
is of type polynomial, x
must be of type polynomial or rational
function, and also a power series if x
is a monomial. Finally, the
valuation of a vector, complex or quadratic number is the minimum of the
component valuations.
If x = 0
, the result is VERYBIGINT
(2^{31}1
for 32bit machines or
2^{63}1
for 64bit machines) if x
is an exact object. If x
is a
p
adic numbers or power series, the result is the exponent of the zero.
Any other type combinations gives an error.
The library syntax is ggval(x,p)
, and the result is a long
.
(x)
gives the main variable of the object x
, and
p
if x
is a p
adic number. Gives an error if x
has no variable
associated to it. Note that this function is useful only in GP, since in
library mode the function gvar
is more appropriate.
The library syntax is gpolvar(x)
. However, in library mode, this function should not be used.
Instead, test whether x
is a p
adic (type t_PADIC
), in which case p
is in x[2]
, or call the function gvar(x)
which returns the variable
number of x
if it exists, BIGINT
otherwise.
As a general rule, which of course in some cases may have exceptions, transcendental functions operate in the following way:
*
If the argument is either an integer, a real, a rational, a complex
or a quadratic number, it is, if necessary, first converted to a real (or
complex) number using the current precision held in the default
realprecision
. Note that only exact arguments are converted, while
inexact arguments such as reals are not.
Under GP this is transparent to the user, but when programming in library mode, care must be taken to supply a meaningful parameter prec as the last argument of the function if the first argument is an exact object. This parameter is ignored if the argument is inexact.
Note that in library mode the precision argument prec is a word
count including codewords, i.e. represents the length in words of a real
number, while under GP the precision (which is changed by the metacommand
\p
or using default(realprecision,...)
) is the number of significant
decimal digits.
Note that some accuracies attainable on 32bit machines cannot be attained on 64bit machines for parity reasons. For example the default GP accuracy is 28 decimal digits on 32bit machines, corresponding to prec having the value 5, but this cannot be attained on 64bit machines.
After possible conversion, the function is computed. Note that even if the
argument is real, the result may be complex (e.g. acos(2.0)
or
acosh(0.0)
). Note also that the principal branch is always chosen.
*
If the argument is an integermod or a p
adic, at present only a
few functions like sqrt
(square root), sqr
(square), log
,
exp
, powering, teichmuller
(Teichmüller character) and
agm
(arithmeticgeometric mean) are implemented.
Note that in the case of a 2
adic number, sqr(x)
may not be
identical to x*x
: for example if x = 1+O(2^5)
and y = 1+O(2^5)
then
x*y = 1+O(2^5)
while sqr(x) = 1+O(2^6)
. Here, x * x
yields the
same result as sqr(x)
since the two operands are known to be
identical. The same statement holds true for p
adics raised to the power
n
, where v_p(n) > 0
.
Remark: note that if we wanted to be strictly consistent with
the PARI philosophy, we should have x*y = (4 mod 8)
and sqr(x) =
(4 mod 32)
when both x
and y
are congruent to 2
modulo 4
.
However, since integermod is an exact object, PARI assumes that the modulus
must not change, and the result is hence (0 mod 4)
in both cases. On
the other hand, p
adics are not exact objects, hence are treated
differently.
*
If the argument is a polynomial, power series or rational function,
it is, if necessary, first converted to a power series using the current
precision held in the variable precdl
. Under GP this again is
transparent to the user. When programming in library mode, however, the
global variable precdl
must be set before calling the function if the
argument has an exact type (i.e. not a power series). Here precdl
is
not an argument of the function, but a global variable.
Then the Taylor series expansion of the function around X = 0
(where X
is
the main variable) is computed to a number of terms depending on the number
of terms of the argument and the function being computed.
*
If the argument is a vector or a matrix, the result is the
componentwise evaluation of the function. In particular, transcendental
functions on square matrices, which are not implemented in the present
version 2.2.0 (see Appendix B however), will have a slightly different name
if they are implemented some day.
If y
is not of type integer, x^y
has the same
effect as exp(y*ln(x))
. It can be applied to p
adic numbers as
well as to the more usual types.
The library syntax is gpow(x,y,prec)
.
Euler's constant 0.57721...
. Note that Euler
is one of the few special reserved names which cannot be used for variables
(the others are I
and Pi
, as well as all function names).
The library syntax is mpeuler(prec)
where prec
must be given. Note that
this creates gamma
on the PARI stack, but a copy is also created on the
heap for quicker computations next time the function is called.
the complex number sqrt {1}
.
The library syntax is the global variable gi
(of type GEN
).
the constant Pi
(3.14159...
).
The library syntax is mppi(prec)
where prec
must be given. Note that this
creates Pi
on the PARI stack, but a copy is also created on the heap for
quicker computations next time the function is called.
(x)
absolute value of x
(modulus if x
is complex).
Power series and rational functions are not allowed. Contrary to most
transcendental functions, an exact argument is not converted to a real
number before applying abs
and an exact result is returned if possible.
? abs(1) %1 = 1 ? abs(3/7 + 4/7*I) %2 = 5/7 ? abs(1 + I) %3 = 1.414213562373095048801688724
If x
is a polynomial, returns x
if the leading coefficient is
real and negative else returns x
. For a power series, the constant
coefficient is considered instead.
The library syntax is gabs(x,prec)
.
(x)
principal branch of cos^{1}(x)
,
i.e. such that Re(acos(x)) belongs to [0,Pi]
. If
x belongs to R
and x > 1
, then acos(x)
is complex.
The library syntax is gacos(x,prec)
.
(x)
principal branch of cosh^{1}(x)
,
i.e. such that Im(acosh(x)) belongs to [0,Pi]
. If
x belongs to R
and x < 1
, then acosh(x)
is complex.
The library syntax is gach(x,prec)
.
(x,y)
arithmeticgeometric mean of x
and y
. In the
case of complex or negative numbers, the principal square root is always
chosen. p
adic or power series arguments are also allowed. Note that
a p
adic agm exists only if x/y
is congruent to 1 modulo p
(modulo
16 for p = 2
). x
and y
cannot both be vectors or matrices.
The library syntax is agm(x,y,prec)
.
(x)
argument of the complex number x
, such that
Pi < arg(x) <= Pi
.
The library syntax is garg(x,prec)
.
(x)
principal branch of sin^{1}(x)
, i.e. such
that Re(asin(x)) belongs to [Pi/2,Pi/2]
. If x belongs to R
and x > 1
then
asin(x)
is complex.
The library syntax is gasin(x,prec)
.
(x)
principal branch of sinh^{1}(x)
, i.e. such
that Im(asinh(x)) belongs to [Pi/2,Pi/2]
.
The library syntax is gash(x,prec)
.
(x)
principal branch of tan^{1}(x)
, i.e. such
that Re(atan(x)) belongs to ]Pi/2,Pi/2[
.
The library syntax is gatan(x,prec)
.
(x)
principal branch of tanh^{1}(x)
, i.e. such
that Im(atanh(x)) belongs to ]Pi/2,Pi/2]
. If x belongs to R
and x > 1
then
atanh(x)
is complex.
The library syntax is gath(x,prec)
.
(x)
Bernoulli number B_x
,
where B_0 = 1
, B_1 = 1/2
, B_2 = 1/6
,..., expressed as a rational number.
The argument x
should be of type integer.
The library syntax is bernfrac(x)
.
(x)
Bernoulli number
B_x
, as bernfrac
, but B_x
is returned as a real number
(with the current precision).
The library syntax is bernreal(x,prec)
.
(x)
creates a vector containing, as rational numbers,
the Bernoulli numbers B_0
, B_2
,..., B_{2x}
. These Bernoulli
numbers can then be used as follows. Assume that this vector has been put
into a variable, say bernint
. Then you can define under GP:
bern(x) = { if (x == 1, return(1/2)); if (x < 0  x % 2, return(0)); bernint[x/2+1] }
and then bern(k)
gives the Bernoulli number of index k
as a
rational number, exactly as bernreal(k)
gives it as a real number. If
you need only a few values, calling bernfrac(k)
each time will be much
more efficient than computing the huge vector above.
The library syntax is bernvec(x)
.
(n,x)
J
Bessel function of half integral index.
More precisely, besseljh(n,x)
computes J_{n+1/2}(x)
where n
must be of type integer, and x
is any element of C. In the
present version 2.2.0, this function is not very accurate when x
is
small.
The library syntax is jbesselh(n,x,prec)
.
(nu,x,{flag = 0})
K
Bessel function of index
nu (which can be complex) and argument x
. Only real and positive
arguments
x
are allowed in the present version 2.2.0. If flag
is equal to 1,
uses another implementation of this function which is often faster.
The library syntax is kbessel(nu,x,prec)
and
kbessel2(nu,x,prec)
respectively.
(x)
cosine of x
.
The library syntax is gcos(x,prec)
.
(x)
hyperbolic cosine of x
.
The library syntax is gch(x,prec)
.
(x)
cotangent of x
.
The library syntax is gcotan(x,prec)
.
(x)
principal branch of the dilogarithm of x
,
i.e. analytic continuation of the power series log _2(x) = sum_{n >= 1}x^n/n^2
.
The library syntax is dilog(x,prec)
.
(x,{n})
exponential integral
int_x^ oo (e^{t})/(t)dt
(x belongs to R
)
If n
is present, outputs the n
dimensional vector
[eint1(x),...,eint1(nx)]
(x >= 0
). This is faster than
repeatedly calling eint1(i * x)
.
The library syntax is veceint1(x,n,prec)
. Also available is
eint1(x,prec)
.
(x)
complementary error function
(2/ sqrt Pi)int_x^ oo e^{t^2}dt
.
The library syntax is erfc(x,prec)
.
(x,{flag = 0})
Dedekind's eta
function, without the
q^{1/24}
. This means the following: if x
is a complex number with positive
imaginary part, the result is prod_{n = 1}^ oo (1q^n)
, where
q = e^{2iPi x}
. If x
is a power series (or can be converted to a power
series) with positive valuation, the result is prod_{n = 1}^ oo (1x^n)
.
If flag = 1
and x
can be converted to a complex number (i.e. is not a power
series), computes the true eta
function, including the leading q^{1/24}
.
The library syntax is eta(x,prec)
.
(x)
exponential of x
.
p
adic arguments with positive valuation are accepted.
The library syntax is gexp(x,prec)
.
(x)
gamma function evaluated at the argument
x+1/2
. When x
is an integer, this is much faster than using
gamma(x+1/2)
.
The library syntax is ggamd(x,prec)
.
(x)
gamma function of x
. In the present version
2.2.0 the p
adic gamma function is not implemented.
The library syntax is ggamma(x,prec)
.
(a,b,x)
U
confluent hypergeometric function with
parameters a
and b
. The parameters a
and b
can be complex but
the present implementation requires x
to be positive.
The library syntax is hyperu(a,b,x,prec)
.
(s,x,{y})
incomplete gamma function.
x
must be positive and s
real. The result returned is int_x^ oo
e^{t}t^{s1}dt
. When y
is given, assume (of course without checking!)
that y = Gamma(s)
. For small x
, this will tremendously speed up the
computation.
The library syntax is incgam(s,x,prec)
and incgam4(s,x,y,prec)
,
respectively. There exist also the functions incgam1 and
incgam2 which are used for internal purposes.
(s,x)
complementary incomplete gamma function.
The arguments s
and x
must be positive. The result returned is
int_0^x e^{t}t^{s1}dt
, when x
is not too large.
The library syntax is incgam3(s,x,prec)
.
(x,{flag = 0})
principal branch of the natural logarithm of
x
, i.e. such that Im(ln(x)) belongs to ]Pi,Pi]
. The result is complex
(with imaginary part equal to Pi
) if x belongs to R
and x < 0
.
p
adic arguments are also accepted for x
, with the convention that
ln (p) = 0
. Hence in particular exp ( ln (x))/x
will not in general be
equal to 1 but to a (p1)
th root of unity (or +1
if p = 2
)
times a power of p
.
If flag
is equal to 1, use an agm formula suggested by Mestre, when x
is
real, otherwise identical to log
.
The library syntax is glog(x,prec)
or glogagm(x,prec)
.
(x)
principal branch of the logarithm of the gamma
function of x
. Can have much larger arguments than gamma
itself.
In the present version 2.2.0, the p
adic lngamma
function is not
implemented.
The library syntax is glngamma(x,prec)
.
(m,x,{flag = 0})
one of the different polylogarithms, depending on flag:
If flag = 0
or is omitted: m^th
polylogarithm of x
, i.e. analytic
continuation of the power series Li_m(x) = sum_{n >= 1}x^n/n^m
. The
program uses the power series when x^2 <= 1/2
, and the power series
expansion in log (x)
otherwise. It is valid in a large domain (at least
x < 230
), but should not be used too far away from the unit circle since it
is then better to use the functional equation linking the value at x
to the
value at 1/x
, which takes a trivial form for the variant below. Power
series, polynomial, rational and vector/matrix arguments are allowed.
For the variants to follow we need a notation: let Re _m
denotes Re
or Im
depending whether m
is odd or even.
If flag = 1
: modified m^th
polylogarithm of x
, called
~ D_m(x)
in Zagier, defined for x <= 1
by
Re _m(sum_{k = 0}^{m1} (( log x)^k)/(k!)Li_{mk}(x)
+(( F<log> x)^{m1})/(m!) F<log> 1x).
If flag = 2
: modified m^th
polylogarithm of x
,
called D_m(x)
in Zagier, defined for x <= 1
by
Re _m(sum_{k = 0}^{m1}(( log x)^k)/(k!)Li_{mk}(x)
(1)/(2)(( F<log> x)^m)/(m!)).
If flag = 3
: another modified m^th
polylogarithm of x
, called P_m(x)
in Zagier, defined for x <= 1
by
Re _m(sum_{k = 0}^{m1}(2^kB_k)/(k!)( log x)^kLi_{mk}(x)
(2^{m1}B_m)/(m!)( F<log> x)^m).
These three functions satisfy the functional equation
f_m(1/x) = (1)^{m1}f_m(x)
.
The library syntax is polylog0(m,x,flag,prec)
.
(x)
the psi
function of x
, i.e. the
logarithmic derivative Gamma'(x)/Gamma(x)
.
The library syntax is gpsi(x,prec)
.
(x)
sine of x
.
The library syntax is gsin(x,prec)
.
(x)
hyperbolic sine of x
.
The library syntax is gsh(x,prec)
.
(x)
square of x
. This operation is not completely
straightforward, i.e. identical to x * x
, since it can usually be
computed more efficiently (roughly onehalf of the elementary
multiplications can be saved). Also, squaring a 2
adic number increases
its precision. For example,
? (1 + O(2^4))^2 %1 = 1 + O(2^5) ? (1 + O(2^4)) * (1 + O(2^4)) %2 = 1 + O(2^4)
Note that this function is also called whenever one multiplies two objects which are known to be identical, e.g. they are the value of the same variable, or we are computing a power.
? x = (1 + O(2^4)); x * x %3 = 1 + O(2^5) ? (1 + O(2^4))^4 %4 = 1 + O(2^6)
(note the difference between %2
and %3
above).
The library syntax is gsqr(x)
.
(x)
principal branch of the square root of x
,
i.e. such that Arg(sqrt(x)) belongs to ]Pi/2, Pi/2]
, or in other
words such that Re (sqrt(x)) > 0
or Re (sqrt(x)) = 0
and
Im (sqrt(x)) >= 0
. If x belongs to R
and x < 0
, then the result is
complex with positive imaginary part.
Integermod a prime and p
adics are allowed as arguments. In that case,
the square root (if it exists) which is returned is the one whose
first p
adic digit (or its unique p
adic digit in the case of
integermods) is in the interval [0,p/2]
. When the argument is an
integermod a nonprime (or a nonprimeadic), the result is undefined.
The library syntax is gsqrt(x,prec)
.
(x,n,{&z})
principal branch of the n
th root of x
,
i.e. such that Arg(sqrt(x)) belongs to ]Pi/n, Pi/n]
.
Integermod a prime and p
adics are allowed as arguments.
If z
is present, it is set to a suitable root of unity allowing to
recover all the other roots. If it was not possible, z is
set to zero.
The following script computes all roots in all possible cases:
sqrtnall(x,n)= { local(V,r,z,r2); r = sqrtn(x,n, &z); if (!z, error("Impossible case in sqrtn")); if (type(x) == "t_INTMOD"  type(x)=="t_PADIC" , r2 = r*z; n = 1; while (r2!=r, r2*=z;n++)); V = vector(n); V[1] = r; for(i=2, n, V[i] = V[i1]*z); V } addhelp(sqrtnall,"sqrtnall(x,n):compute the vector of nthroots of x");
The library syntax is gsqrtn(x,n,&z,prec)
.
(x)
tangent of x
.
The library syntax is gtan(x,prec)
.
(x)
hyperbolic tangent of x
.
The library syntax is gth(x,prec)
.
(x)
Teichmüller character of the p
adic number
x
.
The library syntax is teich(x)
.
(q,z)
Jacobi sine thetafunction.
The library syntax is theta(q,z,prec)
.
(q,k)
k
th derivative at z = 0
of
theta(q,z)
.
The library syntax is thetanullk(q,k,prec)
, where k
is a long
.
(x,{flag = 0})
one of Weber's three f
functions.
If flag = 0
, returns
f(x) = exp (iPi/24).eta((x+1)/2)/eta(x) such that j = (f^{24}16)^3/f^{24},
where j
is the elliptic j
invariant (see the function ellj
).
If flag = 1
, returns
f_1(x) = eta(x/2)/eta(x) such that j = (f_1^{24}+16)^3/f_1^{24}.
Finally, if flag = 2
, returns
f_2(x) = sqrt {2}eta(2x)/eta(x) such that j = (f_2^{24}+16)^3/f_2^{24}.
Note the identities f^8 = f_1^8+f_2^8
and ff_1f_2 = sqrt 2
.
The library syntax is weber0(x,flag,prec)
, or
wf(x,prec)
, wf1(x,prec)
or
wf2(x,prec)
.
(s)
Riemann's zeta function
zeta(s) = sum_{n >= 1}n^{s}
, computed using the EulerMaclaurin
summation formula, except when s
is of type integer, in which case it
is computed using Bernoulli numbers for
s <= 0
or s > 0
and even, and using modular forms for s > 0
and odd.
The library syntax is gzeta(s,prec)
.
These functions are by definition functions whose natural domain of
definition is either Z (or Z_{ > 0}
), or sometimes polynomials
over a base ring. Functions which concern polynomials exclusively will be
explained in the next section. The way these functions are used is
completely different from transcendental functions: in general only the types
integer and polynomial are accepted as arguments. If a vector or matrix type
is given, the function will be applied on each coefficient independently.
In the present version 2.2.0, all arithmetic functions in the narrow sense
of the word  Euler's totient function, the
Moebius function, the sums over divisors or powers of divisors
etc. call, after trial division by small primes, the same versatile
factoring machinery described under factorint
. It includes
Shanks SQUFOF, Pollard Rho, ECM and MPQS stages, and
has an early exit option for the functions moebius and (the integer
function underlying) issquarefree. Note that it relies on a (fairly
strong) probabilistic primality test: numbers found to be strong
pseudoprimes after 10 successful trials of the RabinMiller test are
declared primes.
({x = []})
adds the primes contained in the vector
x
(or the single integer x
) to the table computed upon GP initialization
(by pari_init
in library mode), and returns a row vector whose first
entries contain all primes added by the user and whose last entries have been
filled up with 1's. In total the returned row vector has 100 components.
Whenever factor
or smallfact
is subsequently called, first the
primes in the table computed by pari_init
will be checked, and then
the additional primes in this table. If x
is empty or omitted, just returns
the current list of extra primes.
The entries in x
are not checked for primality. They need only be positive
integers not divisible by any of the precomputed primes. It's in fact a nice
trick to add composite numbers, which for example the function
factor(x,0)
was not able to factor. In case the message ``impossible
inverse modulo <
some integermod>
'' shows up afterwards,
you have just stumbled over a nontrivial factor. Note that the arithmetic
functions in the narrow sense, like eulerphi, do not use this
extra table.
The present PARI version 2.2.0 allows up to 100 userspecified
primes to be appended to the table. This limit may be changed
by altering NUMPRTBELT
in file init.c
. To remove primes from the
list use removeprimes
.
The library syntax is addprimes(x)
.
(x,k)
if x belongs to R
, finds the best rational
approximation to x
with denominator at most equal to k
using continued
fractions.
The library syntax is bestappr(x,k)
.
(x,y)
finds u
and v
minimal in a
natural sense such that x*u+y*v = gcd(x,y)
. The arguments
must be both integers or both polynomials, and the result is a
row vector with three components u
, v
, and gcd(x,y)
.
The library syntax is vecbezout(x,y)
to get the vector, or gbezout(x,y, &u, &v)
which gives as result the address of the created gcd, and puts
the addresses of the corresponding created objects into u
and v
.
(x,y)
as bezout
, with the resultant of x
and
y
replacing the gcd.
The library syntax is vecbezoutres(x,y)
to get the vector, or subresext(x,y, &u,
&v)
which gives as result the address of the created gcd, and puts the
addresses of the corresponding created objects into u
and v
.
(x)
number of prime divisors of x
counted with
multiplicity. x
must be an integer.
The library syntax is bigomega(x)
, the result is a long
.
(x,y)
binomial coefficient \binom x y
.
Here y
must be an integer, but x
can be any PARI object.
The library syntax is binome(x,y)
, where y
must be a long
.
(x,y)
if x
and y
are both integermods or both
polmods, creates (with the same type) a z
in the same residue class
as x
and in the same residue class as y
, if it is possible.
This function also allows vector and matrix arguments, in which case the
operation is recursively applied to each component of the vector or matrix.
For polynomial arguments, it is applied to each coefficient. Finally
chinese(x,x) = x
regardless of the type of x
; this allows vector
arguments to contain other data, so long as they are identical in both
vectors.
The library syntax is chinois(x,y)
.
(x)
computes the gcd of all the coefficients of x
,
when this gcd makes sense. If x
is a scalar, this simply returns x
. If x
is a polynomial (and by extension a power series), it gives the usual content
of x
. If x
is a rational function, it gives the ratio of the contents of
the numerator and the denominator. Finally, if x
is a vector or a matrix,
it gives the gcd of all the entries.
The library syntax is content(x)
.
(x,{b},{lmax})
creates the row vector whose
components are the partial quotients of the continued fraction
expansion of x
, the number of partial quotients being limited to lmax
.
If x
is a real number, the expansion stops at the last significant partial
quotient if lmax
is omitted. x
can also be a rational function or a power
series.
If a vector b
is supplied, the numerators will be equal to the coefficients
of b
. The length of the result is then equal to the length of b
, unless a
partial remainder is encountered which is equal to zero. In which case the
expansion stops. In the case of real numbers, the stopping criterion is thus
different from the one mentioned above since, if b
is too long, some partial
quotients may not be significant.
If b
is an integer, the command is understood as contfrac(x,lmax)
.
The library syntax is contfrac0(x,b,lmax)
. Also available are
gboundcf(x,lmax)
, gcf(x)
, or gcf2(b,x)
, where lmax
is a C integer.
(x)
when x
is a vector or a onerow matrix, x
is considered as the list of partial quotients [a_0,a_1,...,a_n]
of a
rational number, and the result is the 2 by 2 matrix
[p_n,p_{n1};q_n,q_{n1}]
in the standard notation of continued fractions,
so p_n/q_n = a_0+1/(a_1+...+1/a_n)...)
. If x
is a matrix with two rows
[b_0,b_1,...,b_n]
and [a_0,a_1,...,a_n]
, this is then considered as a
generalized continued fraction and we have similarly
p_n/q_n = 1/b_0(a_0+b_1/(a_1+...+b_n/a_n)...)
. Note that in this case one
usually has b_0 = 1
.
The library syntax is pnqn(x)
.
(n,{flag = 0})
if n
is a nonzero integer written as
n = df^2
with d
squarefree, returns d
. If flag
is nonzero,
returns the twoelement row vector [d,f]
.
The library syntax is core0(n,flag)
.
Also available are
core(n)
( = core(n,0)
) and
core2(n)
( = core(n,1)
).
(n,{flag})
if n
is a nonzero integer written as
n = df^2
with d
fundamental discriminant (including 1), returns d
. If
flag
is nonzero, returns the twoelement row vector [d,f]
. Note that if
n
is not congruent to 0 or 1 modulo 4, f
will be a half integer and not
an integer.
The library syntax is coredisc0(n,flag)
.
Also available are
coredisc(n)
( = coredisc(n,0)
) and
coredisc2(n)
( = coredisc(n,1)
).
(x,y)
x
and y
being vectors of perhaps different
lengths but with y[1] ! = 0
considered as Dirichlet series, computes
the quotient of x
by y
, again as a vector.
The library syntax is dirdiv(x,y)
.
(p = a,b,expr,{c})
computes the
Dirichlet series to b
terms of the Euler product of
expression expr as p
ranges through the primes from a
to b
.
expr must be a polynomial or rational function in another variable
than p
(say X
) and expr(X)
is understood as the Dirichlet
series (or more precisely the local factor) expr(p^{s})
. If c
is
present, output only the first c
coefficients in the series.
The library syntax is direuler(entree *ep, GEN a, GEN b, char *expr)
(x,y)
x
and y
being vectors of perhaps different
lengths considered as Dirichlet series, computes the product of
x
by y
, again as a vector.
The library syntax is dirmul(x,y)
.
(x)
creates a row vector whose components are the
positive divisors of the integer x
in increasing order. The factorization
of x
(as output by factor
) can be used instead.
The library syntax is divisors(x)
.
(x)
Euler's phi
(totient) function of x
, in other words
(Z/xZ)^*
. x
must be of type integer.
The library syntax is phi(x)
.
(x,{lim = 1})
general factorization function.
If x
is of type integer, rational, polynomial or rational function, the
result is a twocolumn matrix, the first column being the irreducibles
dividing x
(prime numbers or polynomials), and the second the exponents.
If x
is a vector or a matrix, the factoring is done componentwise (hence
the result is a vector or matrix of twocolumn matrices). By definition,
0
is factored as 0^1
.
If x
is of type integer or rational, an argument lim can be
added, meaning that we look only for factors up to lim, or to
primelimit
, whichever is lowest (except when lim = 0
where the
effect is identical to setting lim = primelimit
). Hence in this
case, the remaining part is not necessarily prime. See factorint for
more information about the algorithms used.
The polynomials or rational functions to be factored must have scalar coefficients. In particular PARI does not know how to factor multivariate polynomials.
Note that PARI tries to guess in a sensible way over which ring you want to factor. Note also that factorization of polynomials is done up to multiplication by a constant. In particular, the factors of rational polynomials will have integer coefficients, and the content of a polynomial or rational function is discarded and not included in the factorization. If you need it, you can always ask for the content explicitly:
? factor(t^2 + 5/2*t + 1) %1 = [2*t + 1 1]
[t + 2 1]
? content(t^2 + 5/2*t + 1) %2 = 1/2
See also factornf.
The library syntax is factor0(x,lim)
, where lim is a C integer.
Also available are
factor(x)
( = factor0(x,1)
),
smallfact(x)
( = factor0(x,0)
).
(f,{nf})
f
being any factorization, gives back
the factored object. If a second argument nf
is supplied, f
is
assumed to be a prime ideal factorization in the number field nf
.
The resulting ideal is given in HNF form.
The library syntax is factorback(f,nf)
, where an omitted
nf
is entered as NULL
.
(x,p)
factors the polynomial x
modulo the
prime p
, using distinct degree plus
CantorZassenhaus. The coefficients of x
must be
operationcompatible with Z/pZ
. The result is a twocolumn matrix, the
first column being the irreducible polynomials dividing x
, and the second
the exponents. If you want only the degrees of the irreducible
polynomials (for example for computing an L
function), use
factormod(x,p,1)
. Note that the factormod
algorithm is
usually faster than factorcantor
.
The library syntax is factcantor(x,p)
.
(x,p,a)
factors the polynomial x
in the field
F_q
defined by the irreducible polynomial a
over F_p
. The
coefficients of x
must be operationcompatible with Z/pZ
. The result
is a twocolumn matrix, the first column being the irreducible polynomials
dividing x
, and the second the exponents. It is recommended to use for
the variable of a
(which will be used as variable of a polmod) a name
distinct from the other variables used, so that a lift()
of the
result will be legible. If all the coefficients of x
are in F_p
, a much faster algorithm is applied, using the computation of isomorphisms between finite fields.
The library syntax is factmod9(x,p,a)
.
(x)
or x!
factorial of x
. The expression x!
gives a result which is an integer, while factorial(x)
gives a real
number.
The library syntax is mpfact(x)
for x!
and
mpfactr(x,prec)
for factorial(x)
. x
must be a long
integer and not a PARI integer.
(n,{flag = 0})
factors the integer n using a
combination of the Shanks SQUFOF and Pollard Rho method (with
modifications due to Brent), Lenstra's ECM (with modifications by
Montgomery), and MPQS (the latter adapted from the LiDIA code
with the kind permission of the LiDIA maintainers), as well as a search for
pure powers with exponents <= 10
. The output is a twocolumn matrix as for
factor
.
This gives direct access to the integer factoring engine called by most arithmetical functions. flag is optional; its binary digits mean 1: avoid MPQS, 2: skip first stage ECM (we may still fall back to it later), 4: avoid Rho and SQUFOF, 8: don't run final ECM (as a result, a huge composite may be declared to be prime). Note that a (strong) probabilistic primality test is used; thus composites might (very rarely) not be detected.
The machinery underlying this function is still in a somewhat experimental
state, but should be much faster on average than pure ECM as used by all
PARI versions up to 2.0.8, at the expense of heavier memory use. You are
invited to play with the flag settings and watch the internals at work by
using GP's debuglevel
default parameter (level 3 shows just the
outline, 4 turns on time keeping, 5 and above show an increasing amount
of internal details). If you see anything funny happening, please let
us know.
The library syntax is factorint(n,flag)
.
(x,p,{flag = 0})
factors the polynomial x
modulo
the prime integer p
, using Berlekamp. The coefficients of x
must be
operationcompatible with Z/pZ
. The result is a twocolumn matrix, the
first column being the irreducible polynomials dividing x
, and the second
the exponents. If flag
is nonzero, outputs only the degrees of the
irreducible polynomials (for example, for computing an L
function). A
different algorithm for computing the mod p
factorization is
factorcantor
which is sometimes faster.
The library syntax is factormod(x,p,flag)
. Also available are
factmod(x,p)
(which is equivalent to factormod(x,p,0)
) and
simplefactmod(x,p)
( = factormod(x,p,1)
).
(x)
x^{th}
Fibonacci number.
The library syntax is fibo(x)
. x
must be a long
.
(p,n,{v = x})
computes a monic polynomial of degree
n
which is irreducible over F_p
. For instance if
P = ffinit(3,2,y)
, you can represent elements in F_{3^2}
as polmods
modulo P
.
The library syntax is ffinit(p,n,v)
, where v
is a variable number.
(x,y,{flag = 0})
creates the greatest common divisor of x
and y
. x
and y
can be of quite general types, for instance both
rational numbers. Vector/matrix types are also accepted, in which case
the GCD is taken recursively on each component. Note that for these
types, gcd
is not commutative.
If flag = 0
, use Euclid's algorithm.
If flag = 1
, use the modular gcd algorithm (x
and y
have to be
polynomials, with integer coefficients).
If flag = 2
, use the subresultant algorithm.
The library syntax is gcd0(x,y,flag)
. Also available are
ggcd(x,y)
, modulargcd(x,y)
, and srgcd(x,y)
corresponding to flag = 0
, 1
and 2
respectively.
(x,y,{p})
Hilbert symbol of x
and y
modulo
p
. If x
and y
are of type integer or fraction, an explicit third
parameter p
must be supplied, p = 0
meaning the place at infinity.
Otherwise, p
needs not be given, and x
and y
can be of compatible types
integer, fraction, real, integermod a prime (result is undefined if the
modulus is not prime), or p
adic.
The library syntax is hil(x,y,p)
.
(x)
true (1) if x
is equal to 1 or to the
discriminant of a quadratic field, false (0) otherwise.
The library syntax is gisfundamental(x)
, but the
simpler function isfundamental(x)
which returns a long
should be used if x
is known to be of type integer.
(x,{flag = 0})
if flag = 0
(default), true (1) if x
is a strong pseudoprime
for 10 randomly chosen bases, false (0) otherwise.
If flag = 1
, use PocklingtonLehmer ``P1'' test. true (1) if x
is
prime, false (0) otherwise.
If flag = 2
, use PocklingtonLehmer ``P1'' test and output a primality
certificate as follows: return 0 if x
is composite, 1 if x
is a
small prime (currently strictly less than 341 550 071 728 321
), and
a matrix if x
is a large prime. The matrix has three columns. The
first contains the prime factors p
, the second the corresponding
elements a_p
as in Proposition 8.3.1 in GTM 138, and the third the
output of isprime(p,2).
In the two last cases, the algorithm fails if one of the (strong pseudo)prime factors is not prime, but it should be exceedingly rare.
The library syntax is gisprime(x,flag)
, but the simpler function isprime(x)
which returns a long
should be used if x
is known to be of
type integer. Also available is plisprime(N,flag)
,
corresponding to gisprime(x,flag+1)
if x
is known to be of
type integer.
(x)
true (1) if x
is a strong
pseudoprime for a randomly chosen base, false (0) otherwise.
The library syntax is gispsp(x)
, but the
simpler function ispsp(x)
which returns a long
should be used if x
is known to be of type integer.
(x,{&n})
true (1) if x
is square, false (0) if
not. x
can be of any type. If n
is given and an exact square root had to
be computed in the checking process, puts that square root in n
. This is in
particular the case when x
is an integer or a polynomial. This is not
the case for intmods (use quadratic reciprocity) or series (only check the
leading coefficient).
The library syntax is gcarrecomplet(x,&n)
. Also available is gcarreparfait(x)
.
(x)
true (1) if x
is squarefree, false (0) if not.
Here x
can be an integer or a polynomial.
The library syntax is gissquarefree(x)
, but the simpler function issquarefree(x)
which returns a long
should be used if x
is known to be of type
integer. This issquarefree is just the square of the
Moebius function, and is computed as a multiplicative
arithmetic function much like the latter.
(x,y)
Kronecker
(i.e. generalized Legendre) symbol ((x)/(y))
. x
and y
must be of type integer.
The library syntax is kronecker(x,y)
, the result (0
or + 1
) is a long
.
(x,y)
least common multiple of x
and y
, i.e. such
that lcm(x,y)*gcd(x,y) = abs(x*y)
.
The library syntax is glcm(x,y)
.
(x)
Moebius mu
function of x
. x
must
be of type integer.
The library syntax is mu(x)
, the result (0
or + 1
) is a long
.
(x)
finds the smallest prime greater than or
equal to x
. x
can be of any real type. Note that if x
is a prime,
this function returns x
and not the smallest prime strictly larger than x
.
The library syntax is nextprime(x)
.
(x)
number of divisors of x
. x
must be of type
integer, and the result is a long
.
The library syntax is numbdiv(x)
.
(x)
number of distinct prime divisors of x
. x
must be of type integer.
The library syntax is omega(x)
, the result is a long
.
(x)
finds the largest prime less than or equal to
x
. x
can be of any real type. Returns 0 if x <= 1
.
Note that if x
is a prime, this function returns x
and not the largest
prime strictly smaller than x
.
The library syntax is precprime(x)
.
(x)
the x^{th}
prime number, which must be among
the precalculated primes.
The library syntax is prime(x)
. x
must be a long
.
(x)
creates a row vector whose components
are the first x
prime numbers, which must be among the precalculated primes.
The library syntax is primes(x)
. x
must be a long
.
(x,{flag = 0})
class number of the quadratic field
of discriminant x
. In the present version 2.2.0, a simple algorithm is used
for x > 0
, so x
should not be too large (say x < 10^7
) for the time to be
reasonable. On the other hand, for x < 0
one can reasonably compute
classno(x
) for x < 10^{25}
, since the method used is Shanks' method
which is in O(x^{1/4})
. For larger values of D
, see
quadclassunit
.
If flag = 1
, compute the class number using Euler products and the
functional equation. However, it is in O(x^{1/2})
.
Important warning. For D < 0
, this function often gives
incorrect results when the class group is noncyclic, because the authors
were too lazy to implement Shanks' method completely. It is therefore
strongly recommended to use either the version with flag = 1
, the function
qfbhclassno(x)
if x
is known to be a fundamental discriminant, or
the function quadclassunit
.
The library syntax is qfbclassno0(x,flag)
. Also available are
classno(x)
( = qfbclassno(x)
),
classno2(x)
( = qfbclassno(x,1)
), and finally
there exists the function hclassno(x)
which computes the class
number of an imaginary quadratic field by counting reduced forms, an O(x)
algorithm. See also qfbhclassno
.
(x,y)
composition of the binary quadratic forms
x
and y
, without reduction of the result. This is useful e.g. to
compute a generating element of an ideal.
The library syntax is compraw(x,y)
.
(x)
Hurwitz class number of x
, where x
is
nonnegative and congruent to 0 or 3 modulo 4. See also qfbclassno
.
The library syntax is hclassno(x)
.
(x,y,l)
composition of the primitive positive
definite binary quadratic forms x
and y
using the NUCOMP and NUDUPL
algorithms of Shanks (à la Atkin). l
is any positive constant,
but for optimal speed, one should take l = D^{1/4}
, where D
is the common
discriminant of x
and y
. When x
and y
do not have the same
discriminant, the result is undefined.
The library syntax is nucomp(x,y,l)
. The auxiliary function
nudupl(x,l)
should be used instead for speed when x = y
.
(x,n)
n
th power of the primitive positive definite
binary quadratic form x
using the NUCOMP and NUDUPL algorithms (see
qfbnucomp
).
The library syntax is nupow(x,n)
.
(x,n)
n
th power of the binary quadratic form
x
, computed without doing any reduction (i.e. using qfbcompraw
).
Here n
must be nonnegative and n < 2^{31}
.
The library syntax is powraw(x,n)
where n
must be a long
integer.
(x,p)
prime binary quadratic form of discriminant
x
whose first coefficient is the prime number p
. By abuse of notation,
p = 1
is a valid special case which returns the unit form. Returns an
error if x
is not a quadratic residue mod p
. In the case where x > 0
,
the ``distance'' component of the form is set equal to zero according to
the current precision.
The library syntax is primeform(x,p,prec)
, where the third variable prec
is a
long
, but is only taken into account when x > 0
.
(x,{flag = 0},{D},{isqrtD},{sqrtD})
reduces the binary quadratic form x
(updating Shanks's distance function
if x
is indefinite). The binary digits of flag
are toggles meaning
1: perform a single reduction step
2: don't update Shanks's distance
D
, isqrtD, sqrtD, if present, supply the values of the
discriminant, \lfloor sqrt {D}\rfloor
, and sqrt {D}
respectively
(no checking is done of these facts). If D < 0
these values are useless,
and all references to Shanks's distance are irrelevant.
The library syntax is qfbred0(x,flag,D,isqrtD,sqrtD)
. Use NULL
to omit any of D
, isqrtD, sqrtD.
Also available are
redimag(x)
( = qfbred(x)
where x
is definite),
and for indefinite forms:
redreal(x)
( = qfbred(x)
),
rhoreal(x)
( = qfbred(x,1)
),
redrealnod(x,sq)
( = qfbred(x,2,,isqrtD)
),
rhorealnod(x,sq)
( = qfbred(x,3,,isqrtD)
).
(D,{flag = 0},{tech = []})
BuchmannMcCurley's subexponential algorithm for computing the class
group of a quadratic field of discriminant D
. If D
is not fundamental,
the function may or may not be defined, but usually is, and often gives the
right answer (a warning is issued). The more general function bnrinit
should be used to compute the class group of an order.
This function should be used instead of qfbclassno
or quadregula
when D < 10^{25}
, D > 10^{10}
, or when the structure is wanted.
If flag
is nonzero and D > 0
, computes the narrow class group and
regulator, instead of the ordinary (or wide) ones. In the current version
2.2.0, this doesn't work at all : use the general function bnfnarrow
.
Optional parameter tech is a row vector of the form
[c_1,c_2]
, where c_1
and c_2
are positive real numbers which
control the execution time and the stack size. To get maximum speed,
set c_2 = c
. To get a rigorous result (under GRH) you must take
c_2 = 6
. Reasonable values for c
are between 0.1
and 2
.
The result of this function is a vector v
with 4 components if D < 0
, and
5
otherwise. The correspond respectively to
*
v[1]
: the class number
*
v[2]
: a vector giving the structure of the class group as a
product of cyclic groups;
*
v[3]
: a vector giving generators of those cyclic groups (as
binary quadratic forms).
*
v[4]
: (omitted if D < 0
) the regulator, computed to an
accuracy which is the maximum of an internal accuracy determined by the
program and the current default (note that once the regulator is known to a
small accuracy it is trivial to compute it to very high accuracy, see the
tutorial).
*
v[5]
: a measure of the correctness of the result. If it is
close to 1, the result is correct (under GRH). If it is close to a
larger integer, this shows that the class number is off by a factor equal
to this integer, and you must start again with a larger value for c_1
or
a different random seed. In this case, a warning message is printed.
The library syntax is quadclassunit0(D,flag,tech)
. Also available are
buchimag(D,c_1,c_2)
and buchreal(D,flag,c_1,c_2)
.
(x)
discriminant of the quadratic field
Q( sqrt {x})
, where x belongs to Q
.
The library syntax is quaddisc(x)
.
(D,{flag = 0})
relative equation defining the
Hilbert class field of the quadratic field of discriminant D
.
If flag
is nonzero
and D < 0
, outputs [form,root(form)]
(to be used for
constructing subfields). If flag
is nonzero and D > 0
, try hard to
get the best modulus.
Uses complex multiplication in the imaginary case and Stark units
in the real case.
The library syntax is quadhilbert(D,flag,prec)
.
(x)
creates the quadratic number
omega = (a+ sqrt {x})/2
where a = 0
if x = 0 mod 4
,
a = 1
if x = 1 mod 4
, so that (1,omega)
is an integral basis for
the quadratic order of discriminant x
. x
must be an integer congruent to
0 or 1 modulo 4.
The library syntax is quadgen(x)
.
(D,{v = x})
creates the ``canonical'' quadratic
polynomial (in the variable v
) corresponding to the discriminant D
,
i.e. the minimal polynomial of quadgen(x)
. D
must be an integer
congruent to 0 or 1 modulo 4.
The library syntax is quadpoly0(x,v)
.
(D,f,{flag = 0})
relative equation for the ray class
field of conductor f
for the quadratic field of discriminant D
(which
can also be a bnf
), using analytic methods.
For D < 0
, uses the sigma
function. flag
has the following meaning: if
it's an odd integer, outputs instead the vector of [ideal,
I<corresponding root>]
. It can also be a twocomponent vector
[lambda,flag]
, where flag is as above and lambda
is the technical
element of bnf
necessary for Schertz's method. In that case, returns
0 if lambda
is not suitable.
For D > 0
, uses Stark's conjecture. If flag
is nonzero, try hard to
get the best modulus. The function may fail with the following message
"Cannot find a suitable modulus in FindModulus"
See bnrstark
for more details about the real case.
The library syntax is quadray(D,f,flag)
.
(x)
regulator of the quadratic field of
positive discriminant x
. Returns an error if x
is not a discriminant
(fundamental or not) or if x
is a square. See also quadclassunit
if
x
is large.
The library syntax is regula(x,prec)
.
(x)
fundamental unit of the
real quadratic field Q( sqrt x)
where x
is the positive discriminant
of the field. If x
is not a fundamental discriminant, this probably gives
the fundamental unit of the corresponding order. x
must be of type
integer, and the result is a quadratic number.
The library syntax is fundunit(x)
.
({x = []})
removes the primes listed in x
from
the prime number table. In particular removeprimes(addprimes)
empties
the extra prime table. x
can also be a single integer. List the current
extra primes if x
is omitted.
The library syntax is removeprimes(x)
.
(x,{k = 1})
sum of the k^{th}
powers of the
positive divisors of x
. x
must be of type integer.
The library syntax is sumdiv(x)
( = sigma(x)
) or gsumdivk(x,k)
( =
sigma(x,k)
), where k
is a C long integer.
(x)
integer square root of x
, which must be of PARI
type integer. The result is nonnegative and rounded towards zero. A
negative x
is allowed, and the result in that case is I*sqrtint(x)
.
The library syntax is racine(x)
.
(x,g)
g
must be a primitive root mod a prime p
, and
the result is the discrete log of x
in the multiplicative group
(Z/pZ)^*
. This function using a simpleminded babystep/giantstep
approach and requires O( sqrt {p})
storage, hence it cannot be used for
p
greater than about 10^{13}
.
The library syntax is znlog(x,g)
.
(x)
x
must be an integer mod n
, and the result is the
order of x
in the multiplicative group (Z/nZ)^*
. Returns an error if x
is not invertible.
The library syntax is order(x)
.
(x)
returns a primitive root of x
, where x
is a prime power.
The library syntax is gener(x)
.
(n)
gives the structure of the multiplicative group
(Z/nZ)^*
as a 3component row vector v
, where v[1] = phi(n)
is the
order of that group, v[2]
is a k
component rowvector d
of integers
d[i]
such that d[i] > 1
and d[i]  d[i1]
for i >= 2
and
(Z/nZ)^* ~ prod_{i = 1}^k(Z/d[i]Z)
, and v[3]
is a k
component row
vector giving generators of the image of the cyclic groups Z/d[i]Z
.
The library syntax is znstar(n)
.
We have implemented a number of functions which are useful for number theorists working on elliptic curves. We always use Tate's notations. The functions assume that the curve is given by a general Weierstrass model
y^2+a_1xy+a_3y = x^3+a_2x^2+a_4x+a_6,
where a priori the a_i
can be of any scalar type. This curve can be
considered as a fivecomponent vector E = [a1,a2,a3,a4,a6]
. Points on
E
are represented as twocomponent vectors [x,y]
, except for the
point at infinity, i.e. the identity element of the group law, represented by
the onecomponent vector [0]
.
It is useful to have at one's disposal more information. This is given by
the function ellinit
(see there), which usually gives a 19 component
vector (which we will call a long vector in this section). If a specific flag
is added, a vector with only 13 component will be output (which we will call
a medium vector). A medium vector just gives the first 13 components of the
long vector corresponding to the same curve, but is of course faster to
compute. The following member functions are available to deal with the
output of ellinit
:
a1
a6
, b2
b8
, c4
c6
:
coefficients of the elliptic curve.
area
: volume of the complex lattice defining E
.
disc
: discriminant of the curve.
j
: j
invariant of the curve.
omega
: [omega_1,omega_2]
, periods forming a basis of
the complex lattice defining E
(omega_1
is the
real period, and omega_2/omega_1
belongs to
Poincaré's halfplane).
eta
: quasiperiods [eta_1, eta_2]
, such that
eta_1omega_2eta_2omega_1 = iPi
.
roots
: roots of the associated Weierstrass equation.
tate
: [u^2,u,v]
in the notation of Tate.
w
: Mestre's w
(this is technical).
Their use is best described by an example: assume that E
was output by
ellinit
, then typing E.disc
will retrieve the curve's
discriminant. The member functions area
, eta
and omega
are
only available for curves over Q. Conversely, tate
and w
are
only available for curves defined over Q_p
.
Some functions, in particular those relative to height computations (see
ellheight
) require also that the curve be in minimal Weierstrass
form. This is achieved by the function ellglobalred
.
All functions related to elliptic curves share the prefix ell
, and the
precise curve we are interested in is always the first argument, in either
one of the three formats discussed above, unless otherwise specified. For
instance, in functions which do not use the extra information given by long
vectors, the curve can be given either as a fivecomponent vector, or by one
of the longer vectors computed by ellinit
.
(E,z1,z2)
sum of the points z1
and z2
on the
elliptic curve corresponding to the vector E
.
The library syntax is addell(E,z1,z2)
.
(E,n)
computes the coefficient a_n
of the
L
function of the elliptic curve E
, i.e. in principle coefficients of a
newform of weight 2 assuming TaniyamaWeil conjecture (which is now
known to hold in full generality thanks to the work of Breuil,
Conrad, Diamond, Taylor and Wiles). E
must be a
medium or long vector of the type given by ellinit
. For this function
to work for every n
and not just those prime to the conductor, E
must
be a minimal Weierstrass equation. If this is not the case, use the
function ellglobalred
first before using ellak
.
The library syntax is akell(E,n)
.
(E,n)
computes the vector of the first n
a_k
corresponding to the elliptic curve E
. All comments in ellak
description remain valid.
The library syntax is anell(E,n)
, where n
is a C integer.
(E,p,{flag = 0})
computes the a_p
corresponding to the
elliptic curve E
and the prime number p
. These are defined by the
equation #E(F_p) = p+1  a_p
, where #E(F_p)
stands for the number
of points of the curve E
over the finite field F_p
. When flag
is 0
,
this uses the babystep giantstep method and a trick due to Mestre. This
runs in time O(p^{1/4})
and requires O(p^{1/4})
storage, hence becomes
unreasonable when p
has about 30 digits.
If flag
is 1
, computes the a_p
as a sum of Legendre symbols. This is
slower than the previous method as soon as p
is greater than 100, say.
No checking is done that p
is indeed prime. E
must be a medium or long
vector of the type given by ellinit
, defined over Q, F_p
or
Q_p
. E
must be given by a Weierstrass equation minimal at p
.
The library syntax is ellap0(E,p,flag)
. Also available are apell(E,p)
, corresponding
to flag = 0
, and apell2(E,p)
(flag = 1
).
(E,z1,z2)
if z1
and z2
are points on the elliptic
curve E
, this function computes the value of the canonical bilinear form on
z1
, z2
:
ellheight(E,z1+z2)  ellheight(E,z1)  ellheight(E,z2)
where +
denotes of course addition on E
. In addition, z1
or z2
(but not both) can be vectors or matrices. Note that this is equal to twice
some normalizations. E
is assumed to be integral, given by a minimal model.
The library syntax is bilhell(E,z1,z2,prec)
.
(E,v)
changes the data for the elliptic curve E
by changing the coordinates using the vector v = [u,r,s,t]
, i.e. if x'
and y'
are the new coordinates, then x = u^2x'+r
, y = u^3y'+su^2x'+t
.
The vector E
must be a medium or long vector of the type given by
ellinit
.
The library syntax is coordch(E,v)
.
(x,v)
changes the coordinates of the point or
vector of points x
using the vector v = [u,r,s,t]
, i.e. if x'
and
y'
are the new coordinates, then x = u^2x'+r
, y = u^3y'+su^2x'+t
(see also
ellchangecurve
).
The library syntax is pointch(x,v)
.
(E,k,{flag = 0})
E
being an elliptic curve as
output by ellinit
(or, alternatively, given by a 2component vector
[omega_1,omega_2]
), and k
being an even positive integer, computes
the numerical value of the Eisenstein series of weight k
at E
. When
flag is nonzero and k = 4
or 6, returns g_2
or g_3
with the correct
normalization.
The library syntax is elleisnum(E,k,flag)
.
(om)
returns the twocomponent row vector
[eta_1,eta_2]
of quasiperiods associated to om = [omega_1,
F<omega>_2]
The library syntax is elleta(om, prec)
(E)
calculates the arithmetic conductor, the global
minimal model of E
and the global Tamagawa number c
. Here E
is an
elliptic curve given by a medium or long vector of the type given by
ellinit
, and is supposed to have all its coefficients a_i
in
Q. The result is a 3 component vector [N,v,c]
. N
is the arithmetic
conductor of the curve, v
is itself a vector [u,r,s,t]
with rational
components. It gives a coordinate change for E
over Q such that the
resulting model has integral coefficients, is everywhere minimal, a_1
is 0
or 1, a_2
is 0, 1 or 1
and a_3
is 0 or 1. Such a model is unique, and
the vector v
is unique if we specify that u
is positive. To get the new
model, simply type ellchangecurve(E,v)
. Finally c
is the product of
the local Tamagawa numbers c_p
, a quantity which enters in the
Birch and SwinnertonDyer conjecture.
The library syntax is globalreduction(E)
.
(E,z,{flag = 0})
global ronTate height>NéronTate height of
the point z
on the elliptic curve E
. The vector E
must be a long vector
of the type given by ellinit
, with flag = 1
. If flag = 0
, this
computation is done using sigma and thetafunctions and a trick due to J.
Silverman. If flag = 1
, use Tate's 4^n
algorithm, which is much slower.
E
is assumed to be integral, given by a minimal model.
The library syntax is ellheight0(E,z,flag,prec)
. The Archimedean
contribution alone is given by the library function
hell(E,z,prec)
.
Also available are ghell(E,z,prec)
(flag = 0
) and
ghell2(E,z,prec)
(flag = 1
).
(E,x)
x
being a vector of points, this
function outputs the Gram matrix of x
with respect to the NéronTate
height, in other words, the (i,j)
component of the matrix is equal to
ellbil(E,x[i],x[j])
. The rank of this matrix, at least in some
approximate sense, gives the rank of the set of points, and if x
is a
basis of the MordellWeil group of E
, its determinant is equal to
the regulator of E
. Note that this matrix should be divided by 2 to be in
accordance with certain normalizations. E
is assumed to be integral,
given by a minimal model.
The library syntax is mathell(E,x,prec)
.
(E,{flag = 0})
computes some fixed data concerning the
elliptic curve given by the fivecomponent vector E
, which will be
essential for most further computations on the curve. The result is a
19component vector E (called a long vector in this section), shortened
to 13 components (medium vector) if flag = 1
. Both contain the
following information in the first 13 components:
a_1,a_2,a_3,a_4,a_6,b_2,b_4,b_6,b_8,c_4,c_6,Delta,j.
In particular, the discriminant is E[12]
(or E.disc
), and the
j
invariant is E[13]
(or E.j
).
The other six components are only present if flag
is 0
(or omitted!).
Their content depends on whether the curve is defined over R or not:
*
When E
is defined over R, E[14]
(E.roots
) is a
vector whose three components contain the roots of the associated Weierstrass
equation. If the roots are all real, then they are ordered by decreasing
value. If only one is real, it is the first component of E[14]
.
E[15]
(E.omega[1]
) is the real period of E
(integral of
dx/(2y+a_1x+a_3)
over the connected component of the identity element of
the real points of the curve), and E[16]
(E.omega[2]
) is a complex
period. In other words, omega_1 = E[15]
and omega_2 = E[16]
form a basis of
the complex lattice defining E
(E.omega
), with
tau = (omega_2)/(omega_1)
having positive imaginary part.
E[17]
and E[18]
are the corresponding values eta_1
and eta_2
such
that eta_1omega_2eta_2omega_1 = iPi
, and both can be retrieved by
typing E.eta
(as a row vector whose components are the eta_i
).
Finally, E[19]
(E.area
) is the volume of the complex lattice defining
E
.
*
When E
is defined over Q_p
, the p
adic valuation of j
must be negative. Then E[14]
(E.roots
) is the vector with a single
component equal to the p
adic root of the associated Weierstrass equation
corresponding to 1
under the Tate parametrization.
E[15]
is equal to the square of the u
value, in the notation of Tate.
E[16]
is the u
value itself, if it belongs to Q_p
, otherwise zero.
E[17]
is the value of Tate's q
for the curve E
.
E.tate
will yield the threecomponent vector [u^2,u,q]
.
E[18]
(E.w
) is the value of Mestre's w
(this is technical), and
E[19]
is arbitrarily set equal to zero.
For all other base fields or rings, the last six components are arbitrarily set equal to zero (see also the description of member functions related to elliptic curves at the beginning of this section).
The library syntax is ellinit0(E,flag,prec)
. Also available are
initell(E,prec)
(flag = 0
) and
smallinitell(E,prec)
(flag = 1
).
(E,z)
gives 1 (i.e. true) if the point z
is on
the elliptic curve E
, 0 otherwise. If E
or z
have imprecise coefficients,
an attempt is made to take this into account, i.e. an imprecise equality is
checked, not a precise one.
The library syntax is oncurve(E,z)
, and the result is a long
.
(x)
elliptic j
invariant. x
must be a complex number
with positive imaginary part, or convertible into a power series or a
p
adic number with positive valuation.
The library syntax is jell(x,prec)
.
(E,p)
calculates the Kodaira type of the
local fiber of the elliptic curve E
at the prime p
.
E
must be given by a medium or
long vector of the type given by ellinit
, and is assumed to have all
its coefficients a_i
in Z. The result is a 4component vector
[f,kod,v,c]
. Here f
is the exponent of p
in the arithmetic conductor of
E
, and kod
is the Kodaira type which is coded as follows:
1 means good reduction (type I_0
), 2, 3 and 4 mean types II, III and IV
respectively, 4+nu
with nu > 0
means type I_nu
;
finally the opposite values 1
, 2
, etc. refer to the starred types
I_0^*
, II^*
, etc. The third component v
is itself a vector [u,r,s,t]
giving the coordinate changes done during the local reduction. Normally, this
has no use if u
is 1, that is, if the given equation was already minimal.
Finally, the last component c
is the local Tamagawa number c_p
.
The library syntax is localreduction(E,p)
.
(E,s,{A = 1})
E
being a medium or long vector
given by ellinit
, this computes the value of the Lseries of E
at
s
. It is assumed that E
is a minimal model over Z and that the curve
is a modular elliptic curve. The optional parameter A
is a cutoff point for
the integral, which must be chosen close to 1 for best speed. The result
must be independent of A
, so this allows some internal checking of the
function.
Note that if the conductor of the curve is large, say greater than 10^{12}
,
this function will take an unreasonable amount of time since it uses an
O(N^{1/2})
algorithm.
The library syntax is lseriesell(E,s,A,prec)
where prec
is a long
and an
omitted A
is coded as NULL
.
(E,z)
gives the order of the point z
on the elliptic
curve E
if it is a torsion point, zero otherwise. In the present version
2.2.0, this is implemented only for elliptic curves defined over Q.
The library syntax is orderell(E,z)
.
(E,x)
gives a 0, 1 or 2component vector containing
the y
coordinates of the points of the curve E
having x
as
x
coordinate.
The library syntax is ordell(E,x)
.
(E,z)
if E
is an elliptic curve with coefficients
in R, this computes a complex number t
(modulo the lattice defining
E
) corresponding to the point z
, i.e. such that, in the standard
Weierstrass model, wp (t) = z[1], wp '(t) = z[2]
. In other words, this is the
inverse function of ellztopoint
.
If E
has coefficients in Q_p
, then either Tate's u
is in Q_p
, in
which case the output is a p
adic number t
corresponding to the point z
under the Tate parametrization, or only its square is, in which case the
output is t+1/t
. E
must be a long vector output by ellinit
.
The library syntax is zell(E,z,prec)
.
(E,z,n)
computes n
times the point z
for the
group law on the elliptic curve E
. Here, n
can be in Z, or n
can be a complex quadratic integer if the curve E
has complex multiplication
by n
(if not, an error message is issued).
The library syntax is powell(E,z,n)
.
(E,{p = 1})
E
being a medium or long vector given
by ellinit
, this computes the local (if p ! = 1
) or global (if p = 1
)
root number of the Lseries of the elliptic curve E
. Note that the global
root number is the sign of the functional equation and conjecturally is the
parity of the rank of the MordellWeil group.
The equation for E
must have
coefficients in Q but need not be minimal.
The library syntax is ellrootno(E,p)
and the result (equal to +1
) is a long
.
(E,z,{flag = 0})
value of the Weierstrass sigma
function of the lattice associated to E
as given by ellinit
(alternatively, E
can be given as a lattice [omega_1,omega_2]
).
If flag = 1
, computes an (arbitrary) determination of log (sigma(z))
.
If flag = 2,3
, same using the product expansion instead of theta series.
The library syntax is ellsigma(E,z,flag)
(E,z1,z2)
difference of the points z1
and z2
on the
elliptic curve corresponding to the vector E
.
The library syntax is subell(E,z1,z2)
.
(E)
computes the modular parametrization of the
elliptic curve E
, where E
is given in the (long or medium) format output
by ellinit
, in the form of a twocomponent vector [u,v]
of power
series, given to the current default series precision. This vector is
characterized by the following two properties. First the point (x,y) = (u,v)
satisfies the equation of the elliptic curve. Second, the differential
du/(2v+a_1u+a_3)
is equal to f(z)dz
, a differential form on
H/Gamma_0(N)
where N
is the conductor of the curve. The variable used in
the power series for u
and v
is x
, which is implicitly understood to be
equal to exp (2iPi z)
. It is assumed that the curve is a strong
Weil curve, and the Manin constant is equal to 1. The equation of
the curve E
must be minimal (use ellglobalred
to get a minimal
equation).
The library syntax is taniyama(E)
, and the precision of the result is determined by the
global variable precdl
.
(E,{flag = 0})
if E
is an elliptic curve defined
over Q, outputs the torsion subgroup of E
as a 3component vector
[t,v1,v2]
, where t
is the order of the torsion group, v1
gives the structure of the torsion group as a product of cyclic groups
(sorted by decreasing order), and v2
gives generators for these cyclic
groups. E
must be a long vector as output by ellinit
.
? E = ellinit([0,0,0,1,0]); ? elltors(E) %1 = [4, [2, 2], [[0, 0], [1, 0]]]
Here, the torsion subgroup is isomorphic to Z/2Z x Z/2Z
, with
generators [0,0]
and [1,0]
.
If flag = 0
, use Doud's algorithm : bound torsion by computing #E(F_p)
for small primes of good reduction, then look for torsion points using
Weierstrass parametrization (and Mazur's classification).
If flag = 1
, use LutzNagell (much slower), E
is allowed to be a
medium vector.
The library syntax is elltors0(E,flag)
.
(E,{z = x},{flag = 0})
Computes the value at z
of the Weierstrass wp
function attached to the
elliptic curve E
as given by ellinit
(alternatively, E
can be
given as a lattice [omega_1,omega_2]
).
If z
is omitted or is a simple variable, computes the power series
expansion in z
(starting z^{2}+O(z^2)
). The number of terms to an
even power in the expansion is the default serieslength in GP, and the
second argument (C long integer) in library mode.
Optional flag is (for now) only taken into account when z
is numeric, and
means 0: compute only wp (z)
, 1: compute [ wp (z), wp '(z)]
.
The library syntax is ellwp0(E,z,flag,prec,precdl)
. Also available is
weipell(E,precdl)
for the power series (in
x = polx[0]
).
(E,z)
value of the Weierstrass zeta
function of the
lattice associated to E
as given by ellinit
(alternatively, E
can
be given as a lattice [omega_1,omega_2]
).
The library syntax is ellzeta(E,z)
.
(E,z)
E
being a long vector, computes the
coordinates [x,y]
on the curve E
corresponding to the complex number z
.
Hence this is the inverse function of ellpointtoz
. In other words, if
the curve is put in Weierstrass form, [x,y]
represents the
function>Weierstrass wp
function and its derivative.
If z
is in the lattice defining E
over
C, the result is the point at infinity [0]
.
The library syntax is pointell(E,z,prec)
.
In this section can be found functions which are used almost exclusively for working in general number fields. Other less specific functions can be found in the next section on polynomials. Functions related to quadratic number fields can be found in the section Label se:arithmetic (Arithmetic functions).
We shall use the following conventions:
*
nf
denotes a number field, i.e. a 9component vector
in the format output by nfinit
. This contains the basic arithmetic data
associated to the number field: signature, maximal order, discriminant, etc.
*
bnf
denotes a big number field, i.e. a 10component
vector in the format output by bnfinit
. This contains nf
and
the deeper invariants of the field: units, class groups, as well as a lot of
technical data necessary for some complex fonctions like bnfisprincipal
.
*
bnr
denotes a big ``ray number field'', i.e. some data
structure output by bnrinit
, even more complicated than bnf
,
corresponding to the ray class group structure of the field, for some
modulus.
*
rnf
denotes a relative number field (see below).
*
ideal
can mean any of the following:
 a Zbasis, in Hermite normal form
(HNF) or not. In this case x
is a square matrix.
 an idele, i.e. a 2component vector, the first being an
ideal given as a Zbasis, the second being a r_1+r_2
component row
vector giving the complex logarithmic Archimedean information.
 a Z_K
generating system for an ideal.
 a column vector x
expressing an element of the number field
on the integral basis, in which case the ideal is treated as being the
principal idele (or ideal) generated by x
.
 a prime ideal, i.e. a 5component vector in the format output by
idealprimedec
.
 a polmod x
, i.e. an algebraic integer, in which case the ideal
is treated as being the principal idele generated by x
.
 an integer or a rational number, also treated as a principal idele.
*
a {character} on the Abelian group
\bigoplus (Z/N_iZ) g_i
is given by a row vector chi = [a_1,...,a_n]
such that
chi(prod g_i^{n_i}) = exp(2iPisum a_i n_i / N_i)
.
Warnings:
1) An element in nf
can be expressed either as a polmod or as a
vector of components on the integral basis nf.zk
. It is absolutely
essential that all such vectors be column vectors.
2) When giving an ideal by a Z_K
generating system to a function expecting
an ideal, it must be ensured that the function understands that it is a
Z_K
generating system and not a Zgenerating system. When the number of
generators is strictly less than the degree of the field, there is no
ambiguity and the program assumes that one is giving a Z_K
generating set.
When the number of generators is greater than or equal to the degree of the
field, however, the program assumes on the contrary that you are giving a
Zgenerating set. If this is not the case, you must absolutely
change it into a Zgenerating set, the simplest manner being to use
idealhnf(nf,x)
.
Concerning relative extensions, some additional definitions are necessary.
*
A {relative matrix} will be a matrix whose entries are
elements of a (given) number field nf
, always expressed as column
vectors on the integral basis nf.zk
. Hence it is a matrix of
vectors.
*
An ideal list will be a row vector of (fractional)
ideals of the number field nf
.
*
A pseudomatrix will be a pair (A,I)
where A
is a
relative matrix and I
an ideal list whose length is the same as the number
of columns of A
. This pair will be represented by a 2component row vector.
*
The module generated by a pseudomatrix (A,I)
is
the sum sum_i{a}_jA_j
where the {a}_j
are the ideals of I
and A_j
is the j
th column of A
.
*
A pseudomatrix (A,I)
is a pseudobasis of the module
it generates if A
is a square matrix with nonzero determinant and all the
ideals of I
are nonzero. We say that it is in Hermite Normal
Form (HNF) if it is upper triangular and all the
elements of the diagonal are equal to 1.
*
The determinant of a pseudobasis (A,I)
is the ideal
equal to the product of the determinant of A
by all the ideals of I
. The
determinant of a pseudomatrix is the determinant of any pseudobasis of the
module it generates.
Finally, when defining a relative extension, the base field should be
defined by a variable having a lower priority (i.e. a higher number)
than the variable defining the extension. For example, under GP you can
use the variable name y
(or t
) to define the base field, and the
variable name x
to define the relative extension.
Now a last set of definitions concerning the way big ray number fields
(or bnr) are input, using class field theory.
These are defined by a triple
a1
, a2
, a3
, where the defining set [a1,a2,a3]
can have any of the
following forms: [bnr]
, [bnr,subgroup]
,
[bnf,module]
, [bnf,module,subgroup]
, where:
*
bnf
is as output by bnfclassunit
or bnfinit
,
where units are mandatory unless the ideal is trivial; bnr by
bnrclass
(with flag > 0
) or bnrinit
. This is the ground field.
*
module is either an ideal in any form (see above) or a
twocomponent row vector containing an ideal and an r_1
component row
vector of flags indicating which real Archimedean embeddings to take in the
module.
*
subgroup is the HNF matrix of a subgroup of the ray class group
of the ground field for the modulus module. This is input as a square
matrix expressing generators of a subgroup of the ray class group
bnr.clgp
on the given generators.
The corresponding bnr is then the subfield of the ray class field of the ground field for the given modulus, associated to the given subgroup.
All the functions which are specific to relative extensions, number fields,
big number fields, big number rays, share the prefix rnf
, nf
,
bnf
, bnr
respectively. They are meant to take as first argument a
number field of that precise type, respectively output by rnfinit
,
nfinit
, bnfinit
, and bnrinit
.
However, and even though it may not be specified in the descriptions of the
functions below, it is permissible, if the function expects a nf
, to
use a bnf
instead (which contains much more information). The program
will make the effort of converting to what it needs. On the other hand, if
the program requires a big number field, the program will not launch
bnfinit
for you, which can be a costly operation. Instead, it will give
you a specific error message.
The data types corresponding to the structures described above are rather complicated. Thus, as we already have seen it with elliptic curves, GP provides you with some ``member functions'' to retrieve the data you need from these structures (once they have been initialized of course). The relevant types of number fields are indicated between parentheses:
bnf
(bnr, bnf ) : big number field.
clgp
(bnr, bnf ) : classgroup. This one admits the
following three subclasses:
cyc
: cyclic decomposition
(SNF).
gen
:
generators.
no
: number of elements.
diff
(bnr, bnf, nf ) : the different ideal.
codiff
(bnr, bnf, nf ) : the codifferent
(inverse of the different in the ideal group).
disc
(bnr, bnf, nf ) : discriminant.
fu
(bnr, bnf, nf ) :
fundamental units.
futu
(bnr, bnf ) : [u,w]
, u
is a vector of
fundamental units, w
generates the torsion.
nf
(bnr, bnf, nf ) : number field.
reg
(bnr, bnf, ) : regulator.
roots
(bnr, bnf, nf ) : roots of the
polnomial generating the field.
sign
(bnr, bnf, nf ) : [r_1,r_2]
the
signature of the field. This means that the field has r_1
real
embeddings, 2r_2
complex ones.
t2
(bnr, bnf, nf ) : the T2 matrix (see
nfinit
).
tu
(bnr, bnf, ) : a generator for the torsion
units.
tufu
(bnr, bnf, ) : as futu
, but outputs
[w,u]
.
zk
(bnr, bnf, nf ) : integral basis, i.e. a
Zbasis of the maximal order.
zkst
(bnr ) : structure of (Z_K/m)^*
(can be
extracted also from an idealstar).
For instance, assume that bnf = bnfinit(pol)
, for some
polynomial. Then bnf.clgp
retrieves the class group, and
bnf.clgp.no
the class number. If we had set bnf =
nfinit(I<pol>)
, both would have output an error message. All these
functions are completely recursive, thus for instance
bnr.bnf.nf.zk
will yield the maximal order of bnr (which
you could get directly with a simple bnr.zk
of course).
The following functions, starting with buch
in library mode, and with
bnf
under GP, are implementations of the subexponential algorithms for
finding class and unit groups under GRH, due to HafnerMcCurley,
Buchmann and CohenDiazOlivier.
The general call to the functions concerning class groups of general number
fields (i.e. excluding quadclassunit
) involves a polynomial P
and a
technical vector
tech = [c,c2,nrel,borne,nrpid,minsfb],
where the parameters are to be understood as follows:
P
is the defining polynomial for the number field, which must be in
Z[X]
, irreducible and, preferably, monic. In fact, if you supply a
nonmonic polynomial at this point, GP will issue a warning, then
transform your polynomial so that it becomes monic. Instead of the
normal result, say res
, you then get a vector [res,Mod(a,Q)]
,
where Mod(a,Q) = Mod(X,P)
gives the change of variables.
The numbers c
and c2
are positive real numbers which control the
execution time and the stack size. To get maximum speed, set c2 = c
. To get a
rigorous result (under GRH) you must take c2 = 12
(or c2 = 6
in the
quadratic case, but then you should use the much faster function
quadclassunit
). Reasonable values for c
are between 0.1
and
2
. (The defaults are c = c2 = 0.3
).
nrel
is the number of initial extra relations requested in
computing the
relation matrix. Reasonable values are between 5 and 20. (The default is 5).
borne
is a multiplicative coefficient of the Minkowski bound which
controls
the search for small norm relations. If this parameter is set equal to 0, the
program does not search for small norm relations. Otherwise reasonable values
are between 0.5
and 2.0
. (The default is 1.0
).
nrpid
is the maximal number of small norm relations associated to each
ideal in the factor base. Irrelevant when borne = 0
. Otherwise,
reasonable values are between 4 and 20. (The default is 4).
minsfb
is the minimal number of elements in the ``subfactorbase''.
If the
program does not seem to succeed in finding a full rank matrix (which you can
see in GP by typing \g 2
), increase this number. Reasonable values
are between 2 and 5. (The default is 3).
Remarks.
Apart from the polynomial P
, you don't need to supply any of the technical
parameters (under the library you still need to send at least an empty
vector, cgetg(1,t_VEC)
). However, should you choose to set some of
them, they must be given in the requested order. For example, if you
want to specify a given value of nrel
, you must give some values as well
for c
and c2
, and provide a vector [c,c2,nrel]
.
Note also that you can use an nf
instead of P
, which avoids
recomputing the integral basis and analogous quantities.
(bnf)
bnf
being a big number field
as output by bnfinit
or bnfclassunit
, checks whether the result
is correct, i.e. whether it is possible to remove the assumption of the
Generalized Riemann Hypothesis. If it is correct, the answer is 1.
If not, the program may output some error message, but more probably will loop
indefinitely. In no occasion can the program give a wrong answer
(barring bugs of course): if the program answers 1, the answer is certified.
The library syntax is certifybuchall(bnf)
, and the result is a C long.
(P,{flag = 0},{tech = []})
Buchmann's
subexponential algorithm for computing the class group, the regulator and a
system of fundamental units of the general algebraic number field K
defined by the irreducible polynomial P
with integer coefficients.
The result of this function is a vector v
with 10 components (it is
not a bnf
, you need bnfinit
for that), which for ease of
presentation is in fact output as a one column matrix. First we describe the
default behaviour (flag = 0
):
v[1]
is equal to the polynomial P
. Note that for optimum performance,
P
should have gone through polred
or nfinit(x,2)
.
v[2]
is the 2component vector [r1,r2]
, where r1
and r2
are as usual
the number of real and half the number of complex embeddings of the number
field K
.
v[3]
is the 2component vector containing the field discriminant and the
index.
v[4]
is an integral basis in Hermite normal form.
v[5]
(v.clgp
) is a 3component vector containing the class number
(v.clgp.no
), the structure of the class group as a product of cyclic
groups of order n_i
(v.clgp.cyc
), and the corresponding generators
of the class group of respective orders n_i
(v.clgp.gen
).
v[6]
(v.reg
) is the regulator computed to an accuracy which is the
maximum of an internally determined accuracy and of the default.
v[7]
is a measure of the correctness of the result. If it is close to 1,
the results are correct (under GRH). If it is close to a larger integer,
this shows that the product of the class number by the regulator is off by a
factor equal to this integer, and you must start again with a larger value
for c
or a different random seed, i.e. use the function setrand
.
(Since the computation involves a random process, starting again with exactly
the same parameters may give the correct result.) In this case a warning
message is printed.
v[8]
(v.tu
) a vector with 2 components, the first being the number
w
of roots of unity in K
and the second a primitive w
th root of unity
expressed as a polynomial.
v[9]
(v.fu
) is a system of fundamental units also expressed as
polynomials.
v[10]
gives a measure of the correctness of the computations of the
fundamental units (not of the regulator), expressed as a number of bits. If
this number is greater than 20
, say, everything is OK. If v[10] <= 0
,
then we have lost all accuracy in computing the units (usually an error
message will be printed and the units not given). In the intermediate cases,
one must proceed with caution (for example by increasing the current
precision).
If flag = 1
, and the precision happens to be insufficient for obtaining the
fundamental units exactly, the internal precision is doubled and the
computation redone, until the exact results are obtained. The user should be
warned that this can take a very long time when the coefficients of the
fundamental units on the integral basis are very large, for example in the
case of large real quadratic fields. In that case, there are alternate
methods for representing algebraic numbers which are not implemented in PARI.
If flag = 2
, the fundamental units and roots of unity are not computed.
Hence the result has only 7 components, the first seven ones.
tech
is a technical vector (empty by default) containing c
, c2
,
nrel, borne, nbpid, minsfb, in this order (see
the beginning of the section or the keyword bnf
).
You can supply any number of these provided you give an actual value to
each of them (the ``empty arg'' trick won't work here). Careful use of these
parameters may speed up your computations considerably.
The library syntax is bnfclassunit0(P,flag,tech,prec)
.
(P,{tech = []})
as bnfclassunit
, but only
outputs v[5]
, i.e. the class group.
The library syntax is bnfclassgrouponly(P,tech,prec)
, where tech
is as described under bnfclassunit
.
(nf,m)
if m
is a module as output in the
first component of an extension given by bnrdisclist
, outputs the
true module.
The library syntax is decodemodule(nf,m)
.
(P,{flag = 0},{tech = []})
essentially identical
to bnfclassunit
except that the output contains a lot of technical data,
and should not be printed out explicitly in general. The result of
bnfinit
is used in programs such as bnfisprincipal
,
bnfisunit
or bnfnarrow
. The result is a 10component vector
bnf
.
*
The first 6 and last 2 components are technical and in
principle are not used by the casual user. However, for the sake of
completeness, their description is as follows. We use the notations explained
in the book by H. Cohen, A Course in Computational Algebraic Number
Theory, Graduate Texts in Maths 138, SpringerVerlag, 1993, Section
6.5, and subsection 6.5.5 in particular.
bnf[1]
contains the matrix W
, i.e. the matrix in Hermite normal
form giving relations for the class group on prime ideal generators
(p_i)_{1 <= i <= r}
.
bnf[2]
contains the matrix B
, i.e. the matrix containing the
expressions of the prime ideal factorbase in terms of the p_i
. It is an
r x c
matrix.
bnf[3]
contains the complex logarithmic embeddings of the system of
fundamental units which has been found. It is an (r_1+r_2) x (r_1+r_21)
matrix.
bnf[4]
contains the matrix M''_C
of Archimedean components of the
relations of the matrix (WB)
.
bnf[5]
contains the prime factor base, i.e. the list of prime
ideals used in finding the relations.
bnf[6]
contains the permutation of the prime factor base which was
necessary to reduce the relation matrix to the form explained in subsection
6.5.5 of GTM 138 (i.e. with a big c x c
identity matrix on the lower
right). Note that in the above mentioned book, the need to permute the rows
of the relation matrices which occur was not emphasized.
bnf[9]
is a 3element row vector used in bnfisprincipal
only
and obtained as follows. Let D = U W V
obtained by applying the
Smith normal form algorithm to the matrix W
( = bnf[1]
) and
let U_r
be the reduction of U
modulo D
. The first elements of the
factorbase are given (in terms of bnf.gen
) by the columns of U_r
,
with archimedian component g_a
; let also GD_a
be the archimedian
components of the generators of the (principal) ideals defined by the
bnf.gen[i]^bnf.cyc[i]
. Then bnf[9] = [U_r, g_a, GD_a]
.
Finally, bnf[10]
is by default unused and set equal to 0. This
field is used to store further information about the field as it becomes
available (which is rarely needed, hence would be too expensive to compute
during the initial bnfinit
call). For instance, the generators of the
principal ideals bnf.gen[i]^bnf.cyc[i]
(during a call to
bnrisprincipal
), or those corresponding to the relations in W
and
B
(when the bnf
internal precision needs to be increased).
*
The less technical components are as follows:
bnf[7]
or bnf.nf
is equal to the number field data
nf
as would be given by nfinit
.
bnf[8]
is a vector containing the last 6 components of
bnfclassunit[,1]
, i.e. the classgroup bnf.clgp
, the
regulator bnf.reg
, the general ``check'' number which should be
close to 1, the number of roots of unity and a generator bnf.tu
,
the fundamental units bnf.fu
, and finally the check on their
computation. If the precision becomes insufficient, GP outputs a warning
(fundamental units too large, not given
) and does not strive to
compute the units by default (flag = 0
).
When flag = 1
, GP insists on finding the fundamental units exactly, the
internal precision being doubled and the computation redone, until the exact
results are obtained. The user should be warned that this can take a very
long time when the coefficients of the fundamental units on the integral
basis are very large.
When flag = 2
, on the contrary, it is initially agreed that GP
will not compute units.
When flag = 3
, computes a very small version of bnfinit
, a ``small big
number field'' (or sbnf for short) which contains enough information
to recover the full bnf
vector very rapidly, but which is much
smaller and hence easy to store and print. It is supposed to be used in
conjunction with bnfmake
. The output is a 12 component vector v
, as
follows. Let bnf
be the result of a full bnfinit
, complete with
units. Then v[1]
is the polynomial P
, v[2]
is the number of real
embeddings r_1
, v[3]
is the field discriminant, v[4]
is the integral
basis, v[5]
is the list of roots as in the sixth component of nfinit
,
v[6]
is the matrix MD
of nfinit
giving a Zbasis of the
different, v[7]
is the matrix W = bnf[1]
, v[8]
is the
matrix matalpha = bnf[2]
, v[9]
is the prime ideal factor base
bnf[5]
coded in a compact way, and ordered according to the
permutation bnf[6]
, v[10]
is the 2component vector giving the
number of roots of unity and a generator, expressed on the integral basis,
v[11]
is the list of fundamental units, expressed on the integral basis,
v[12]
is a vector containing the algebraic numbers alpha corresponding to
the columns of the matrix matalpha
, expressed on the integral basis.
Note that all the components are exact (integral or rational), except for
the roots in v[5]
. In practice, this is the only component which a user
is allowed to modify, by recomputing the roots to a higher accuracy if
desired. Note also that the member functions will not work on
sbnf, you have to use bnfmake
explicitly first.
The library syntax is bnfinit0(P,flag,tech,prec)
.
(bnf,x)
computes a complete system of
solutions (modulo units of positive norm) of the absolute norm equation
Norm(a) = x
,
where a
is an integer in bnf
. If bnf
has not been certified,
the correctness of the result depends on the validity of GRH.
The library syntax is bnfisintnorm(bnf,x)
.
(bnf,x,{flag = 1})
tries to tell whether the
rational number x
is the norm of some element y in bnf
. Returns a
vector [a,b]
where x = Norm(a)*b
. Looks for a solution which is an S
unit,
with S
a certain set of prime ideals containing (among others) all primes
dividing x
. If bnf
is known to be Galois, set flag = 0
(in
this case,
x
is a norm iff b = 1
). If flag
is non zero the program adds to S
the
following prime ideals, depending on the sign of flag
. If flag > 0
, the
ideals of norm less than flag
. And if flag < 0
the ideals dividing flag
.
If you are willing to assume GRH, the answer is guaranteed
(i.e. x
is a norm iff b = 1
), if S
contains all primes less than
12 log (disc(Bnf))^2
,
where Bnf
is the Galois closure of bnf
.
The library syntax is bnfisnorm(bnf,x,flag,prec)
, where flag
and
prec
are long
s.
(bnf,sfu,x)
bnf
being output by
bnfinit
, sfu by bnfsunit
, gives the column vector of
exponents of x
on the fundamental S
units and the roots of unity.
If x
is not a unit, outputs an empty vector.
The library syntax is bnfissunit(bnf,sfu,x)
.
(bnf,x,{flag = 1})
bnf
being the
number field data output by bnfinit
, and x
being either a Zbasis
of an ideal in the number field (not necessarily in HNF) or a prime ideal in
the format output by the function idealprimedec
, this function tests
whether the ideal is principal or not. The result is more complete than a
simple true/false answer: it gives a row vector [v_1,v_2,check]
, where
v_1
is the vector of components c_i
of the class of the ideal x
in the
class group, expressed on the generators g_i
given by bnfinit
(specifically bnf.clgp.gen
which is the same as
bnf[8][1][3]
). The c_i
are chosen so that 0 <= c_i < n_i
where n_i
is the order of g_i
(the vector of n_i
being
bnf.clgp.cyc
, that is bnf[8][1][2]
).
v_2
gives on the integral basis the components of alpha
such that
x = alphaprod_ig_i^{c_i}
. In particular, x
is principal if and only if
v_1
is equal to the zero vector, and if this the case x = alphaZ_K
where
alpha
is given by v_2
. Note that if alpha
is too large to be given, a
warning message will be printed and v_2
will be set equal to the empty
vector.
Finally the third component check is analogous to the last component of
bnfclassunit
: it gives a check on the accuracy of the result, in bits.
check should be at least 10
, and preferably much more. In any case, the
result is checked for correctness.
If flag = 0
, outputs only v_1
, which is much easier to compute.
If flag = 2
, does as if flag
were 0
, but doubles the precision until a
result is obtained.
If flag = 3
, as in the default behaviour (flag = 1
), but doubles the precision
until a result is obtained.
The user is warned that these two last setting may induce very lengthy computations.
The library syntax is isprincipalall(bnf,x,flag)
.
(bnf,x)
bnf
being the number field data
output by
bnfinit
and x
being an algebraic number (type integer, rational or
polmod), this outputs the decomposition of x
on the fundamental units and
the roots of unity if x
is a unit, the empty vector otherwise. More
precisely, if u_1
,...,u_r
are the fundamental units, and zeta
is
the generator of the group of roots of unity (found by bnfclassunit
or
bnfinit
), the output is a vector [x_1,...,x_r,x_{r+1}]
such that
x = u_1^{x_1}...u_r^{x_r}.zeta^{x_{r+1}}
. The x_i
are integers for
i <= r
and is an integer modulo the order of zeta
for i = r+1
.
The library syntax is isunit(bnf,x)
.
(sbnf)
sbnf being a ``small bnf
''
as output by bnfinit
(x,3)
, computes the complete bnfinit
information. The result is not identical to what bnfinit
would
yield, but is functionally identical. The execution time is very small
compared to a complete bnfinit
. Note that if the default precision in
GP (or prec
in library mode) is greater than the precision of the
roots sbnf[5]
, these are recomputed so as to get a result with
greater accuracy.
Note that the member functions are not available for sbnf, you
have to use bnfmake
explicitly first.
The library syntax is makebigbnf(sbnf,prec)
, where prec
is a
C long integer.
(bnf)
bnf
being a big number field as
output by bnfinit
, computes the narrow class group of bnf
. The
output is a 3component row vector v
analogous to the corresponding
class group component bnf.clgp
(bnf[8][1]
): the
first component is the narrow class number v.no
, the second component
is a vector containing the SNF cyclic components
v.cyc
of the narrow
class group, and the third is a vector giving the generators of the
corresponding v.gen
cyclic groups. Note that this function is a
special case of bnrclass
.
The library syntax is buchnarrow(bnf)
.
(bnf)
bnf
being a big number field
output by bnfinit
, this computes an r_1 x (r_1+r_21)
matrix
having +1
components, giving the signs of the real embeddings of the
fundamental units.
The library syntax is signunits(bnf)
.
(bnf)
bnf
being a big number field
output by bnfinit
, computes its regulator.
The library syntax is regulator(bnf,tech,prec)
, where tech is as in
bnfclassunit
.
(bnf,S)
computes the fundamental S
units of the
number field bnf
(output by bnfinit
), where S
is a list of
prime ideals (output by idealprimedec
). The output is a vector v
with
6 components.
v[1]
gives a minimal system of (integral) generators of the S
unit group
modulo the unit group.
v[2]
contains technical data needed by bnfissunit
.
v[3]
is an empty vector (used to give the logarithmic embeddings of the
generators in v[1]
in version 2.0.16).
v[4]
is the S
regulator (this is the product of the regulator, the
determinant of v[2]
and the natural logarithms of the norms of the ideals
in S
).
v[5]
gives the S
class group structure, in the usual format
(a row vector whose three components give in order the S
class number,
the cyclic components and the generators).
v[6]
is a copy of S
.
The library syntax is bnfsunit(bnf,S,prec)
.
(bnf)
bnf
being a big number field as
output by
bnfinit
, outputs a twocomponent row vector giving in the first
component the vector of fundamental units of the number field, and in the
second component the number of bit of accuracy which remained in the
computation (which is always correct, otherwise an error message is printed).
This function is mainly for people who used the wrong flag in bnfinit
and would like to skip part of a lengthy bnfinit
computation.
The library syntax is buchfu(bnf)
.
(bnr,subgroup,{flag = 0})
bnr being the number field data which is output by
bnrinit(,,1)
and subgroup being a square matrix defining a
congruence subgroup of the ray class group corresponding to bnr
(or 0
for the trivial congruence subgroup), returns for each
character chi
of the ray class group which is trivial on this
subgroup, the value at s = 1
(or s = 0
) of the abelian
L
function associated to chi
. For the value at s = 0
, the
function returns in fact for each character chi
a vector [r_chi ,
c_F<chi>]
where r_chi
is the order of L(s, chi)
at s = 0
and
c_chi
the first nonzero term in the expansion of L(s,
F<chi>)
at s = 0
; in other words
L(s, chi) = c_chi.s^{r_chi} + O(s^{r_chi + 1})
near 0
. flag is optional, default value is 0; its binary digits
mean 1: compute at s = 1
if set to 1 or s = 0
if set to 0, 2: compute
the primitive L
functions associated to chi
if set to 0 or the
L
function with Euler factors at prime ideals dividing the modulus of
bnr removed if set to 1 (this is the socalled L_S(s, chi)
function where S
is the set of infinite places of the number field
together with the finite prime ideals dividing the modulus of bnr,
see the example below), 3: returns also the character.
Example:
bnf = bnfinit(x^2  229); bnr = bnrinit(bnf,1,1); bnrL1(bnr, 0)
returns the order and the first nonzero term of the abelian
L
functions L(s, chi)
at s = 0
where chi
runs through the
characters of the class group of Q( sqrt {229})
. Then
bnr2 = bnrinit(bnf,2,1); bnrL1(bnr2,0,2)
returns the order and the first nonzero terms of the abelian
L
functions L_S(s, chi)
at s = 0
where chi
runs through the
characters of the class group of Q( sqrt {229})
and S
is the set
of infinite places of Q( sqrt {229})
together with the finite prime
2
(note that the ray class group modulo 2
is in fact the class
group, so bnrL1(bnr2,0)
returns exactly the same answer as
bnrL1(bnr,0)
!).
The library syntax is bnrL1(bnr,subgroup,flag,prec)
(bnf,ideal,{flag = 0})
bnf
being a big number field
as output by bnfinit
(the units are mandatory unless the ideal is
trivial), and ideal being either an ideal in any form or a twocomponent
row vector containing an ideal and an r_1
component row vector of flags
indicating which real Archimedean embeddings to take in the module, computes
the ray class group of the number field for the module ideal, as a
3component vector as all other finite Abelian groups (cardinality, vector of
cyclic components, corresponding generators).
If flag = 2
, the output is different. It is a 6component vector w
. w[1]
is bnf
. w[2]
is the result of applying
idealstar(bnf,I,2)
. w[3]
, w[4]
and w[6]
are technical
components used only by the function bnrisprincipal
. w[5]
is the
structure of the ray class group as would have been output with flag = 0
.
If flag = 1
, as above, except that the generators of the ray class group are
not computed, which saves time.
The library syntax is bnrclass0(bnf,ideal,flag,prec)
.
(bnf,I)
bnf
being a big number field
as output
by bnfinit
(units are mandatory unless the ideal is trivial), and I
being either an ideal in any form or a twocomponent row vector containing an
ideal and an r_1
component row vector of flags indicating which real
Archimedean embeddings to take in the modulus, computes the ray class number
of the number field for the modulus I
. This is faster than bnrclass
and should be used if only the ray class number is desired.
The library syntax is rayclassno(bnf,I)
.
(bnf,list)
bnf
being a
big number field as output by bnfinit
(units are mandatory unless
the ideal is trivial), and list being a list of modules as output
by ideallist
of ideallistarch
,
outputs the list of the class numbers of the corresponding ray class groups.
The library syntax is rayclassnolist(bnf,list)
.
(a_1,{a_2},{a_3}, {flag = 0})
conductor of the
subfield of a ray class field as defined by [a_1,a_2,a_3]
(see bnr
at the beginning of this section).
The library syntax is bnrconductor(a_1,a_2,a_3,flag,prec)
, where an omitted argument
among the a_i
is input as gzero
, and flag
is a C long.
(bnr,chi)
bnr being a
big ray number field
as output by bnrclass
, and chi being a row vector representing a
character as expressed on the generators of the ray class group, gives
the conductor of this character as a modulus.
The library syntax is bnrconductorofchar(bnr,chi,prec)
where prec
is a long
.
(a1,{a2},{a3},{flag = 0})
a1
, a2
, a3
defining a big ray number field L
over a groud field K
(see bnr
at the beginning of this section for the
meaning of a1
, a2
, a3
), outputs a 3component row vector [N,R_1,D]
,
where N
is the (absolute) degree of L
, R_1
the number of real places of
L
, and D
the discriminant of L/Q
, including sign (if flag = 0
).
If flag = 1
, as above but outputs relative data. N
is now the degree of
L/K
, R_1
is the number of real places of K
unramified in L
(so that
the number of real places of L
is equal to R_1
times the relative degree
N
), and D
is the relative discriminant ideal of L/K
.
If flag = 2
, does as in case 0, except that if the modulus is not the exact
conductor corresponding to the L
, no data is computed and the result is 0
(gzero
).
If flag = 3
, as case 2, outputting relative data.
The library syntax is bnrdisc0(a1,a2,a3,flag,prec)
.
(bnf,bound,{arch},{flag = 0})
bnf
being a big
number field as output by bnfinit
(the units are mandatory), computes a
list of discriminants of Abelian extensions of the number field by increasing
modulus norm up to bound bound, where the ramified Archimedean places are
given by arch (unramified at infinity if arch is void or
omitted). If
flag is nonzero, give arch all the possible values. (See bnr
at the beginning of this section for the meaning of a1
, a2
, a3
.)
The alternative syntax bnrdisclist(bnf,list)
is supported, where list is as output by ideallist
or
ideallistarch
(with units).
The output format is as follows. The output v
is a row vector of row
vectors, allowing the bound to be greater than 2^{16}
for 32bit machines,
and v[i][j]
is understood to be in fact V[2^{15}(i1)+j]
of a unique big
vector V
(note that 2^{15}
is hardwired and can be increased in the
source code only on 64bit machines and higher).
Such a component V[k]
is itself a vector W
(maybe of length 0) whose
components correspond to each possible ideal of norm k
. Each component
W[i]
corresponds to an Abelian extension L
of bnf
whose modulus is
an ideal of norm k
and no Archimedean components (hence the extension is
unramified at infinity). The extension W[i]
is represented by a 4component
row vector [m,d,r,D]
with the following meaning. m
is the prime ideal
factorization of the modulus, d = [L:Q]
is the absolute degree of L
,
r
is the number of real places of L
, and D
is the factorization of the
absolute discriminant. Each prime ideal pr = [p,alpha,e,f,beta]
in the
prime factorization m
is coded as p.n^2+(f1).n+(j1)
, where
n
is the degree of the base field and j
is such that
pr = idealprimedec(nf,p)[j]
.
m
can be decoded using bnfdecodemodule
.
The library syntax is bnrdisclist0(a1,a2,a3,bound,arch,flag)
.
(bnf,ideal,{flag = 0})
bnf
is as
output by bnfinit
, ideal is a valid ideal (or a module),
initializes data linked
to the ray class group structure corresponding to this module. This is the
same as bnrclass(bnf,ideal,flag+1)
.
The library syntax is bnrinit0(bnf,ideal,flag,prec)
.
(a1,{a2},{a3})
a1
, a2
, a3
represent
an extension of the base field, given by class field theory for some modulus
encoded in the parameters. Outputs 1 if this modulus is the conductor, and 0
otherwise. This is slightly faster than bnrconductor
.
The library syntax is bnrisconductor(a1,a2,a3)
and the result is a long
.
(bnr,x,{flag = 1})
bnr being the
number field data which is output by bnrinit
(,,1)
and x
being an
ideal in any form, outputs the components of x
on the ray class group
generators in a way similar to bnfisprincipal
. That is a 3component
vector v
where v[1]
is the vector of components of x
on the ray class
group generators, v[2]
gives on the integral basis an element alpha
such
that x = alphaprod_ig_i^{x_i}
. Finally v[3]
indicates the number of bits
of accuracy left in the result. In any case the result is checked for
correctness, but v[3]
is included to see if it is necessary to increase the
accuracy in other computations.
If flag = 0
, outputs only v_1
. In that case, bnr need not contain the
ray class group generators, i.e. it may be created with bnrinit
(,,0)
The library syntax is isprincipalrayall(bnr,x,flag)
.
(bnr,chi,{flag = 0})
if chi = chi
is a (not necessarily primitive)
character over bnr, let
L(s,chi) = sum_{id} chi(id) N(id)^{s}
be the associated
Artin Lfunction. Returns the socalled Artin root number, i.e. the
complex number W(chi)
of modulus 1 such that
Lambda(1s,chi) = W(chi) Lambda(s,\overline{chi})
where Lambda(s,chi) = A(chi)^{s/2}gamma_chi(s) L(s,chi)
is
the enlarged Lfunction associated to L
.
The generators of the ray class group are needed, and you can set flag = 1
if
the character is known to be primitive. Example:
bnf = bnfinit(x^2  145); bnr = bnrinit(bnf,7,1); bnrrootnumber(bnr, [5])
returns the root number of the character chi
of Cl_7(Q( sqrt {145}))
such that chi(g) = zeta^5
, where g
is the generator of the rayclass
field and zeta = e^{2iPi/N}
where N
is the order of g
(N = 12
as
bnr.cyc
readily tells us).
The library syntax is bnrrootnumber(bnf,chi,flag)
{(bnr,subgroup,{flag = 0})}
bnr
being as output by bnrinit(,,1)
, finds a relative equation for the
class field corresponding to the modulus in bnr and the given
congruence subgroup using Stark units (set subgroup = 0
if you
want the whole ray class group). The main variable of bnr must not be
x
, and the ground field and the class field must be totally real and not
isomorphic to Q (over the rationnals, use polsubcyclo
or
galoissubcyclo
). flag is optional and may be set to 0 to obtain a
reduced relative polynomial, 1 to be satisfied with any relative
polynomial, 2 to obtain an absolute polynomial and 3 to obtain the
irreducible relative polynomial of the Stark unit, 0 being default.
Example:
bnf = bnfinit(y^2  3); bnr = bnrinit(bnf, 5, 1); bnrstark(bnr, 0)
returns the ray class field of Q( sqrt {3})
modulo 5
.
Remark. The result of the computation depends on the choice of
a modulus verifying special conditions. By default the function will try
few moduli, choosing the one giving the smallest result. In some cases
where the result is however very large, you can tell the function to
try more moduli by adding 4
to the value of flag. Whether this flag is
set or not, the function may fail in some extreme cases, returning the
error message
"Cannot find a suitable modulus in FindModule"
.
In this case, the corresponding congruence group is a product of cyclic groups and, for the time being, the class field has to be obtained by splitting this group into its cyclic components.
The library syntax is bnrstark(bnr,subgroup,flag)
.
(nf,b)
gives as a vector the first b
coefficients of the Dedekind zeta function of the number field nf
considered as a Dirichlet series.
The library syntax is dirzetak(nf,b)
.
(x,t)
factorization of the univariate polynomial x
over the number field defined by the (univariate) polynomial t
. x
may
have coefficients in Q or in the number field. The main variable of
t
must be of lower priority than that of x
(in other words the
variable number of t
must be greater than that of x
). However if
the coefficients of the number field occur explicitly (as polmods) as
coefficients of x
, the variable of these polmods must be the same as
the main variable of t
. For example
? factornf(x^2 + Mod(y, y^2+1), y^2+1); ? factornf(x^2 + 1, y^2+1); \\ these two are OK ? factornf(x^2 + Mod(z,z^2+1), y^2+1) *** incorrect type in gmulsg
The library syntax is polfnf(x,t)
.
(gal,perm,{fl = 0},{v = y}))
gal being be a Galois field as output by galoisinit
and
perm an element of gal.group
or a vector of such elements,
computes the fixed field of gal by the automorphism defined by the
permutations perm of the roots gal.roots
. P
is guaranteed to
be squarefree modulo gal.p
.
If no flags or flag = 0
, output format is the same as for nfsubfield
,
returning [P,x]
such that P
is a polynomial defining the fixed field, and
x
is a root of P
expressed as a polmod in gal.pol
.
If flag = 1
return only the polynomial P
.
If flag = 2
return [P,x,F]
where P
and x
are as above and F
is the
factorization of gal.pol
over the field defined by P
, where
variable v
(y
by default) stands for a root of P
. The priority of v
must be less than the priority of the variable of gal.pol
.
Example:
G = galoisinit(x^4+1); galoisfixedfield(G,G.group[2],2) [x^2 + 2, Mod(x^3 + x, x^4 + 1), [x^2  y*x  1, x^2 + y*x  1]]
computes the factorization x^4+1 = (x^2 sqrt {2}x1)(x^2+ sqrt {2}x1)
The library syntax is galoisfixedfield(gal,perm,p)
.
(pol,{den})
computes the Galois group
and all neccessary information for computing the fixed fields of the
Galois extension K/Q
where K
is the number field defined by
pol
(monic irreducible polynomial in Z[X]
or
a number field as output by nfinit
). The extension K/Q
must be
Galois with Galois group ``weakly'' supersolvable (see nfgaloisconj
)
Warning: The interface of this function is experimental,
so the described output can be subject to important changes in the
near future. However the function itself should work as described. For any
remarks about this interface, please mail allomber@math.ubordeaux.fr
.
The output is an 8component vector gal.
gal[1]
contains the polynomial pol
(gal.pol
).
gal[2]
is a threecomponents vector [p,e,q]
where p
is a
prime number (gal.p
) such that pol totally split
modulo p
, e
is an integer and q = p^e
(gal.mod
) is the
modulus of the roots in gal.roots
.
gal[3]
is a vector L
containing the p
adic roots of
pol as integers implicitly modulo gal.mod
.
(gal.roots
).
gal[4]
is the inverse of the Van der Monde matrix of the
p
adic roots of pol, multiplied by gal[5]
.
gal[5]
is a multiple of the least common denominator of the
automorphisms expressed as polynomial in a root of pol.
gal[6]
is the Galois group G
expressed as a vector of
permutations of L
(gal.group
).
gal[7]
is a generating subset S = [s_1,...,s_g]
of G
expressed as a vector of permutations of L
(gal.gen
).
gal[8]
contains the relative orders [o_1,...,o_g]
of
the generators of S
(gal.orders
).
Let H
be the maximal normal supersolvable subgroup of G
, we have the
following properties:
*
if G/H ~ A_4
then [o_1,...,o_g]
ends by
[2,2,3]
.
*
if G/H ~ S_4
then [o_1,...,o_g]
ends by
[2,2,3,2]
.
*
else G
is supersolvable.
*
for 1 <= i <= g
the subgroup of G
generated by
[s_1,...,s_g]
is normal, with the exception of i = g2
in the
second case and of i = g3
in the third.
*
the relative order o_i
of s_i
is its order in the
quotient group G/<s_1,...,s_{i1}>
, with the same
exceptions.
*
for any x belongs to G
there exists a unique family
[e_1,...,e_g]
such that (no exceptions):
 for 1 <= i <= g
we have 0 <= e_i < o_i
 x = g_1^{e_1}g_2^{e_2}...g_n^{e_n}
If present den
must be a suitable value for gal[5]
.
The library syntax is galoisinit(gal,den)
.
(gal,perm)
gal being a
galois field as output by galoisinit
and perm a element of
gal.group
, return the polynomial defining the Galois
automorphism, as output by nfgaloisconj
, associated with the
permutation perm of the roots gal.roots
. perm can
also be a vector or matrix, in this case, galoispermtopol
is
applied to all components recursively.
Note that
G = galoisinit(pol); galoispermtopol(G, G[6])~
is equivalent to nfgaloisconj(pol)
, if degree of pol
is greater or equal to 2
.
The library syntax is galoispermtopol(gal,perm)
.
(n,H,{Z},{v})
compute a polynomial
defining the subfield of Q(zeta_n)
fixed by the subgroup H of
Z/nZ
. The subgroup H can be given by a generator, a set of
generators given by a vector or a HNF matrix. If present Z
must be
znstar(n)
, and is currently only used when H is a HNF matrix. If
v is given, the polynomial is given in the variable v.
The following function can be used to compute all subfields of
Q(zeta_n)
(of order less than d
, if d
is set):
subcyclo(n, d = 1)= { local(Z,G,S); if (d < 0, d = n); Z = znstar(n); G = matdiagonal(Z[2]); S = []; forsubgroup(H = G, d, S = concat(S, galoissubcyclo(n, mathnf(concat(G,H)),Z)); ); S }
The library syntax is galoissubcyclo(n,H,Z,v)
where n is a C long integer.
(nf,x,y)
sum of the two ideals x
and y
in the
number field nf
. When x
and y
are given by Zbases, this does
not depend on nf
and can be used to compute the sum of any two
Zmodules. The result is given in HNF.
The library syntax is idealadd(nf,x,y)
.
(nf,x,{y})
x
and y
being two coprime
integral ideals (given in any form), this gives a twocomponent row vector
[a,b]
such that a belongs to x
, b belongs to y
and a+b = 1
.
The alternative syntax idealaddtoone(nf,v)
, is supported, where
v
is a k
component vector of ideals (given in any form) which sum to
Z_K
. This outputs a k
component vector e
such that e[i] belongs to x[i]
for
1 <= i <= k
and sum_{1 <= i <= k}e[i] = 1
.
The library syntax is idealaddtoone0(nf,x,y)
, where an omitted y
is coded as
NULL
.
(nf,x,{flag = 0})
if x
is a fractional ideal
(given in any form), gives an element alpha
in nf
such that for
all prime ideals p
such that the valuation of x
at p
is nonzero, we
have v_{p}(alpha) = v_{p}(x)
, and. v_{p}(alpha) >= 0
for all other
{p}
.
If flag
is nonzero, x
must be given as a prime ideal factorization, as
output by idealfactor
, but possibly with zero or negative exponents.
This yields an element alpha
such that for all prime ideals p
occurring
in x
, v_{p}(alpha)
is equal to the exponent of p
in x
, and for all
other prime ideals, v_{p}(alpha) >= 0
. This generalizes
idealappr(nf,x,0)
since zero exponents are allowed. Note that
the algorithm used is slightly different, so that
idealapp(nf,idealfactor(nf,x))
may not be the same as
idealappr(nf,x,1)
.
The library syntax is idealappr0(nf,x,flag)
.
(nf,x,y)
x
being a prime ideal factorization
(i.e. a 2 by 2 matrix whose first column contain prime ideals, and the second
column integral exponents), y
a vector of elements in nf
indexed by
the ideals in x
, computes an element b
such that
v_p(b  y_p) >= v_p(x)
for all prime ideals in x
and v_p(b) >= 0
for all other p
.
The library syntax is idealchinese(nf,x,y)
.
(nf,x,y)
given two integral ideals x
and y
in the number field nf
, finds a beta
in the field, expressed on the
integral basis nf[7]
, such that beta.y
is an integral ideal
coprime to x
.
The library syntax is idealcoprime(nf,x)
.
(nf,x,y,{flag = 0})
quotient x.y^{1}
of the
two ideals x
and y
in the number field nf
. The result is given in
HNF.
If flag
is nonzero, the quotient x.y^{1}
is assumed to be an
integral ideal. This can be much faster when the norm of the quotient is
small even though the norms of x
and y
are large.
The library syntax is idealdiv0(nf,x,y,flag)
. Also available
are idealdiv(nf,x,y)
(flag = 0
) and
idealdivexact(nf,x,y)
(flag = 1
).
(nf,x)
factors into prime ideal powers the
ideal x
in the number field nf
. The output format is similar to the
factor
function, and the prime ideals are represented in the form
output by the idealprimedec
function, i.e. as 5element vectors.
The library syntax is idealfactor(nf,x)
.
(nf,a,{b})
gives the Hermite normal form
matrix of the ideal a
. The ideal can be given in any form whatsoever
(typically by an algebraic number if it is principal, by a Z_K
system of
generators, as a prime ideal as given by idealprimedec
, or by a
Zbasis).
If b
is not omitted, assume the ideal given was aZ_K+bZ_K
, where a
and b
are elements of K
given either as vectors on the integral basis
nf[7]
or as algebraic numbers.
The library syntax is idealhnf0(nf,a,b)
where an omitted b
is coded as NULL
.
Also available is idealhermite(nf,a)
(b
omitted).
(nf,x,y)
intersection of the two ideals
x
and y
in the number field nf
. When x
and y
are given by
Zbases, this does not depend on nf
and can be used to compute the
intersection of any two Zmodules. The result is given in HNF.
The library syntax is idealintersect(nf,x,y)
.
(nf,x)
inverse of the ideal x
in the
number field nf
. The result is the Hermite normal form of the inverse
of the ideal, together with the opposite of the Archimedean information if it
is given.
The library syntax is idealinv(nf,x)
.
(nf,bound,{flag = 4})
computes the list
of all ideals of norm less or equal to bound in the number field
nf. The result is a row vector with exactly bound components.
Each component is itself a row vector containing the information about
ideals of a given norm, in no specific order. This information can be
either the HNF of the ideal or the idealstar
with possibly some
additional information.
If flag
is present, its binary digits are toggles meaning
1: give also the generators in the idealstar
.
2: output [L,U]
, where L
is as before and U
is a vector of
zinternallog
s of the units.
4: give only the ideals and not the idealstar
or the ideallog
of the units.
The library syntax is ideallist0(nf,bound,flag)
, where bound must
be a C long integer. Also available is ideallist(nf,bound)
,
corresponding to the case flag = 0
.
(nf,list,{arch = []},{flag = 0})
vector of vectors of all idealstarinit
(see idealstar
) of all
modules in list, with Archimedean part arch added (void if
omitted). list is a vector of big ideals, as output by
ideallist
(..., flag)
for instance. flag
is optional; its binary
digits are toggles meaning: 1: give generators as well, 2: list format is
[L,U]
(see ideallist
).
The library syntax is ideallistarch0(nf,list,arch,flag)
, where an omitted
arch is coded as NULL
.
(nf,x,bid)
nf
being a number field,
bid being a ``big ideal'' as output by idealstar
and x
being a
nonnecessarily integral element of nf which must have valuation
equal to 0 at all prime ideals dividing I = bid[1]
, computes the
``discrete logarithm'' of x
on the generators given in bid[2]
.
In other words, if g_i
are these generators, of orders d_i
respectively,
the result is a column vector of integers (x_i)
such that 0 <= x_i < d_i
and
x = prod_ig_i^{x_i} (mod ^*I) .
Note that when I
is a module, this implies also sign conditions on the
embeddings.
The library syntax is zideallog(nf,x,bid)
.
(nf,x,{vdir})
computes a minimum of
the ideal x
in the direction vdir in the number field nf.
The library syntax is minideal(nf,x,vdir,prec)
, where an omitted
vdir is coded as NULL
.
(nf,x,y,{flag = 0})
ideal multiplication of the
ideals x
and y
in the number field nf. The result is a generating
set for the ideal product with at most n
elements, and is in Hermite normal
form if either x
or y
is in HNF or is a prime ideal as output by
idealprimedec
, and this is given together with the sum of the
Archimedean information in x
and y
if both are given.
If flag
is nonzero, reduce the result using idealred
.
The library syntax is idealmul(nf,x,y)
(flag = 0
) or
idealmulred(nf,x,y,prec)
(flag ! = 0
), where as usual,
prec
is a C long integer representing the precision.
(nf,x)
computes the norm of the ideal x
in the number field nf
.
The library syntax is idealnorm(nf, x)
.
(nf,x,k,{flag = 0})
computes the k
th power of
the ideal x
in the number field nf
. k
can be positive, negative
or zero. The result is NOT reduced, it is really the k
th ideal power, and
is given in HNF.
If flag
is nonzero, reduce the result using idealred
. Note however
that this is NOT the same as as idealpow(nf,x,k)
followed by
reduction, since the reduction is performed throughout the powering process.
The library syntax corresponding to flag = 0
is
idealpow(nf,x,k)
. If k
is a long
, you can use
idealpows(nf,x,k)
. Corresponding to flag = 1
is
idealpowred(nf,vp,k,prec)
, where prec
is a
long
.
(nf,p)
computes the prime ideal
decomposition of the prime number p
in the number field nf
. p
must be a (positive) prime number. Note that the fact that p
is prime is
not checked, so if a nonprime number p
is given it may lead to
unpredictable results.
The result is a vector of 5component vectors, each representing one of the
prime ideals above p
in the number field nf
. The representation
vp = [p,a,e,f,b]
of a prime ideal means the following. The prime ideal is
equal to pZ_K+alphaZ_K
where Z_K
is the ring of integers of the field
and alpha = sum_i a_iomega_i
where the omega_i
form the integral basis
nf.zk
, e
is the ramification index, f
is the residual index,
and b
is an n
component column vector representing a beta belongs to Z_K
such
that vp^{1} = Z_K+beta/pZ_K
which will be useful for computing
valuations, but which the user can ignore. The number alpha
is guaranteed
to have a valuation equal to 1 at the prime ideal (this is automatic if
e > 1
).
The library syntax is idealprimedec(nf,p)
.
(nf,x)
creates the principal ideal
generated by the algebraic number x
(which must be of type integer,
rational or polmod) in the number field nf
. The result is a
onecolumn matrix.
The library syntax is principalideal(nf,x)
.
(nf,I,{vdir = 0})
LLL reduction of
the ideal I
in the number field nf, along the direction vdir.
If vdir is present, it must be an r1+r2
component vector (r1
and
r2
number of real and complex places of nf as usual).
This function finds a ``small'' a
in I
(it is an LLL pseudominimum
along direction vdir). The result is the Hermite normal form of
the LLLreduced ideal r I/a
, where r
is a rational number such that the
resulting ideal is integral and primitive. This is often, but not always, a
reduced ideal in the sense of Buchmann. If I
is an idele, the
logarithmic embeddings of a
are subtracted to the Archimedean part.
More often than not, a principal ideal will yield the identity
matrix. This is a quick and dirty way to check if ideals are principal
without computing a full bnf
structure, but it's not a necessary
condition; hence, a nontrivial result doesn't prove the ideal is
nontrivial in the class group.
Note that this is not the same as the LLL reduction of the lattice
I
since ideal operations are involved.
The library syntax is ideallllred(nf,x,vdir,prec)
, where an omitted
vdir is coded as NULL
.
(nf,I,{flag = 1})
nf being a number
field, and I
either and ideal in any form, or a row vector whose first component is an
ideal and whose second component is a row vector of r_1
0 or 1, outputs
necessary data for computing in the group (Z_K/I)^*
.
If flag = 2
, the result is a 5component vector w
. w[1]
is the ideal
or module I
itself. w[2]
is the structure of the group. The other
components are difficult to describe and are used only in conjunction with
the function ideallog
.
If flag = 1
(default), as flag = 2
, but do not compute explicit generators
for the cyclic components, which saves time.
If flag = 0
, computes the structure of (Z_K/I)^*
as a 3component vector
v
. v[1]
is the order, v[2]
is the vector of SNF
cyclic components and
v[3]
the corresponding generators. When the row vector is explicitly
included, the
nonzero elements of this vector are considered as real embeddings of
nf in the order given by polroots
, i.e. in nf[6]
(nf.roots
), and then I
is a module with components at infinity.
To solve discrete logarithms (using ideallog
), you have to choose
flag = 2
.
The library syntax is idealstar0(nf,I,flag)
.
(nf,x,{a})
computes a twoelement
representation of the ideal x
in the number field nf
, using a
straightforward (exponential time) search. x
can be an ideal in any form,
(including perhaps an Archimedean part, which is ignored) and the result is a
row vector [a,alpha]
with two components such that x = aZ_K+alphaZ_K
and a belongs to Z
, where a
is the one passed as argument if any. If x
is given
by at least two generators, a
is chosen to be the positive generator of
x cap Z
.
Note that when an explicit a
is given, we use an asymptotically faster
method, however in practice it is usually slower.
The library syntax is ideal_two_elt0(nf,x,a)
, where an omitted a
is entered as
NULL
.
(nf,x,vp)
gives the valuation of the
ideal x
at the prime ideal vp in the number field nf
,
where vp must be a
5component vector as given by idealprimedec
.
The library syntax is idealval(nf,x,vp)
, and the result is a long
integer.
(nf,x)
creates the principal idele
generated by the algebraic number x
(which must be of type integer,
rational or polmod) in the number field nf
. The result is a
twocomponent vector, the first being a onecolumn matrix representing the
corresponding principal ideal, and the second being the vector with r_1+r_2
components giving the complex logarithmic embedding of x
.
The library syntax is principalidele(nf,x)
.
(nf,x)
nf
being a number field in
nfinit
format, and x
a matrix whose coefficients are expressed as
polmods in nf
, transforms this matrix into a matrix whose
coefficients are expressed on the integral basis of nf
. This is the
same as applying nfalgtobasis
to each entry, but it would be dangerous
to use the same name.
The library syntax is matalgtobasis(nf,x)
.
(nf,x)
nf
being a number field in
nfinit
format, and x
a matrix whose coefficients are expressed as
column vectors on the integral basis of nf
, transforms this matrix
into a matrix whose coefficients are algebraic numbers expressed as
polmods. This is the same as applying nfbasistoalg
to each entry, but
it would be dangerous to use the same name.
The library syntax is matbasistoalg(nf,x)
.
(a)
a
being a polmod A(X)
modulo T(X)
, finds
the ``reverse polmod'' B(X)
modulo Q(X)
, where Q
is the minimal
polynomial of a
, which must be equal to the degree of T
, and such that if
theta
is a root of T
then theta = B(alpha)
for a certain root alpha
of Q
.
This is very useful when one changes the generating element in algebraic extensions.
The library syntax is polmodrecip(x)
.
(x,p)
gives the vector of the slopes of the Newton
polygon of the polynomial x
with respect to the prime number p
. The n
components of the vector are in decreasing order, where n
is equal to the
degree of x
. Vertical slopes occur iff the constant coefficient of x
is
zero and are denoted by VERYBIGINT
, the biggest single precision
integer representable on the machine (2^{31}1
(resp. 2^{63}1
) on 32bit
(resp. 64bit) machines), see Label se:valuation.
The library syntax is newtonpoly(x,p)
.
(nf,x)
this is the inverse function of
nfbasistoalg
. Given an object x
whose entries are expressed as
algebraic numbers in the number field nf
, transforms it so that the
entries are expressed as a column vector on the integral basis
nf.zk
.
The library syntax is algtobasis(nf,x)
.
(x,{flag = 0},{p})
integral basis of the number
field defined by the irreducible, preferably monic, polynomial x
,
using a modified version of the round 4 algorithm by
default. The binary digits of flag
have the following meaning:
1: assume that no square of a prime greater than the default primelimit
divides the discriminant of x
, i.e. that the index of x
has only small
prime divisors.
2: use round 2 algorithm. For small degrees and coefficient size, this is sometimes a little faster. (This program is the translation into C of a program written by David Ford in Algeb.)
Thus for instance, if flag = 3
, this uses the round 2 algorithm and outputs
an order which will be maximal at all the small primes.
If p
is present, we assume (without checking!) that it is the twocolumn
matrix of the factorization of the discriminant of the polynomial x
. Note
that it does not have to be a complete factorization. This is
especially useful if only a local integral basis for some small set of places
is desired: only factors with exponents greater or equal to 2 will be
considered.
The library syntax is nfbasis0(x,flag,p)
. An extended version
is nfbasis(x,&d,flag,p)
, where d
will receive the discriminant of
the number field (not of the polynomial x
), and an omitted p
should
be input as gzero
. Also available are base(x,&d)
(flag = 0
),
base2(x,&d)
(flag = 2
) and factoredbase(x,p,&d)
.
(nf,x)
this is the inverse function of
nfalgtobasis
. Given an object x
whose entries are expressed on the
integral basis nf.zk
, transforms it into an object whose entries
are algebraic numbers (i.e. polmods).
The library syntax is basistoalg(nf,x)
.
(nf,x)
given a pseudomatrix x
, computes a
nonzero ideal contained in (i.e. multiple of) the determinant of x
. This
is particularly useful in conjunction with nfhnfmod
.
The library syntax is nfdetint(nf,x)
.
(x,{flag = 0},{p})
field discriminant of the
number field defined by the integral, preferably monic, irreducible
polynomial x
. flag
and p
are exactly as in nfbasis
. That is, p
provides the matrix of a partial factorization of the discriminant of x
,
and binary digits of flag
are as follows:
1: assume that no square of a prime greater than primelimit
divides the discriminant.
2: use the round 2 algorithm, instead of the default round 4. This should be slower except maybe for polynomials of small degree and coefficients.
The library syntax is nfdiscf0(x,flag,p)
where, to omit p
, you should input gzero
. You
can also use discf(x)
(flag = 0
).
(nf,x,y)
given two elements x
and y
in
nf, computes their quotient x/y
in the number field nf
.
The library syntax is element_div(nf,x,y)
.
(nf,x,y)
given two elements x
and y
in
nf, computes an algebraic integer q
in the number field nf
such that the components of xqy
are reasonably small. In fact, this is
functionally identical to round(nfeltdiv(nf,x,y))
.
The library syntax is nfdiveuc(nf,x,y)
.
(nf,x,y,pr)
given two elements x
and y
in nf and pr a prime ideal in modpr
format (see
nfmodprinit
), computes their quotient x / y
modulo the prime ideal
pr.
The library syntax is element_divmodpr(nf,x,y,pr)
.
(nf,x,y)
given two elements x
and y
in
nf, gives a twoelement row vector [q,r]
such that x = qy+r
, q
is
an algebraic integer in nf
, and the components of r
are
reasonably small.
The library syntax is nfdivres(nf,x,y)
.
(nf,x,y)
given two elements x
and y
in
nf, computes an element r
of nf
of the form r = xqy
with
q
and algebraic integer, and such that r
is small. This is functionally
identical to
x  nfeltmul(nf,round(nfeltdiv(nf,x,y)),y).
The library syntax is nfmod(nf,x,y)
.
(nf,x,y)
given two elements x
and y
in
nf, computes their product x*y
in the number field nf
.
The library syntax is element_mul(nf,x,y)
.
(nf,x,y,pr)
given two elements x
and
y
in nf and pr a prime ideal in modpr
format (see
nfmodprinit
), computes their product x*y
modulo the prime ideal
pr.
The library syntax is element_mulmodpr(nf,x,y,pr)
.
(nf,x,k)
given an element x
in nf,
and a positive or negative integer k
, computes x^k
in the number field
nf
.
The library syntax is element_pow(nf,x,k)
.
(nf,x,k,pr)
given an element x
in
nf, an integer k
and a prime ideal pr in modpr
format
(see nfmodprinit
), computes x^k
modulo the prime ideal pr.
The library syntax is element_powmodpr(nf,x,k,pr)
.
(nf,x,ideal)
given an ideal in
Hermite normal form and an element x
of the number field nf
,
finds an element r
in nf
such that xr
belongs to the ideal
and r
is small.
The library syntax is element_reduce(nf,x,ideal)
.
(nf,x,pr)
given
an element x
of the number field nf
and a prime ideal pr in
modpr
format compute a canonical representative for the class of x
modulo pr.
The library syntax is nfreducemodpr2(nf,x,pr)
.
(nf,x,pr)
given an element x
in
nf and a prime ideal pr in the format output by
idealprimedec
, computes their the valuation at pr of the
element x
. The same result could be obtained using
idealval(nf,x,pr)
(since x
would then be converted to a
principal ideal), but it would be less efficient.
The library syntax is element_val(nf,x,pr)
, and the result is a long
.
(nf,x)
factorization of the univariate
polynomial x
over the number field nf
given by nfinit
. x
has coefficients in nf
(i.e. either scalar, polmod, polynomial or
column vector). The main variable of nf
must be of lower
priority than that of x
(in other words, the variable number of nf
must be greater than that of x
). However if the polynomial defining
the number field occurs explicitly in the coefficients of x
(as modulus of
a t_POLMOD
), its main variable must be the same as the main
variable of x
. For example,
? nf = nfinit(y^2 + 1); ? nffactor(nf, x^2 + y); \\ OK ? nffactor(nf, x^2 + Mod(y, y^2+1)); \\ OK ? nffactor(nf, x^2 + Mod(z, z^2+1)); \\ WRONG
The library syntax is nffactor(nf,x)
.
(nf,x,pr)
factorization of the
univariate polynomial x
modulo the prime ideal pr in the number
field nf
. x
can have coefficients in the number field (scalar,
polmod, polynomial, column vector) or modulo the prime ideal (integermod
modulo the rational prime under pr, polmod or polynomial with
integermod coefficients, column vector of integermod). The prime ideal
pr must be in the format output by idealprimedec
. The
main variable of nf
must be of lower priority than that of x
(in
other words the variable number of nf
must be greater than that of
x
). However if the coefficients of the number field occur explicitly (as
polmods) as coefficients of x
, the variable of these polmods must
be the same as the main variable of t
(see nffactor
).
The library syntax is nffactormod(nf,x,pr)
.
(nf,aut,x)
nf
being a
number field as output by nfinit
, and aut being a Galois
automorphism of nf
expressed either as a polynomial or a polmod
(such automorphisms being found using for example one of the variants of
nfgaloisconj
), computes the action of the automorphism aut on
the object x
in the number field. x
can be an element (scalar, polmod,
polynomial or column vector) of the number field, an ideal (either given by
Z_K
generators or by a Zbasis), a prime ideal (given as a 5element
row vector) or an idele (given as a 2element row vector). Because of
possible confusion with elements and ideals, other vector or matrix
arguments are forbidden.
The library syntax is galoisapply(nf,aut,x)
.
(nf,{flag = 0},{d})
nf
being a
number field as output by nfinit
, computes the conjugates of a root
r
of the nonconstant polynomial x = nf[1]
expressed as
polynomials in r
. This can be used even if the number field nf
is
not Galois since some conjugates may lie in the field. As a note to
oldtimers of PARI, starting with version 2.0.17 this function works much
better than in earlier versions.
nf
can simply be a polynomial if flag ! = 1
.
If no flags or flag = 0
, if nf
is a number field use a
combination of flag 4
and 1
and the result is always complete,
else use a combination of flag 4
and 2
and the result is subject
to the restriction of flag = 2
, but a warning is issued when it is not
proven complete.
If flag = 1
, use nfroots
(require a number field).
If flag = 2
, use complex approximations to the roots and an integral
LLL. The result is not guaranteed to be complete: some
conjugates may be missing (no warning issued), especially so if the
corresponding polynomial has a huge index. In that case, increasing
the default precision may help.
If flag = 4
, use Allombert's algorithm and permutation testing. If the
field is Galois with ``weakly'' super solvable Galois group, return
the complete list of automorphisms, else only the identity element. If
present, d
is assumed to be a multiple of the least common
denominator of the conjugates expressed as polynomial in a root of
pol.
A group G is ``weakly'' super solvable if it contains a super solvable
normal subgroup H
such that G = H
, or G/H ~ A_4
, or G/H ~
S_4
. Abelian and nilpotent groups are ``weakly'' super solvable. In
practice, almost all groups of small order are ``weakly'' super solvable, the
exceptions having order 36(1 exception), 48(2), 56(1), 60(1), 72(5), 75(1),
80(1), 96(10)
and >= 108
.
Hence flag = 4
permits to quickly check whether a polynomial of order
strictly less than 36
is Galois or not. This method is much faster than
nfroots
and can be applied to polynomials of degree larger than 50
.
The library syntax is galoisconj0(nf,flag,d,prec)
. Also available are
galoisconj(nf)
for flag = 0
,
galoisconj2(nf,n,prec)
for flag = 2
where n
is a bound
on the number of conjugates, and galoisconj4(nf,d)
corresponding to flag = 4
.
(nf,a,b,{pr})
if pr is omitted,
compute the global Hilbert symbol (a,b)
in nf
, that is 1
if x^2  a y^2  b z^2
has a non trivial solution (x,y,z)
in nf
,
and 1
otherwise. Otherwise compute the local symbol modulo the prime ideal
pr (as output by idealprimedec
).
The library syntax is nfhilbert(nf,a,b,pr)
, where an omitted pr is coded
as NULL
.
(nf,x)
given a pseudomatrix (A,I)
, finds a
pseudobasis in Hermite normal form of the module it generates.
The library syntax is nfhermite(nf,x)
.
(nf,x,detx)
given a pseudomatrix (A,I)
and an ideal detx which is contained in (read integral multiple of) the
determinant of (A,I)
, finds a pseudobasis in Hermite normal form
of the module generated by (A,I)
. This avoids coefficient explosion.
detx can be computed using the function nfdetint
.
The library syntax is nfhermitemod(nf,x,detx)
.
(pol,{flag = 0})
pol being a nonconstant,
preferably monic, irreducible polynomial in Z[X]
, initializes a
number field structure (nf
) associated to the field K
defined
by pol. As such, it's a technical object passed as the first argument
to most nf
xxx functions, but it contains some information which
may be directly useful. Access to this information via member
functions is prefered since the specific data organization specified below
may change in the future. Currently, nf
is a row vector with 9
components:
nf[1]
contains the polynomial pol (nf.pol
).
nf[2]
contains [r1,r2]
(nf.sign
), the number of real
and complex places of K
.
nf[3]
contains the discriminant d(K)
(nf.disc
) of K
.
nf[4]
contains the index of nf[1]
,
i.e. [Z_K : Z[theta]]
, where theta
is any root of nf[1]
.
nf[5]
is a vector containing 7 matrices M
, MC
, T2
, T
,
MD
, TI
, MDI
useful for certain computations in the number field K
.
*
M
is the (r1+r2) x n
matrix whose columns represent
the numerical values of the conjugates of the elements of the integral
basis.
*
MC
is essentially the conjugate of the transpose of M
,
except that the last r2
columns are also multiplied by 2.
*
T2
is an n x n
matrix equal to the real part of the
product MC.M
(which is a real positive definite symmetric matrix), the
socalled T_2
matrix (nf.t2
).
*
T
is the n x n
matrix whose coefficients are
Tr(omega_iomega_j)
where the omega_i
are the elements of the
integral basis. Note that T = \overline{MC}.M
and in particular that
T = T_2
if the field is totally real (in practice T_2
will have real
approximate entries and T
will have integer entries). Note also that
det (T)
is equal to the discriminant of the field K
.
*
The columns of MD
(nf.diff
) express a Zbasis
of the different of K
on the integral basis.
*
TI
is equal to d(K)T^{1}
, which has integral
coefficients. Note that, understood as as ideal, the matrix T^{1}
generates the codifferent ideal.
*
Finally, MDI
is a twoelement representation (for faster
ideal product) of d(K)
times the codifferent ideal
(nf.disc*nf.codiff
, which is an integral ideal). MDI
is only used in idealinv
.
nf[6]
is the vector containing the r1+r2
roots
(nf.roots
) of nf[1]
corresponding to the r1+r2
embeddings of the number field into C (the first r1
components are real,
the next r2
have positive imaginary part).
nf[7]
is an integral basis in Hermite normal form for Z_K
(nf.zk
) expressed on the powers of theta
.
nf[8]
is the n x n
integral matrix expressing the power
basis in terms of the integral basis, and finally
nf[9]
is the n x n^2
matrix giving the multiplication table
of the integral basis.
If a non monic polynomial is input, nfinit
will transform it into a
monic one, then reduce it (see flag = 3
). It is allowed, though not very
useful given the existence of nfnewprec, to input a nf
or a
bnf
instead of a polynomial.
The special input format [x,B]
is also accepted where x
is a polynomial
as above and B
is the integer basis, as computed by nfbasis
. This can
be useful since nfinit
uses the round 4 algorithm by default, which can
be very slow in pathological cases where round 2 (nfbasis(x,2)
) would
succeed very quickly.
If flag = 2
: pol is changed into another polynomial P
defining the same
number field, which is as simple as can easily be found using the
polred
algorithm, and all the subsequent computations are done using
this new polynomial. In particular, the first component of the result is the
modified polynomial.
If flag = 3
, does a polred
as in case 2, but outputs
[nf,Mod(a,P)]
, where nf
is as before and
Mod(a,P) = Mod(x,pol)
gives the change of
variables. This is implicit when pol is not monic: first a linear change
of variables is performed, to get a monic polynomial, then a polred
reduction.
If flag = 4
, as 2
but uses a partial polred
.
If flag = 5
, as 3
using a partial polred
.
The library syntax is nfinit0(x,flag,prec)
.
(nf,x)
returns 1 if x
is an ideal in
the number field nf
, 0 otherwise.
The library syntax is isideal(x)
.
(x,y)
tests whether the number field K
defined
by the polynomial x
is conjugate to a subfield of the field L
defined
by y
(where x
and y
must be in Q[X]
). If they are not, the output
is the number 0. If they are, the output is a vector of polynomials, each
polynomial a
representing an embedding of K
into L
, i.e. being such
that y  x o a
.
If y
is a number field (nf), a much faster algorithm is used
(factoring x
over y
using nffactor
). Before version 2.0.14, this
wasn't guaranteed to return all the embeddings, hence was triggered by a
special flag. This is no more the case.
The library syntax is nfisincl(x,y,flag)
.
(x,y)
as nfisincl
, but tests
for isomorphism. If either x
or y
is a number field, a much faster
algorithm will be used.
The library syntax is nfisisom(x,y,flag)
.
(nf)
transforms the number field nf
into the corresponding data using current (usually larger) precision. This
function works as expected if nf
is in fact a bnf
(update
bnf
to current precision) but may be quite slow (many generators of
principal ideals have to be computed).
The library syntax is nfnewprec(nf,prec)
.
(nf,a,pr)
kernel of the matrix a
in
Z_K/pr
, where pr is in modpr format
(see nfmodprinit
).
The library syntax is nfkermodpr(nf,a,pr)
.
(nf,pr)
transforms the prime ideal
pr into modpr
format necessary for all operations modulo
pr in the number field nf. Returns a twocomponent vector
[P,a]
, where P
is the Hermite normal form of pr, and a
is
an integral element congruent to 1
modulo pr, and congruent to 0
modulo p / pr^e
. Here p = Z cap pr
and e
is the absolute ramification index.
The library syntax is nfmodprinit(nf,pr)
.
(nf,{d = 0})
finds all subfields of degree d
of the number field nf
(all subfields if d
is null or omitted).
The result is a vector of subfields, each being given by [g,h]
, where g
is an
absolute equation and h
expresses one of the roots of g
in terms of the
root x
of the polynomial defining nf
. This is a crude
implementation by M. Olivier of an algorithm due to J. Klüners.
The library syntax is subfields(nf,d)
.
(nf,x)
roots of the polynomial x
in the number
field nf
given by nfinit
without multiplicity. x
has
coefficients in the number field (scalar, polmod, polynomial, column
vector). The main variable of nf
must be of lower priority than that
of x
(in other words the variable number of nf
must be greater than
that of x
). However if the coefficients of the number field occur
explicitly (as polmods) as coefficients of x
, the variable of these
polmods must be the same as the main variable of t
(see
nffactor
).
The library syntax is nfroots(nf,x)
.
(nf)
computes the number of roots of unity
w
and a primitive w
th root of unity (expressed on the integral basis)
belonging to the number field nf
. The result is a twocomponent
vector [w,z]
where z
is a column vector expressing a primitive w
th
root of unity on the integral basis nf.zk
.
The library syntax is rootsof1(nf)
.
(nf,x)
given a torsion module x
as a 3component
row
vector [A,I,J]
where A
is a square invertible n x n
matrix, I
and
J
are two ideal lists, outputs an ideal list d_1,...,d_n
which is the
Smith normal form of x
. In other words, x
is isomorphic to
Z_K/d_1 oplus ... oplus Z_K/d_n
and d_i
divides d_{i1}
for i >= 2
.
The link between x
and [A,I,J]
is as follows: if e_i
is the canonical
basis of K^n
, I = [b_1,...,b_n]
and J = [a_1,...,a_n]
, then x
is
isomorphic to
(b_1e_1 oplus ... oplus b_ne_n) / (a_1A_1 oplus ... oplus a_nA_n)
,
where the A_j
are the columns of the matrix A
. Note that every finitely
generated torsion module can be given in this way, and even with b_i = Z_K
for all i
.
The library syntax is nfsmith(nf,x)
.
(nf,a,b,pr)
solution of a.x = b
in Z_K/pr
, where a
is a matrix and b
a column vector, and where
pr is in modpr format (see nfmodprinit
).
The library syntax is nfsolvemodpr(nf,a,b,pr)
.
(x,y,{flag = 0})
x
and y
being polynomials
in Z[X]
in the same variable, outputs a vector giving the list of all
possible composita of the number fields defined by x
and y
, if x
and
y
are irreducible, or of the corresponding étale algebras, if they are
only squarefree. Returns an error if one of the polynomials is not
squarefree. When one of the polynomials is irreducible (say x
), it is
often much faster to use nffactor(nfinit(x), y)
then
rnfequation
.
If flag = 1
, outputs a vector of 4component vectors [z,a,b,k]
, where z
ranges through the list of all possible compositums as above, and a
(resp. b
) expresses the root of x
(resp. y
) as a polmod in a root of
z
, and k
is a small integer k such that a+kb
is the chosen root of
z
.
The compositum will quite often be defined by a complicated polynomial,
which it is advisable to reduce before further work. Here is a simple
example involving the field Q(zeta_5, 5^{1/5})
:
? z = polcompositum(x^5  5, polcyclo(5), 1)[1]; ? pol = z[1] \\ pol defines the compositum %2 = x^20 + 5*x^19 + 15*x^18 + 35*x^17 + 70*x^16 + 141*x^15 + 260*x^14 \ + 355*x^13 + 95*x^12  1460*x^11  3279*x^10  3660*x^9  2005*x^8 \ + 705*x^7 + 9210*x^6 + 13506*x^5 + 7145*x^4  2740*x^3 + 1040*x^2 \  320*x + 256 ? a = z[2]; a^5  5 \\ a is a fifth root of 5 %3 = 0 ? z = polredabs(pol, 1); \\ look for a simpler polynomial ? pol = z[1] %5 = x^20 + 25*x^10 + 5 ? a = subst(a.pol, x, z[2]) \\ a in the new coordinates %6 = Mod(5/22*x^19 + 1/22*x^14  123/22*x^9 + 9/11*x^4, x^20 + 25*x^10 + 5)
The library syntax is polcompositum0(x,y,flag)
.
(x)
Galois group of the nonconstant polynomial
x belongs to Q[X]
. In the present version 2.2.0, x
must be irreducible and
the degree of x
must be less than or equal to 7. On certain versions for
which the data file of Galois resolvents has been installed (available
in the Unix distribution as a separate package), degrees 8, 9, 10 and 11
are also implemented.
The output is a 3component vector [n,s,k]
with the following meaning: n
is the cardinality of the group, s
is its signature (s = 1
if the group is
a subgroup of the alternating group A_n
, s = 1
otherwise), and k
is the
number of the group corresponding to a given pair (n,s)
(k = 1
except in 2
cases). Specifically, the groups are coded as follows, using standard
notations (see GTM 138, quoted at the beginning of this section; see also
``The transitive groups of degree up to eleven'', by G. Butler and J. McKay
in Communications in Algebra, vol. 11, 1983, pp. 863911):
In degree 1: S_1 = [1,1,1]
.
In degree 2: S_2 = [2,1,1]
.
In degree 3: A_3 = C_3 = [3,1,1]
, S_3 = [6,1,1]
.
In degree 4: C_4 = [4,1,1]
, V_4 = [4,1,1]
, D_4 = [8,1,1]
, A_4 = [12,1,1]
,
S_4 = [24,1,1]
.
In degree 5: C_5 = [5,1,1]
, D_5 = [10,1,1]
, M_{20} = [20,1,1]
,
A_5 = [60,1,1]
, S_5 = [120,1,1]
.
In degree 6: C_6 = [6,1,1]
, S_3 = [6,1,2]
, D_6 = [12,1,1]
, A_4 = [12,1,1]
,
G_{18} = [18,1,1]
, S_4^ = [24,1,1]
, A_4 x C_2 = [24,1,2]
,
S_4^ += [24,1,1]
, G_{36}^ = [36,1,1]
, G_{36}^ += [36,1,1]
,
S_4 x C_2 = [48,1,1]
, A_5 = PSL_2(5) = [60,1,1]
, G_{72} = [72,1,1]
,
S_5 = PGL_2(5) = [120,1,1]
, A_6 = [360,1,1]
, S_6 = [720,1,1]
.
In degree 7: C_7 = [7,1,1]
, D_7 = [14,1,1]
, M_{21} = [21,1,1]
,
M_{42} = [42,1,1]
, PSL_2(7) = PSL_3(2) = [168,1,1]
, A_7 = [2520,1,1]
,
S_7 = [5040,1,1]
.
The method used is that of resolvent polynomials and is sensitive to the current precision. The precision is updated internally but, in very rare cases, a wrong result may be returned if the initial precision was not sufficient.
The library syntax is galois(x,prec)
.
(x,{flag = 0},{p})
finds polynomials with reasonably
small coefficients defining subfields of the number field defined by x
.
One of the polynomials always defines Q (hence is equal to x1
),
and another always defines the same number field as x
if x
is irreducible.
All x
accepted by nfinit
are also allowed here (e.g. nonmonic
polynomials, nf
, bnf
, [x,Z_K_basis]
).
The following binary digits of flag
are significant:
1: does a partial reduction only. This means that only a suborder of the maximal order may be used.
2: gives also elements. The result is a twocolumn matrix, the first column giving the elements defining these subfields, the second giving the corresponding minimal polynomials.
If p
is given, it is assumed that it is the twocolumn matrix of the
factorization of the discriminant of the polynomial x
.
The library syntax is polred0(x,flag,p,prec)
, where an omitted p
is
coded by gzero
. Also available are polred(x,prec)
and
factoredpolred(x,p,prec)
, both corresponding to flag = 0
.
(x,{flag = 0})
finds one of the polynomial defining
the same number field as the one defined by x
, and such that the sum of the
squares of the modulus of the roots (i.e. the T_2
norm) is minimal.
All x
accepted by nfinit
are also allowed here (e.g. nonmonic
polynomials, nf
, bnf
, [x,Z_K_basis]
).
The binary digits of flag
mean
1: outputs a twocomponent row vector [P,a]
, where P
is the default
output and a
is an element expressed on a root of the polynomial P
,
whose minimal polynomial is equal to x
.
4: gives all polynomials of minimal T_2
norm (of the two polynomials
P(x)
and P(x)
, only one is given).
The library syntax is polredabs0(x,flag,prec)
.
(x)
finds polynomials with reasonably small
coefficients and of the same degree as that of x
defining suborders of the
order defined by x
. One of the polynomials always defines Q (hence
is equal to (x1)^n
, where n
is the degree), and another always defines
the same order as x
if x
is irreducible.
The library syntax is ordred(x)
.
(x)
applies a random Tschirnhausen
transformation to the polynomial x
, which is assumed to be nonconstant
and separable, so as to obtain a new equation for the étale algebra
defined by x
. This is for instance useful when computing resolvents,
hence is used by the polgalois
function.
The library syntax is tschirnhaus(x)
.
(rnf,x)
rnf
being a relative number
field extension L/K
as output by rnfinit
and x
being an element of
L
expressed as a polynomial or polmod with polmod coefficients, expresses
x
on the relative integral basis.
The library syntax is rnfalgtobasis(rnf,x)
.
(bnf,x)
given a big number field bnf
as
output by bnfinit
, and either a polynomial x
with coefficients in
bnf
defining a relative extension L
of bnf
, or a
pseudobasis x
of such an extension, gives either a true bnf
basis
of L
if it exists, or an n+1
element generating set of L
if not, where
n
is the rank of L
over bnf
.
The library syntax is rnfbasis(bnf,x)
.
(rnf,x)
rnf
being a relative number
field extension L/K
as output by rnfinit
and x
being an element of
L
expressed on the relative integral basis, computes the representation of
x
as a polmod with polmods coefficients.
The library syntax is rnfbasistoalg(rnf,x)
.
(nf,T,a,{v = x})
characteristic polynomial of
a
over nf
, where a
belongs to the algebra defined by T
over
nf
, i.e. nf[X]/(T)
. Returns a polynomial in variable v
(x
by default).
The library syntax is rnfcharpoly(nf,T,a,v)
, where v
is a variable number.
(bnf,pol)
bnf
being a big number
field as output by bnfinit
, and pol a relative polynomial defining
an Abelian extension, computes the class field theory conductor of this
Abelian extension. The result is a 3component vector
[conductor,rayclgp,subgroup]
, where conductor is
the conductor of the extension given as a 2component row vector
[f_0,f_ oo ]
, rayclgp is the full ray class group corresponding to
the conductor given as a 3component vector [h,cyc,gen] as usual for a group,
and subgroup is a matrix in HNF defining the subgroup of the ray class
group on the given generators gen.
The library syntax is rnfconductor(rnf,pol,prec)
.
(nf,pol,pr)
given a number field
nf
as output by nfinit
and a polynomial pol with
coefficients in nf
defining a relative extension L
of nf
,
evaluates the relative Dedekind criterion over the order defined by a
root of pol for the prime ideal pr and outputs a 3component
vector as the result. The first component is a flag equal to 1 if the
enlarged order could be proven to be prmaximal and to 0 otherwise (it
may be maximal in the latter case if pr is ramified in L
), the second
component is a pseudobasis of the enlarged order and the third component is
the valuation at pr of the order discriminant.
The library syntax is rnfdedekind(nf,pol,pr)
.
(nf,M)
given a pseudomatrix M
over the maximal
order of nf
, computes its pseudodeterminant.
The library syntax is rnfdet(nf,M)
.
(nf,pol)
given a number field nf
as
output by nfinit
and a polynomial pol with coefficients in
nf
defining a relative extension L
of nf
, computes
the relative
discriminant of L
. This is a twoelement row vector [D,d]
, where D
is
the relative ideal discriminant and d
is the relative discriminant
considered as an element of nf^*/{nf^*}^2
. The main variable of
nf
must be of lower priority than that of pol.
Note: As usual, nf
can be a bnf
as output by nfinit
.
The library syntax is rnfdiscf(bnf,pol)
.
(rnf,x)
rnf
being a relative
number field
extension L/K
as output by rnfinit
and x
being an element of L
expressed as a polynomial modulo the absolute equation rnf[11][1]
,
computes x
as an element of the relative extension L/K
as a polmod with
polmod coefficients.
The library syntax is rnfelementabstorel(rnf,x)
.
(rnf,x)
rnf
being a relative number
field extension L/K
as output by rnfinit
and x
being an element of
L
expressed as a polynomial or polmod with polmod coefficients, computes
x
as an element of K
as a polmod, assuming x
is in K
(otherwise an
error will occur). If x
is given on the relative integral basis, apply
rnfbasistoalg
first, otherwise PARI will believe you are dealing with a
vector.
The library syntax is rnfelementdown(rnf,x)
.
(rnf,x)
rnf
being a relative
number field extension L/K
as output by rnfinit
and x
being an
element of L
expressed as a polynomial or polmod with polmod
coefficients, computes x
as an element of the absolute extension L/Q
as
a polynomial modulo the absolute equation rnf[11][1]
. If x
is
given on the relative integral basis, apply rnfbasistoalg
first,
otherwise PARI will believe you are dealing with a vector.
The library syntax is rnfelementreltoabs(rnf,x)
.
(rnf,x)
rnf
being a relative number
field extension L/K
as output by rnfinit
and x
being an element of
K
expressed as a polynomial or polmod, computes x
as an element of the
absolute extension L/Q
as a polynomial modulo the absolute equation
rnf[11][1]
. Note that it is unnecessary to compute x
as an
element of the relative extension L/K
(its expression would be identical to
itself). If x
is given on the integral basis of K
, apply
nfbasistoalg
first, otherwise PARI will believe you are dealing with a
vector.
The library syntax is rnfelementup(rnf,x)
.
(nf,pol,{flag = 0})
given a number field
nf
as output by nfinit
(or simply a polynomial) and a
polynomial pol with coefficients in nf
defining a relative
extension L
of nf
, computes the absolute equation of L
over
Q.
If flag
is nonzero, outputs a 3component row vector [z,a,k]
, where
z
is the absolute equation of L
over Q, as in the default behaviour,
a
expresses as an element of L
a root alpha
of the polynomial
defining the base field nf
, and k
is a small integer such that
theta = beta+kalpha
where theta
is a root of z
and beta
a root
of pol
.
The main variable of nf
must be of lower priority than that
of pol. Note that for efficiency, this does not check whether the
relative equation is irreducible over nf
, but only if it is
squarefree. If it is reducible but squarefree, the result will be the
absolute equation of the étale algebra defined by pol. If pol
is not squarefree, an error message will be issued.
The library syntax is rnfequation0(nf,pol,flag)
.
(bnf,x)
given a big number field bnf
as output by bnfinit
, and either a polynomial x
with coefficients in
bnf
defining a relative extension L
of bnf
, or a
pseudobasis x
of such an extension, gives either a true bnf
basis
of L
in upper triangular Hermite normal form, if it exists,
zero otherwise.
The library syntax is rnfhermitebasis(nf,x)
.
(rnf,x)
rnf
being a relative
number field extension L/K
as output by rnfinit
and x
being an
ideal of the absolute extension L/Q
given in HNF
(if it is not, apply idealhnf
first), computes the relative pseudomatrix
in HNF giving the ideal x
considered as an ideal of the relative extension
L/K
.
The library syntax is rnfidealabstorel(rnf,x)
.
(rnf,x)
rnf
being a relative number
field extension L/K
as output by rnfinit
and x
being an ideal of
the absolute extension L/Q
given in HNF (if it is not, apply
idealhnf
first), gives the ideal of K
below x
, i.e. the
intersection of x
with K
. Note that, if x
is given as a relative ideal
(i.e. a pseudomatrix in HNF), then it is not necessary to use this function
since the result is simply the first ideal of the ideal list of the
pseudomatrix.
The library syntax is rnfidealdown(rnf,x)
.
(rnf,x)
rnf
being a relative number
field extension L/K
as output by rnfinit
and x
being a relative
ideal (which can be, as in the absolute case, of many different types,
including of course elements), computes as a 2component row vector the
relative Hermite normal form of x
, the first component being the HNF matrix
(with entries on the integral basis), and the second component the ideals.
The library syntax is rnfidealhermite(rnf,x)
.
(rnf,x,y)
rnf
being a relative number
field extension L/K
as output by rnfinit
and x
and y
being ideals
of the relative extension L/K
given by pseudomatrices, outputs the ideal
product, again as a relative ideal.
The library syntax is rnfidealmul(rnf,x,y)
.
(rnf,x)
rnf
being a relative
number field extension L/K
as output by rnfinit
and x
being a
relative ideal (which can be, as in the absolute case, of many different
types, including of course elements), computes the norm of the ideal x
considered as an ideal of the absolute extension L/Q
. This is identical to
idealnorm(rnfidealnormrel(rnf,x))
, only faster.
The library syntax is rnfidealnormabs(rnf,x)
.
(rnf,x)
rnf
being a relative
number field
extension L/K
as output by rnfinit
and x
being a relative ideal
(which can be, as in the absolute case, of many different types, including
of course elements), computes the relative norm of x
as a ideal of K
in HNF.
The library syntax is rnfidealnormrel(rnf,x)
.
(rnf,x)
rnf
being a relative
number field
extension L/K
as output by rnfinit
and x
being a relative ideal
(which can be, as in the absolute case, of many different types, including
of course elements), computes the HNF matrix of the ideal x
considered
as an ideal of the absolute extension L/Q
.
The library syntax is rnfidealreltoabs(rnf,x)
.
(rnf,x)
rnf
being a relative
number field
extension L/K
as output by rnfinit
and x
being an ideal of the
relative extension L/K
given by a pseudomatrix, gives a vector of
two generators of x
over Z_L
expressed as polmods with polmod
coefficients.
The library syntax is rnfidealtwoelement(rnf,x)
.
(rnf,x)
rnf
being a relative number
field
extension L/K
as output by rnfinit
and x
being an ideal of
K
, gives the ideal xZ_L
as an absolute ideal of L/Q
(the relative
ideal representation is trivial: the matrix is the identity matrix, and
the ideal list starts with x
, all the other ideals being Z_K
).
The library syntax is rnfidealup(rnf,x)
.
(nf,pol)
nf
being a number field in
nfinit
format considered as base field, and pol a polynomial defining a relative
extension over nf
, this computes all the necessary data to work in the
relative extension. The main variable of pol must be of higher priority
(i.e. lower number) than that of nf
, and the coefficients of pol
must be in nf
.
The result is an 11component row vector as follows (most of the components
are technical), the numbering being very close to that of nfinit
. In
the following description, we let K
be the base field defined by
nf
, m
the degree of the base field, n
the relative degree, L
the large field (of relative degree n
or absolute degree nm
), r_1
and
r_2
the number of real and complex places of K
.
rnf[1]
contains the relative polynomial pol.
rnf[2]
is a row vector with r_1+r_2
entries, entry j
being
a 2component row vector [r_{j,1},r_{j,2}]
where r_{j,1}
and r_{j,2}
are the number of real and complex places of L
above the j
th place of
K
so that r_{j,1} = 0
and r_{j,2} = n
if j
is a complex place, while if
j
is a real place we have r_{j,1}+2r_{j,2} = n
.
rnf[3]
is a twocomponent row vector [d(L/K),s]
where d(L/K)
is the relative ideal discriminant of L/K
and s
is the discriminant of
L/K
viewed as an element of K^*/(K^*)^2
, in other words it is the output
of rnfdisc
.
rnf[4]
is the ideal index f
, i.e. such that
d(pol)Z_K = f^2d(L/K)
.
rnf[5]
is a vector vm with 7 entries useful for certain
computations in the relative extension L/K
. vm[1]
is a vector of
r_1+r_2
matrices, the j
th matrix being an (r_{1,j}+r_{2,j}) x n
matrix M_j
representing the numerical values of the conjugates of the
j
th embedding of the elements of the integral basis, where r_{i,j}
is as
in rnf[2]
. vm[2]
is a vector of r_1+r_2
matrices, the
j
th matrix MC_j
being essentially the conjugate of the matrix M_j
except that the last r_{2,j}
columns are also multiplied by 2.
vm[3]
is a vector of r_1+r_2
matrices T2_j
, where T2_j
is
an n x n
matrix equal to the real part of the product MC_j.M_j
(which is a real positive definite matrix). vm[4]
is the n x n
matrix T
whose entries are the relative traces of omega_iomega_j
expressed as polmods in nf
, where the omega_i
are the elements
of the relative integral basis. Note that the j
th embedding of T
is
equal to \overline{MC_j}.M_j
, and in particular will be equal to
T2_j
if r_{2,j} = 0
. Note also that the relative ideal discriminant of
L/K
is equal to det (T)
times the square of the product of the ideals
in the relative pseudobasis (in rnf[7][2]
). The last 3 entries
vm[5]
, vm[6]
and vm[7]
are linked to the different
as in nfinit
, but have not yet been implemented.
rnf[6]
is a row vector with r_1+r_2
entries, the j
th entry
being the
row vector with r_{1,j}+r_{2,j}
entries of the roots of the j
th embedding
of the relative polynomial pol.
rnf[7]
is a twocomponent row vector, where the first component is
the relative integral pseudo basis expressed as polynomials (in the variable of
pol
) with polmod coefficients in nf
, and the second component is the
ideal list of the pseudobasis in HNF.
rnf[8]
is the inverse matrix of the integral basis matrix, with
coefficients polmods in nf
.
rnf[9]
may be the multiplication table of the integral basis, but
is not implemented at present.
rnf[10]
is nf
.
rnf[11]
is a vector vabs with 5 entries describing the
absolute extension L/Q
. vabs[1]
is an absolute equation.
vabs[2]
expresses the generator alpha
of the number field
nf
as a polynomial modulo the absolute equation vabs[1]
.
vabs[3]
is a small integer k
such that, if beta
is an abstract
root of pol and alpha
the generator of nf
, the generator
whose root is vabs will be beta + k alpha
. Note that one must
be very careful if k ! = 0
when dealing simultaneously with absolute and
relative quantities since the generator chosen for the absolute extension
is not the same as for the relative one. If this happens, one can of course
go on working, but we strongly advise to change the relative polynomial so
that its root will be beta + k alpha
. Typically, the GP instruction would
be
pol = subst(pol, x, x  k*Mod(y,nf.pol))
Finally, vabs[4]
is the absolute integral basis of L
expressed in HNF
(hence as would be output by nfinit(vabs[1])
), and vabs[5]
the
inverse matrix of the integral basis, allowing to go from polmod to integral
basis representation.
The library syntax is rnfinitalg(nf,pol,prec)
.
(bnf,x)
given a big number field bnf
as
output by bnfinit
, and either a polynomial x
with coefficients in
bnf
defining a relative extension L
of bnf
, or a
pseudobasis x
of such an extension, returns true (1) if L/bnf
is
free, false (0) if not.
The library syntax is rnfisfree(bnf,x)
, and the result is a long
.
(bnf,ext,el,{flag = 1})
similar to
bnfisnorm
but in the relative case. This tries to decide whether the
element el in bnf is the norm of some y
in ext.
bnf
is as output by bnfinit
.
ext
is a relative extension which has to be a row vector whose
components are:
ext[1]
: a relative equation of the number field ext over
bnf. As usual, the priority of the variable of the polynomial
defining the ground field bnf (say y
) must be lower than the
main variable of ext[1]
, say x
.
ext[2]
: the generator y
of the base field as a polynomial in x
(as
given by rnfequation
with flag = 1
).
ext[3]
: is the bnfinit
of the absolute extension ext/Q
.
This returns a vector [a,b]
, where el = Norm(a)*b
. It looks for a
solution which is an S
integer, with S
a list of places (of bnf)
containing the ramified primes, the generators of the class group of
ext, as well as those primes dividing el. If ext/bnf
is known to be Galois, set flag = 0
(here el is a norm iff b = 1
).
If flag
is non zero add to S
all the places above the primes which: divide
flag
if flag < 0
, or are less than flag
if flag > 0
. The answer is guaranteed
(i.e. el is a norm iff b = 1
) under GRH, if S
contains all
primes less than 12 log ^2disc(Ext)
, where
Ext is the normal closure of ext / bnf
. Example:
bnf = bnfinit(y^3 + y^2  2*y  1); p = x^2 + Mod(y^2 + 2*y + 1, bnf.pol); rnf = rnfequation(bnf,p,1); ext = [p, rnf[2], bnfinit(rnf[1])]; rnfisnorm(bnf,ext,17, 1)
checks whether 17
is a norm in the Galois extension Q(beta) /
B<I<Q>>(F<alpha>)
, where alpha^3 + alpha^2  2alpha  1 = 0
and beta^2 +
F<alpha>^2 + 2*F<alpha> + 1 = 0
(it is).
The library syntax is rnfisnorm(bnf,ext,x,flag,prec)
.
(bnr,subgroup,{deg = 0})
bnr
being as output by bnrinit
, finds a relative equation for the
class field corresponding to the module in bnr and the given
congruence subgroup. If deg is positive, outputs the list of all
relative equations of degree deg contained in the ray class field
defined by bnr.
(THIS PROGRAM IS STILL IN DEVELOPMENT STAGE)
The library syntax is rnfkummer(bnr,subgroup,deg,prec)
,
where deg is a long
.
(nf,pol,order)
given a polynomial
pol with coefficients in nf and an order order as output
by rnfpseudobasis
or similar, gives [[neworder],U]
, where
neworder is a reduced order and U
is the unimodular transformation
matrix.
The library syntax is rnflllgram(nf,pol,order,prec)
.
(bnr,pol)
bnr being a big ray
class field as output by bnrinit
and pol a relative polynomial
defining an Abelian extension, computes the norm group (alias Artin
or Takagi group) corresponding to the Abelian extension of bnf = bnr[1]
defined by pol, where the module corresponding to bnr is assumed
to be a multiple of the conductor (i.e. polrel defines a subextension of
bnr). The result is the HNF defining the norm group on the given generators
of bnr[5][3]
. Note that neither the fact that pol defines an
Abelian extension nor the fact that the module is a multiple of the conductor
is checked. The result is undefined if the assumption is not correct.
The library syntax is rnfnormgroup(bnr,pol)
.
(nf,pol)
relative version of polred
.
Given a monic polynomial pol with coefficients in nf
, finds a
list of relative polynomials defining some subfields, hopefully simpler and
containing the original field. In the present version 2.2.0, this is slower
than rnfpolredabs
.
The library syntax is rnfpolred(nf,pol,prec)
.
(nf,pol,{flag = 0})
relative version of
polredabs
. Given a monic polynomial pol with coefficients in
nf
, finds a simpler relative polynomial defining the same field. If
flag = 1
, returns [P,a]
where P
is the default output and a
is an
element expressed on a root of P
whose characteristic polynomial is
pol, if flag = 2
, returns an absolute polynomial (same as
rnfequation(nf,rnfpolredabs(nf,pol))
but faster).
Remark. In the present implementation, this is both faster and
much more efficient than rnfpolred
, the difference being more
dramatic than in the absolute case. This is because the implementation of
rnfpolred
is based on (a partial implementation of) an incomplete
reduction theory of lattices over number fields (i.e. the function
rnflllgram
) which deserves to be improved.
The library syntax is rnfpolredabs(nf,pol,flag,prec)
.
(nf,pol)
given a number field
nf
as output by nfinit
and a polynomial pol with
coefficients in nf
defining a relative extension L
of nf
,
computes a pseudobasis (A,I)
and the relative discriminant of L
.
This is output as
a fourelement row vector [A,I,D,d]
, where D
is the relative ideal
discriminant and d
is the relative discriminant considered as an element of
nf^*/{nf^*}^2
.
Note: As usual, nf
can be a bnf
as output by bnfinit
.
The library syntax is rnfpseudobasis(nf,pol)
.
(nf,x)
given a number field nf
as
output by nfinit
and either a polynomial x
with coefficients in
nf
defining a relative extension L
of nf
, or a pseudobasis
x
of such an extension as output for example by rnfpseudobasis
,
computes another pseudobasis (A,I)
(not in HNF in general) such that all
the ideals of I
except perhaps the last one are equal to the ring of
integers of nf
, and outputs the fourcomponent row vector [A,I,D,d]
as in rnfpseudobasis
. The name of this function comes from the fact
that the ideal class of the last ideal of I
(which is well defined) is
called the Steinitz class of the module Z_L
.
Note: nf
can be a bnf
as output by bnfinit
.
The library syntax is rnfsteinitz(nf,x)
.
(bnr,{bound},{flag = 0})
bnr being as output by bnrinit
or a list of cyclic components
of a finite Abelian group G
, outputs the list of subgroups of G
(of index bounded by bound, if not omitted). Subgroups are given
as HNF left divisors of the
SNF matrix corresponding to G
. If flag = 0
(default) and bnr is as output by
bnrinit
, gives only the subgroups whose modulus is the conductor.
The library syntax is subgrouplist0(bnr,bound,flag,prec)
, where
bound, flag
and prec
are long integers.
(znf,x,{flag = 0})
znf being a number
field initialized by zetakinit
(not by nfinit
),
computes the value of the Dedekind zeta function of the number
field at the complex number x
. If flag = 1
computes Dedekind Lambda
function instead (i.e. the product of the
Dedekind zeta function by its gamma and exponential factors).
The accuracy of the result depends in an essential way on the accuracy of
both the zetakinit
program and the current accuracy, but even so the
result may be off by up to 5 or 10 decimal digits.
The library syntax is glambdak(znf,x,prec)
or
gzetak(znf,x,prec)
.
(x)
computes a number of initialization data
concerning the number field defined by the polynomial x
so as to be able
to compute the Dedekind zeta and lambda functions (respectively
zetak(x)
and zetak(x,1)
). This function calls in particular
the bnfinit
program. The result is a 9component vector v
whose
components are very technical and cannot really be used by the user except
through the zetak
function. The only component which can be used if
it has not been computed already is v[1][4]
which is the result of the
bnfinit
call.
This function is very inefficient and should be rewritten. It needs to
computes millions of coefficients of the corresponding Dirichlet series if
the precision is big. Unless the discriminant is small it will not be able
to handle more than 9 digits of relative precision
(e.g zetakinit(x^8  2)
needs 440MB of memory at default
precision).
The library syntax is initzeta(x)
.
We group here all functions which are specific to polynomials or power series. Many other functions which can be applied on these objects are described in the other sections. Also, some of the functions described here can be applied to other types.
(a
^
b)
p
adic (if a
is an integer greater or
equal to 2) or power series zero (in all other cases), with precision given
by b
.
The library syntax is ggrandocp(a,b)
, where b
is a long
.
(x,{v})
derivative of x
with respect to the main
variable if v
is omitted, and with respect to v
otherwise. x
can be any
type except polmod. The derivative of a scalar type is zero, and the
derivative of a vector or matrix is done componentwise. One can use x'
as a
shortcut if the derivative is with respect to the main variable of x
.
The library syntax is deriv(x,v)
, where v
is a long
, and an omitted v
is coded as
1
.
(x)
replaces in x
the formal variables by the values that
have been assigned to them after the creation of x
. This is mainly useful
in GP, and not in library mode. Do not confuse this with substitution (see
subst
). Applying this function to a character string yields the
output from the corresponding GP command, as if directly input from the
keyboard (see Label se:strings).
The library syntax is geval(x)
. The more basic functions poleval(q,x)
,
qfeval(q,x)
, and hqfeval(q,x)
evaluate q
at x
, where q
is respectively assumed to be a polynomial, a quadratic form (a symmetric
matrix), or an Hermitian form (an Hermitian complex matrix).
(pol,p,r,{flag = 0})
p
adic factorization
of the polynomial pol to precision r
, the result being a
twocolumn matrix as in factor
. The factors are normalized so that
their leading coefficient is a power of p
. r
must be strictly larger than
the p
adic valuation of the discriminant of pol for the result to
make any sense. The method used is a modified version of the round 4
algorithm of Zassenhaus.
If flag = 1
, use an algorithm due to Buchmann and Lenstra, which is
usually less efficient.
The library syntax is factorpadic4(pol,p,r)
, where r
is a long
integer.
(x,{v})
formal integration of x
with
respect to the main variable if v
is omitted, with respect to the variable
v
otherwise. Since PARI does not know about ``abstract'' logarithms (they
are immediately evaluated, if only to a power series), logarithmic terms in
the result will yield an error. x
can be of any type. When x
is a
rational function, it is assumed that the base ring is an integral domain of
characteristic zero.
The library syntax is integ(x,v)
, where v
is a long
and an omitted v
is coded
as 1
.
(pol,a)
vector of p
adic roots of the
polynomial
pol
congruent to the p
adic number a
modulo p
(or modulo 4 if p = 2
),
and with the same p
adic precision as a
. The number a
can be an
ordinary p
adic number (type t_PADIC
, i.e. an element of Q_p
) or
can be an element of a finite extension of Q_p
, in which case it is of
type t_POLMOD
, where at least one of the coefficients of the polmod is a
p
adic number. In this case, the result is the vector of roots belonging to
the same extension of Q_p
as a
.
The library syntax is apprgen9(pol,a)
, but if a
is known to be simply a p
adic number
(type t_PADIC
), the syntax apprgen(pol,a)
can be used.
(x,s,{v})
coefficient of degree s
of the
polynomial x
, with respect to the main variable if v
is omitted, with
respect to v
otherwise.
The library syntax is polcoeff0(x,s,v)
, where v
is a long
and an omitted v
is coded
as 1
. Also available is truecoeff(x,v)
.
(x,{v})
degree of the polynomial x
in the main
variable if v
is omitted, in the variable v
otherwise. This is to be
understood as follows. When x
is a polynomial or a rational function, it
gives the degree of x
, the degree of 0
being 1
by convention. When x
is a nonzero scalar, it gives 0, and when x
is a zero scalar, it gives
1
. Return an error otherwise.
The library syntax is poldegree(x,v)
, where v
and the result are long
s (and an
omitted v
is coded as 1
). Also available is degree(x)
, which is
equivalent to poldegree(x,1)
.
(n,{v = x})
n
th cyclotomic polynomial, in variable
v
(x
by default). The integer n
must be positive.
The library syntax is cyclo(n,v)
, where n
and v
are long
integers (v
is a variable number, usually obtained through varn
).
(pol,{v})
discriminant of the polynomial
pol in the main variable is v
is omitted, in v
otherwise. The
algorithm used is the subresultant algorithm.
The library syntax is poldisc0(x,v)
. Also available is discsr(x)
, equivalent
to poldisc0(x,1)
.
(f)
reduced discriminant vector of the
(integral, monic) polynomial f
. This is the vector of elementary divisors
of Z[alpha]/f'(alpha)Z[alpha]
, where alpha
is a root of the
polynomial f
. The components of the result are all positive, and their
product is equal to the absolute value of the discriminant of f
.
The library syntax is reduceddiscsmith(x)
.
(x, y, p, e)
given a vector y
of
polynomials that are pairwise relatively prime modulo the prime p
,
and whose product is congruent to x
modulo p
, lift the elements of
y
to polynomials whose product is congruent to x
modulo p^e
.
The library syntax is polhensellift(x,y,p,e)
where e
must be a long
.
(xa,{ya},{v = x},{&e})
given the data vectors
xa
and ya
of the same length n
(xa
containing the x
coordinates,
and ya
the corresponding y
coordinates), this function finds the
interpolating polynomial passing through these points and evaluates it
at v
. If ya
is omitted, return the polynomial interpolating the
(i,xa[i])
. If present, e
will contain an error estimate on the returned
value.
The library syntax is polint(xa,ya,v,&e)
, where e
will contain an error estimate on the
returned value.
(pol)
pol being a polynomial (univariate in the present version 2.2.0), returns 1 if pol is nonconstant and irreducible, 0 otherwise. Irreducibility is checked over the smallest base field over which pol seems to be defined.
The library syntax is gisirreducible(pol)
.
(x,{v})
leading coefficient of the polynomial or
power series x
. This is computed with respect to the main variable of x
if v
is omitted, with respect to the variable v
otherwise.
The library syntax is pollead(x,v)
, where v
is a long
and an omitted v
is coded as
1
. Also available is leadingcoeff(x)
.
(n,{v = x})
creates the n^{th}
Legendre polynomial, in variable v
.
The library syntax is legendre(n)
, where x
is a long
.
(pol)
reciprocal polynomial of pol, i.e. the coefficients are in reverse order. pol must be a polynomial.
The library syntax is polrecip(x)
.
(x,y,{v},{flag = 0})
resultant of the two
polynomials x
and y
with exact entries, with respect to the main
variables of x
and y
if v
is omitted, with respect to the variable v
otherwise. The algorithm used is the subresultant algorithm by default.
If flag = 1
, uses the determinant of Sylvester's matrix instead (here x
and
y
may have nonexact coefficients).
If flag = 2
, uses Ducos's modified subresultant algorithm. It should be much
faster than the default if the coefficient ring is complicated (e.g
multivariate polynomials or huge coefficients), and slightly slower
otherwise.
The library syntax is polresultant0(x,y,v,flag)
, where v
is a long
and an omitted v
is coded as 1
. Also available are subres(x,y)
(flag = 0
) and
resultant2(x,y)
(flag = 1
).
(pol,{flag = 0})
complex roots of the polynomial
pol, given as a column vector where each root is repeated according to
its multiplicity. The precision is given as for transcendental functions: under
GP it is kept in the variable realprecision
and is transparent to the
user, but it must be explicitly given as a second argument in library mode.
The algorithm used is a modification of A. nhage>Schönhage's remarkable rootfinding algorithm, due to and implemented by X. Gourdon. Barring bugs, it is guaranteed to converge and to give the roots to the required accuracy.
If flag = 1
, use a variant of the NewtonRaphson method, which is not
guaranteed to converge, but is rather fast. If you get the messages ``too
many iterations in roots'' or ``INTERNAL ERROR: incorrect result in roots'',
use the default function (i.e. no flag or flag = 0
). This used to be the
default rootfinding function in PARI until version 1.39.06.
The library syntax is roots(pol,prec)
or rootsold(pol,prec)
.
(pol,p,{flag = 0})
row vector of roots modulo
p
of the polynomial pol. The particular nonprime value p = 4
is
accepted, mainly for 2
adic computations. Multiple roots are not
repeated.
If p < 100
, you may try setting flag = 1
, which uses a naive search. In this
case, multiple roots are repeated with their order of multiplicity.
The library syntax is rootmod(pol,p)
(flag = 0
) or
rootmod2(pol,p)
(flag = 1
).
(pol,p,r)
row vector of p
adic roots of the
polynomial pol with p
adic precision equal to r
. Multiple roots are
not repeated. p
is assumed to be a prime.
The library syntax is rootpadic(pol,p,r)
, where r
is a long
.
(pol,{a},{b})
number of real roots of the real
polynomial pol in the interval ]a,b]
, using Sturm's algorithm. a
(resp. b
) is taken to be  oo
(resp. + oo
) if omitted.
The library syntax is sturmpart(pol,a,b)
. Use NULL
to omit an argument.
sturm(pol)
is equivalent to
sturmpart(pol,NULL,NULL)
. The result is a long
.
(n,d,{v = x})
gives a polynomial (in variable
v
) defining the subAbelian extension of degree d
of the cyclotomic
field Q(zeta_n)
, where d  phi(n)
. (Z/nZ)^*
has to be cyclic
(i.e. n = 2
, 4
, p^k
or 2p^k
for an odd prime p
). The function
galoissubcyclo
covers the general case.
The library syntax is subcyclo(n,d,v)
, where v
is a variable number.
(x,y)
forms the Sylvester matrix
corresponding to the two polynomials x
and y
, where the coefficients of
the polynomials are put in the columns of the matrix (which is the natural
direction for solving equations afterwards). The use of this matrix can be
essential when dealing with polynomials with inexact entries, since
polynomial Euclidean division doesn't make much sense in this case.
The library syntax is sylvestermatrix(x,y)
.
(x,n)
creates the vector of the symmetric powers
of the roots of the polynomial x
up to power n
, using Newton's
formula.
The library syntax is polsym(x)
.
(n,{v = x})
creates the n^{th}
Chebyshev polynomial, in variable v
.
The library syntax is tchebi(n,v)
, where n
and v
are long
integers (v
is a variable number).
(n,m)
creates Zagier's polynomial P_{n,m}
used in
the functions sumalt
and sumpos
(with flag = 1
). The exact
definition can be found in a forthcoming paper. One must have m <= n
.
The library syntax is polzagreel(n,m,prec)
if the result is only wanted as a polynomial
with real coefficients to the precision prec
, or polzag(n,m)
if the result is wanted exactly, where n
and m
are long
s.
(x,y)
convolution (or Hadamard product) of the
two power series x
and y
; in other words if x = sum a_k*X^k
and y = sum
b_k*X^k
then serconvol(x,y) = sum a_k*b_k*X^k
.
The library syntax is convol(x,y)
.
(x)
x
must be a power series with only
nonnegative exponents. If x = sum (a_k/k!)*X^k
then the result is sum
a_k*X^k
.
The library syntax is laplace(x)
.
(x)
reverse power series (i.e. x^{1}
, not 1/x
)
of x
. x
must be a power series whose valuation is exactly equal to one.
The library syntax is recip(x)
.
(x,y,z)
replace the simple variable y
by the argument z
in the ``polynomial''
expression x
. Every type is allowed for x
, but if it is not a genuine
polynomial (or power series, or rational function), the substitution will be
done as if the scalar components were polynomials of degree one. In
particular, beware that:
? subst(1, x, [1,2; 3,4]) %1 = [1 0]
[0 1]
? subst(1, x, Mat([0,1])) *** forbidden substitution by a non square matrix
If x
is a power series, z
must be either a polynomial, a power series, or
a rational function. y
must be a simple variable name.
The library syntax is gsubst(x,v,z)
, where v
is the number of
the variable y
.
(x,y)
Taylor expansion around 0
of x
with respect
to
the simple variable y
. x
can be of any reasonable type, for example a
rational function. The number of terms of the expansion is transparent to the
user under GP, but must be given as a second argument in library mode.
The library syntax is tayl(x,y,n)
, where the long
integer n
is the desired number of
terms in the expansion.
(tnf,a,{sol})
solves the equation
P(x,y) = a
in integers x
and y
, where tnf was created with
thueinit(P)
. sol, if present, contains the solutions of
Norm(x) = a
modulo units of positive norm in the number field
defined by P
(as computed by bnfisintnorm
). If tnf was
computed without assuming GRH (flag = 1
in thueinit
), the
result is unconditional. For instance, here's how to solve the Thue
equation x^{13}  5y^{13} =  4
:
? tnf = thueinit(x^13  5); ? thue(tnf, 4) %1 = [[1, 1]]
Hence, assuming GRH, the only solution is x = 1
, y = 1
.
The library syntax is thue(tnf,a,sol)
, where an omitted sol is coded
as NULL
.
(P,{flag = 0})
initializes the tnf
corresponding to P
. It is meant to be used in conjunction with thue
to solve Thue equations P(x,y) = a
, where a
is an integer. If flag
is
nonzero, certify the result unconditionnaly, Otherwise, assume GRH,
this being much faster of course.
The library syntax is thueinit(P,flag,prec)
.
Note that most linear algebra functions operating on subspaces defined by
generating sets (such as mathnf
, qflll
, etc.) take matrices as
arguments. As usual, the generating vectors are taken to be the
columns of the given matrix.
(x,k,{flag = 0})
x
being
real, complex, or p
adic, finds a polynomial of degree at most k
with
integer coefficients having x
as approximate root. Note that the polynomial
which is obtained is not necessarily the ``correct'' one (it's not even
guaranteed to be irreducible!). One can check the closeness either by a
polynomial evaluation or substitution, or by computing the roots of the
polynomial given by algdep.
If x
is padic, flag
is meaningless and the algorithm LLLreduces the
``dual lattice'' corresponding to the powers of x
.
Otherwise, if flag
is zero, the algorithm used is a variant of the LLL
algorithm due to Hastad, Lagarias and Schnorr (STACS 1986). If the precision
is too low, the routine may enter an infinite loop.
If flag
is nonzero, use a standard LLL. flag
then indicates a precision,
which should be between 0.5
and 1.0
times the number of decimal digits
to which x
was computed.
The library syntax is algdep0(x,k,flag,prec)
, where k
and flag
are long
s.
Also available is algdep(x,k,prec)
(flag = 0
).
(A,{v = x},{flag = 0})
characteristic polynomial
of A
with respect to the variable v
, i.e. determinant of v*IA
if A
is a square matrix, determinant of the map ``multiplication by A
'' if A
is a scalar, in particular a polmod (e.g. charpoly(I,x) = x^2+1
).
Note that in the latter case, the minimal polynomial can be obtained
as
minpoly(A)= { local(y); y = charpoly(A); y / gcd(y,y') }
The value of flag
is only significant for matrices.
If flag = 0
, the method used is essentially the same as for computing the
adjoint matrix, i.e. computing the traces of the powers of A
.
If flag = 1
, uses Lagrange interpolation which is almost always slower.
If flag = 2
, uses the Hessenberg form. This is faster than the default when
the coefficients are integermod a prime or real numbers, but is usually
slower in other base rings.
The library syntax is charpoly0(A,v,flag)
, where v
is the variable number. Also available
are the functions caract(A,v)
(flag = 1
), carhess(A,v)
(flag = 2
), and caradj(A,v,pt)
where, in this last case,
pt is a GEN*
which, if not equal to NULL
, will receive
the address of the adjoint matrix of A
(see matadjoint
), so both
can be obtained at once.
(x,{y})
concatenation of x
and y
. If x
or y
is
not a vector or matrix, it is considered as a onedimensional vector. All
types are allowed for x
and y
, but the sizes must be compatible. Note
that matrices are concatenated horizontally, i.e. the number of rows stays
the same. Using transpositions, it is easy to concatenate them vertically.
To concatenate vectors sideways (i.e. to obtain a tworow or twocolumn
matrix), first transform the vector into a onerow or onecolumn matrix using
the function Mat
. Concatenating a row vector to a matrix having the
same number of columns will add the row to the matrix (top row if the vector
is x
, i.e. comes first, and bottom row otherwise).
The empty matrix [;]
is considered to have a number of rows compatible
with any operation, in particular concatenation. (Note that this is
definitely not the case for empty vectors [ ]
or [ ]~
.)
If y
is omitted, x
has to be a row vector or a list, in which case its
elements are concatenated, from left to right, using the above rules.
? concat([1,2], [3,4]) %1 = [1, 2, 3, 4] ? a = [[1,2]~, [3,4]~]; concat(a) %2 = [1, 2, 3, 4]~ ? a[1] = Mat(a[1]); concat(a) %3 = [1 3]
[2 4]
? concat([1,2; 3,4], [5,6]~) %4 = [1 2 5]
[3 4 6] ? concat([%, [7,8]~, [1,2,3,4]]) %5 = [1 2 5 7]
[3 4 6 8]
[1 2 3 4]
The library syntax is concat(x,y)
.
(x,{flag = 0})
x
being a
vector with real or complex coefficients, finds a small integral linear
combination among these coefficients.
If flag = 0
, uses a variant of the LLL algorithm due to Hastad, Lagarias
and Schnorr (STACS 1986).
If flag > 0
, uses the LLL algorithm. flag
is a parameter which should be
between one half the number of decimal digits of precision and that number
(see algdep
).
If flag < 0
, returns as soon as one relation has been found.
The library syntax is lindep0(x,flag,prec)
. Also available is
lindep(x,prec)
(flag = 0
).
(n)
creates an empty list of maximal length n
.
This function is useless in library mode.
(list,x,n)
inserts the object x
at
position n
in list (which must be of type t_LIST
). All the
remaining elements of list (from position n+1
onwards) are shifted
to the right. This and listput
are the only commands which enable
you to increase a list's effective length (as long as it remains under
the maximal length specified at the time of the listcreate
).
This function is useless in library mode.
(list)
kill list. This deletes all
elements from list and sets its effective length to 0
. The maximal
length is not affected.
This function is useless in library mode.
(list,x,{n})
sets the n
th element of the list
list (which must be of type t_LIST
) equal to x
. If n
is omitted,
or greater than the list current effective length, just appends x
. This and
listinsert
are the only commands which enable you to increase a list's
effective length (as long as it remains under the maximal length specified at
the time of the listcreate
).
If you want to put an element into an occupied cell, i.e. if you don't want to
change the effective length, you can consider the list as a vector and use
the usual list[n] = x
construct.
This function is useless in library mode.
(list,{flag = 0})
sorts list (which must
be of type t_LIST
) in place. If flag
is nonzero, suppresses all repeated
coefficients. This is much faster than the vecsort
command since no
copy has to be made.
This function is useless in library mode.
(x)
adjoint matrix of x
, i.e. the matrix y
of cofactors of x
, satisfying x*y = det (x)*Id
. x
must be a
(nonnecessarily invertible) square matrix.
The library syntax is adj(x)
.
(x)
the left companion matrix to the polynomial x
.
The library syntax is assmat(x)
.
(x,{flag = 0})
determinant of x
. x
must be a
square matrix.
If flag = 0
, uses GaussBareiss.
If flag = 1
, uses classical Gaussian elimination, which is better when the
entries of the matrix are reals or integers for example, but usually much
worse for more complicated entries like multivariate polynomials.
The library syntax is det(x)
(flag = 0
) and det2(x)
(flag = 1
).
(x)
x
being an m x n
matrix with integer
coefficients, this function computes a multiple of the determinant of the
lattice generated by the columns of x
if it is of rank m
, and returns
zero otherwise. This function can be useful in conjunction with the function
mathnfmod
which needs to know such a multiple. Other ways to obtain
this determinant (assuming the rank is maximal) is
matdet(qflll(x,4)[2]*x)
or more simply matdet(mathnf(x))
.
Experiment to see which is faster for your applications.
The library syntax is detint(x)
.
(x)
x
being a vector, creates the diagonal matrix
whose diagonal entries are those of x
.
The library syntax is diagonal(x)
.
(x)
gives the eigenvectors of x
as columns of a
matrix.
The library syntax is eigen(x)
.
(x)
Hessenberg form of the square matrix x
.
The library syntax is hess(x)
.
(x)
x
being a long
, creates the Hilbert
matrix of order x
, i.e. the matrix whose coefficient (i
,j
) is 1/
(i+j1)
.
The library syntax is mathilbert(x)
.
(x,{flag = 0})
if x
is a (not necessarily square)
matrix of maximal rank, finds the upper triangular
Hermite normal form of x
. If the rank of x
is equal to its number
of rows, the result is a square matrix. In general, the columns of the
result form a basis of the lattice spanned by the columns of x
.
If flag = 0
, uses the naive algorithm. If the Zmodule generated by the
columns is a lattice, it is recommanded to use
mathnfmod(x, matdetint(x))
instead (much faster).
If flag = 1
, uses Batut's algorithm. Outputs a twocomponent row vector
[H,U]
, where H
is the upper triangular Hermite normal form
of x
(i.e. the default result) and U
is the unimodular transformation
matrix such that xU = [0H]
. If the rank of x
is equal to its number of
rows, H
is a square matrix. In general, the columns of H
form a basis
of the lattice spanned by the columns of x
.
If flag = 2
, uses Havas's algorithm. Outputs [H,U,P]
, such that
H
and U
are as before and P
is a permutation of the rows such that P
applied to xU
gives H
. This does not work very well in present version
2.2.0.
If flag = 3
, uses Batut's algorithm, and outputs [H,U,P]
as in the previous
case.
If flag = 4
, as in case 1 above, but uses LLL reduction along the way.
The library syntax is mathnf0(x,flag)
. Also available are hnf(x)
(flag = 0
) and
hnfall(x)
(flag = 1
). To reduce huge (say 400 x 400
and
more) relation matrices (sparse with small entries), you can use the pair
hnfspec
/ hnfadd
. Since this is rather technical and the
calling interface may change, they are not documented yet. Look at the code
in basemath/alglin1.c
.
(x,d)
if x
is a (not necessarily square) matrix of
maximal rank with integer entries, and d
is a multiple of the (nonzero)
determinant of the lattice spanned by the columns of x
, finds the
upper triangular Hermite normal form of x
.
If the rank of x
is equal to its number of rows, the result is a square
matrix. In general, the columns of the result form a basis of the lattice
spanned by the columns of x
. This is much faster than mathnf
when d
is known.
The library syntax is hnfmod(x,d)
.
(x,d)
outputs the (upper triangular)
Hermite normal form of x
concatenated with d
times
the identity matrix.
The library syntax is hnfmodid(x,d)
.
(n)
creates the n x n
identity matrix.
The library syntax is idmat(n)
where n
is a long
.
Related functions are gscalmat(x,n)
, which creates x
times the
identity matrix (x
being a GEN
and n
a long
), and
gscalsmat(x,n)
which is the same when x
is a long
.
(x,{flag = 0})
gives a basis for the image of the
matrix x
as columns of a matrix. A priori the matrix can have entries of
any type. If flag = 0
, use standard Gauss pivot. If flag = 1
, use
matsupplement
.
The library syntax is matimage0(x,flag)
. Also available is image(x)
(flag = 0
).
(x)
gives the vector of the column indices which
are not extracted by the function matimage
. Hence the number of
components of matimagecompl(x)
plus the number of columns of
matimage(x)
is equal to the number of columns of the matrix x
.
The library syntax is imagecompl(x)
.
(x)
x
being a matrix of rank r
, gives two
vectors y
and z
of length r
giving a list of rows and columns
respectively (starting from 1) such that the extracted matrix obtained from
these two vectors using vecextract(x,y,z)
is invertible.
The library syntax is indexrank(x)
.
(x,y)
x
and y
being two matrices with the same
number of rows each of whose columns are independent, finds a basis of the
Qvector space equal to the intersection of the spaces spanned by the
columns of x
and y
respectively. See also the function
idealintersect
, which does the same for free Zmodules.
The library syntax is intersect(x,y)
.
(x,y)
gives a column vector belonging to the
inverse image of the column vector y
by the matrix x
if one exists, the
empty vector otherwise. To get the complete inverse image, it suffices to add
to the result any element of the kernel of x
obtained for example by
matker
.
The library syntax is inverseimage(x,y)
.
(x)
returns true (1) if x
is a diagonal matrix,
false (0) if not.
The library syntax is isdiagonal(x)
, and this returns a long
integer.
(x,{flag = 0})
gives a basis for the kernel of the
matrix x
as columns of a matrix. A priori the matrix can have entries of
any type.
If x
is known to have integral entries, set flag = 1
.
Note: The library function ker_mod_p(x, p)
, where x
has
integer entries and p
is prime, which is equivalent to but many orders of
magnitude faster than matker(x*Mod(1,p))
and needs much less stack
space. To use it under GP, type install(ker_mod_p, GG)
first.
The library syntax is matker0(x,flag)
. Also available are ker(x)
(flag = 0
),
keri(x)
(flag = 1
) and ker_mod_p(x,p)
.
(x,{flag = 0})
gives an LLLreduced Zbasis
for the lattice equal to the kernel of the matrix x
as columns of the
matrix x
with integer entries (rational entries are not permitted).
If flag = 0
, uses a modified integer LLL algorithm.
If flag = 1
, uses matrixqz(x,2)
. If LLL reduction of the final result
is not desired, you can save time using matrixqz(matker(x),2)
instead.
If flag = 2
, uses another modified LLL. In the present version 2.2.0, only
independent rows are allowed in this case.
The library syntax is matkerint0(x,flag)
. Also available is
kerint(x)
(flag = 0
).
(x,d)
product of the matrix x
by the diagonal
matrix whose diagonal entries are those of the vector d
. Equivalent to,
but much faster than x*matdiagonal(d)
.
The library syntax is matmuldiagonal(x,d)
.
(x,y)
product of the matrices x
and y
knowing that the result is a diagonal matrix. Much faster than x*y
in
that case.
The library syntax is matmultodiagonal(x,y)
.
(x,{q})
creates as a matrix the lower triangular
Pascal triangle of order x+1
(i.e. with binomial coefficients
up to x
). If q
is given, compute the q
Pascal triangle (i.e. using
q
binomial coefficients).
The library syntax is matqpascal(x,q)
, where x
is a long
and q = NULL
is used
to omit q
. Also available is matpascal{x}.
(x)
rank of the matrix x
.
The library syntax is rank(x)
, and the result is a long
.
(m,n,{X},{Y},{expr = 0})
creation of the
m x n
matrix whose coefficients are given by the expression
expr. There are two formal parameters in expr, the first one
(X
) corresponding to the rows, the second (Y
) to the columns, and X
goes from 1 to m
, Y
goes from 1 to n
. If one of the last 3 parameters
is omitted, fill the matrix with zeroes.
The library syntax is matrice(GEN nlig,GEN ncol,entree *e1,entree *e2,char *expr)
.
(x,p)
x
being an m x n
matrix with m >= n
with rational or integer entries, this function has varying behaviour
depending on the sign of p
:
If p >= 0
, x
is assumed to be of maximal rank. This function returns a
matrix having only integral entries, having the same image as x
, such that
the GCD of all its n x n
subdeterminants is equal to 1 when p
is
equal to 0, or not divisible by p
otherwise. Here p
must be a prime
number (when it is nonzero). However, if the function is used when p
has
no small prime factors, it will either work or give the message ``impossible
inverse modulo'' and a nontrivial divisor of p
.
If p = 1
, this function returns a matrix whose columns form a basis of the
lattice equal to Z^n
intersected with the lattice generated by the
columns of x
.
If p = 2
, returns a matrix whose columns form a basis of the lattice equal
to Z^n
intersected with the Qvector space generated by the
columns of x
.
The library syntax is matrixqz0(x,p)
.
(x)
x
being a vector or matrix, returns a row vector
with two components, the first being the number of rows (1 for a row vector),
the second the number of columns (1 for a column vector).
The library syntax is matsize(x)
.
(X,{flag = 0})
if X
is a (singular or nonsingular)
square matrix outputs the vector of elementary divisors of X
(i.e. the
diagonal of the Smith normal form of X
).
The binary digits of flag mean:
1 (complete output): if set, outputs [U,V,D]
, where U
and V
are two
unimodular matrices such that UXV
is the diagonal matrix D
. Otherwise
output only the diagonal of D
.
2 (generic input): if set, allows polynomial entries. Otherwise, assume
that X
has integer coefficients.
4 (cleanup): if set, cleans up the output. This means that elementary
divisors equal to 1
will be deleted, i.e. outputs a shortened vector D'
instead of D
. If complete output was required, returns [U',V',D']
so
that U'XV' = D'
holds. If this flag is set, X
is allowed to be of the
form D
or [U,V,D]
as would normally be output with the cleanup flag
unset.
The library syntax is matsnf0(X,flag)
. Also available is smith(X)
(flag = 0
).
(x,y)
x
being an invertible matrix and y
a column
vector, finds the solution u
of x*u = y
, using Gaussian elimination. This
has the same effect as, but is a bit faster, than x^{1}*y
.
The library syntax is gauss(x,y)
.
(m,d,y,{flag = 0})
m
being any integral matrix,
d
a vector of positive integer moduli, and y
an integral
column vector, gives a small integer solution to the system of congruences
sum_i m_{i,j}x_j = y_i (mod d_i)
if one exists, otherwise returns
zero. Shorthand notation: y
(resp. d
) can be given as a single integer,
in which case all the y_i
(resp. d_i
) above are taken to be equal to y
(resp. d
).
If flag = 1
, all solutions are returned in the form of a twocomponent row
vector [x,u]
, where x
is a small integer solution to the system of
congruences and u
is a matrix whose columns give a basis of the homogeneous
system (so that all solutions can be obtained by adding x
to any linear
combination of columns of u
). If no solution exists, returns zero.
The library syntax is matsolvemod0(m,d,y,flag)
. Also available
are gaussmodulo(m,d,y)
(flag = 0
)
and gaussmodulo2(m,d,y)
(flag = 1
).
(x)
assuming that the columns of the matrix x
are linearly independent (if they are not, an error message is issued), finds
a square invertible matrix whose first columns are the columns of x
,
i.e. supplement the columns of x
to a basis of the whole space.
The library syntax is suppl(x)
.
(x)
or x~
transpose of x
.
This has an effect only on vectors and matrices.
The library syntax is gtrans(x)
.
(q)
decomposition into squares of the
quadratic form represented by the symmetric matrix q
. The result is a
matrix whose diagonal entries are the coefficients of the squares, and the
nondiagonal entries represent the bilinear forms. More precisely, if
(a_{ij})
denotes the output, one has
q(x) = sum_i a_{ii} (x_i + sum_{j > i} a_{ij} x_j)^2
The library syntax is sqred(x)
.
(x)
x
being a real symmetric matrix, this gives a
vector having two components: the first one is the vector of eigenvalues of
x
, the second is the corresponding orthogonal matrix of eigenvectors of
x
. The method used is Jacobi's method for symmetric matrices.
The library syntax is jacobi(x)
.
(x,{flag = 0})
LLL algorithm applied to the
columns of the (not necessarily square) matrix x
. The columns of x
must however be linearly independent, unless specified otherwise below. The
result is a transformation matrix T
such that x.T
is an LLLreduced
basis of the lattice generated by the column vectors of x
.
If flag = 0
(default), the computations are done with real numbers (i.e. not
with rational numbers) hence are fast but as presently programmed (version
2.2.0) are numerically unstable.
If flag = 1
, it is assumed that the corresponding Gram matrix is integral.
The computation is done entirely with integers and the algorithm is both
accurate and quite fast. In this case, x
needs not be of maximal rank, but
if it is not, T
will not be square.
If flag = 2
, similar to case 1, except x
should be an integer matrix whose
columns are linearly independent. The lattice generated by the columns of
x
is first partially reduced before applying the LLL algorithm. [A basis
is said to be partially reduced if v_i + v_j >= v_i
for any
two distinct basis vectors v_i, v_j
.]
This can be significantly faster than flag = 1
when one row is huge compared
to the other rows.
If flag = 3
, all computations are done in rational numbers. This does not
incur numerical instability, but is extremely slow. This function is
essentially superseded by case 1, so will soon disappear.
If flag = 4
, x
is assumed to have integral entries, but needs not be of
maximal rank. The result is a twocomponent vector of matrices : the
columns of the first matrix represent a basis of the integer kernel of x
(not necessarily LLLreduced) and the second matrix is the transformation
matrix T
such that x.T
is an LLLreduced Zbasis of the image
of the matrix x
.
If flag = 5
, case as case 4
, but x
may have polynomial coefficients.
If flag = 7
, uses an older version of case 0
above.
If flag = 8
, same as case 0
, where x
may have polynomial coefficients.
If flag = 9
, variation on case 1
, using content.
The library syntax is qflll0(x,flag,prec)
. Also available are
lll(x,prec)
(flag = 0
), lllint(x)
(flag = 1
), and
lllkerim(x)
(flag = 4
).
(x,{flag = 0})
same as qflll
except that the
matrix x
which must now be a square symmetric real matrix is the Gram
matrix of the lattice vectors, and not the coordinates of the vectors
themselves. The result is again the transformation matrix T
which gives (as
columns) the coefficients with respect to the initial basis vectors. The
flags have more or less the same meaning, but some are missing. In brief:
flag = 0
: numerically unstable in the present version 2.2.0.
flag = 1
: x
has integer entries, the computations are all done in integers.
flag = 4
: x
has integer entries, gives the kernel and reduced image.
flag = 5
: same as 4
for generic x
.
flag = 7
: an older version of case 0
.
The library syntax is qflllgram0(x,flag,prec)
. Also available are
lllgram(x,prec)
(flag = 0
), lllgramint(x)
(flag = 1
), and
lllgramkerim(x)
(flag = 4
).
(x,b,m,{flag = 0})
x
being a square and symmetric
matrix representing a positive definite quadratic form, this function
deals with the minimal vectors of x
, depending on flag
.
If flag = 0
(default), seeks vectors of square norm less than or equal to b
(for the norm defined by x
), and at most 2m
of these vectors. The result
is a threecomponent vector, the first component being the number of vectors,
the second being the maximum norm found, and the last vector is a matrix
whose columns are the vectors found, only one being given for each
pair + v
(at most m
such pairs).
If flag = 1
, ignores m
and returns the first vector whose norm is less than
b
.
In both these cases, x
is assumed to have integral entries, and the
function searches for the minimal nonzero vectors whenever b = 0
.
If flag = 2
, x
can have non integral real entries, but b = 0
is now
meaningless (uses FinckePohst algorithm).
The library syntax is qfminim0(x,b,m,flag,prec)
, also available are minim(x,b,m)
(flag = 0
), minim2(x,b,m)
(flag = 1
), and finally
fincke_pohst(x,b,m,prec)
(flag = 2
).
(x)
x
being a square and symmetric matrix with
integer entries representing a positive definite quadratic form, outputs the
perfection rank of the form. That is, gives the rank of the family of the s
symmetric matrices v_iv_i^t
, where s
is half the number of minimal
vectors and the v_i
(1 <= i <= s
) are the minimal vectors.
As a side note to oldtimers, this used to fail bluntly when x
had more
than 5000
minimal vectors. Beware that the computations can now be very
lengthy when x
has many minimal vectors.
The library syntax is perf(x)
.
(x)
signature of the quadratic form represented by the
symmetric matrix x
. The result is a twocomponent vector.
The library syntax is signat(x)
.
(x,y)
intersection of the two sets x
and y
.
The library syntax is setintersect(x,y)
.
(x)
returns true (1) if x
is a set, false (0) if
not. In PARI, a set is simply a row vector whose entries are strictly
increasing. To convert any vector (and other objects) into a set, use the
function Set
.
The library syntax is setisset(x)
, and this returns a long
.
(x,y)
difference of the two sets x
and y
,
i.e. set of elements of x
which do not belong to y
.
The library syntax is setminus(x,y)
.
(x,y,{flag = 0})
searches if y
belongs to the set
x
. If it does and flag
is zero or omitted, returns the index j
such that
x[j] = y
, otherwise returns 0. If flag
is nonzero returns the index j
where y
should be inserted, and 0
if it already belongs to x
(this is
meant to be used in conjunction with listinsert
).
This function works also if x
is a sorted list (see listsort
).
The library syntax is setsearch(x,y,flag)
which returns a long
integer.
(x,y)
union of the two sets x
and y
.
The library syntax is setunion(x,y)
.
(x)
this applies to quite general x
. If x
is not a
matrix, it is equal to the sum of x
and its conjugate, except for polmods
where it is the trace as an algebraic number.
For x
a square matrix, it is the ordinary trace. If x
is a
nonsquare matrix (but not a vector), an error occurs.
The library syntax is gtrace(x)
.
(x,y,{z})
extraction of components of the
vector or matrix x
according to y
. In case x
is a matrix, its
components are as usual the columns of x
. The parameter y
is a
component specifier, which is either an integer, a string describing a
range, or a vector.
If y
is an integer, it is considered as a mask: the binary bits of y
are
read from right to left, but correspond to taking the components from left to
right. For example, if y = 13 = (1101)_2
then the components 1,3 and 4 are
extracted.
If y
is a vector, which must have integer entries, these entries correspond
to the component numbers to be extracted, in the order specified.
If y
is a string, it can be
*
a single (nonzero) index giving a component number (a negative
index means we start counting from the end).
*
a range of the form "a..b"
, where a
and b
are
indexes as above. Any of a
and b
can be omitted; in this case, we take
as default values a = 1
and b = 1
, i.e. the first and last components
respectively. We then extract all components in the interval [a,b]
, in
reverse order if b < a
.
In addition, if the first character in the string is ^
, the
complement of the given set of indices is taken.
If z
is not omitted, x
must be a matrix. y
is then the line
specifier, and z
the column specifier, where the component specifier
is as explained above.
? v = [a, b, c, d, e]; ? vecextract(v, 5) \\ mask %1 = [a, c] ? vecextract(v, [4, 2, 1]) \\ component list %2 = [d, b, a] ? vecextract(v, "2..4") \\ interval %3 = [b, c, d] ? vecextract(v, "1..3") \\ interval + reverse order %4 = [e, d, c] ? vecextract([1,2,3], "^2") \\ complement %5 = [1, 3] ? vecextract(matid(3), "2..", "..") %6 = [0 1 0]
[0 0 1]
The library syntax is extract(x,y)
or matextract(x,y,z)
.
(x,{k},{flag = 0})
sorts the vector x
in ascending
order, using the heapsort method. x
must be a vector, and its components
integers, reals, or fractions.
If k
is present and is an integer, sorts according to the value of the
k
th subcomponents of the components of x
. k
can also be a vector,
in which case the
sorting is done lexicographically according to the components listed in the
vector k
. For example, if k = [2,1,3]
, sorting will be done with respect
to the second component, and when these are equal, with respect to the
first, and when these are equal, with respect to the third.
The binary digits of flag mean:
*
1: indirect sorting of the vector x
, i.e. if x
is an
n
component vector, returns a permutation of [1,2,...,n]
which
applied to the components of x
sorts x
in increasing order.
For example, vecextract(x, vecsort(x,,1))
is equivalent to
vecsort(x)
.
*
2: sorts x
by ascending lexicographic order (as per the
lex
comparison function).
*
4: use decreasing instead of ascending order.
The library syntax is vecsort0(x,k,flag)
. To omit k
, use NULL
instead. You can also
use the simpler functions
sort(x)
( = vecsort0(x,NULL,0)
).
indexsort(x)
( = vecsort0(x,NULL,1)
).
lexsort(x)
( = vecsort0(x,NULL,2)
).
Also available are sindexsort and sindexlexsort which return a
vector of Clong integers (private type t_VECSMALL
) v
, where
v[1]...v[n]
contain the indices. Note that the resulting v
is
not a generic PARI object, but is in general easier to use in C
programs!
(n,{X},{expr = 0})
creates a row vector (type
t_VEC
) with n
components whose components are the expression
expr evaluated at the integer points between 1 and n
. If one of the
last two arguments is omitted, fill the vector with zeroes.
The library syntax is vecteur(GEN nmax, entree *ep, char *expr)
.
(n,X,expr)
as vector, but returns a
column vector (type t_COL
).
The library syntax is vvecteur(GEN nmax, entree *ep, char *expr)
.
Although the GP calculator is programmable, it is useful to have preprogrammed a number of loops, including sums, products, and a certain number of recursions. Also, a number of functions from numerical analysis like numerical integration and summation of series will be described here.
One of the parameters in these loops must be the control variable, hence a
simple variable name. The last parameter can be any legal PARI expression,
including of course expressions using loops. Since it is much easier to
program directly the loops in library mode, these functions are mainly
useful for GP programming. The use of these functions in library mode is a
little tricky and its explanation will be mostly omitted, although the
reader can try and figure it out by himself by checking the example given
for the sum
function. In this section we only give the library
syntax, with no semantic explanation.
The letter X
will always denote any simple variable name, and represents
the formal parameter used in the function.
(numerical) integration: A number
of Romberglike integration methods are implemented (see intnum
as
opposed to intformal
which we already described). The user should not
require too much accuracy: 18 or 28 decimal digits is OK, but not much more.
In addition, analytical cleanup of the integral must have been done: there
must be no singularities in the interval or at the boundaries. In practice
this can be accomplished with a simple change of variable. Furthermore, for
improper integrals, where one or both of the limits of integration are plus
or minus infinity, the function must decrease sufficiently rapidly at
infinity. This can often be accomplished through integration by parts.
Finally, the function to be integrated should not be very small
(compared to the current precision) on the entire interval. This can
of course be accomplished by just multiplying by an appropriate
constant.
Note that infinity can be represented with essentially no loss of
accuracy by 1e4000. However beware of real underflow when dealing with
rapidly decreasing functions. For example, if one wants to compute the
int_0^ oo e^{x^2}dx
to 28 decimal digits, then one should set
infinity equal to 10 for example, and certainly not to 1e4000.
The integrand may have values belonging to a vector space over the real numbers; in particular, it can be complexvalued or vectorvalued.
See also the discrete summation methods below (sharing the prefix sum
).
(X = a,b,expr,{flag = 0})
numerical integration of
expr (smooth in ]a,b[
), with respect to X
.
Set flag = 0
(or omit it altogether) when a
and b
are not too large, the
function is smooth, and can be evaluated exactly everywhere on the interval
[a,b]
.
If flag = 1
, uses a general driver routine for doing numerical integration,
making no particular assumption (slow).
flag = 2
is tailored for being used when a
or b
are infinite. One
must have ab > 0
, and in fact if for example b = + oo
, then it is
preferable to have a
as large as possible, at least a >= 1
.
If flag = 3
, the function is allowed to be undefined (but continuous) at a
or b
, for example the function sin (x)/x
at x = 0
.
The library syntax is intnum0(entree*e,GEN a,GEN b,char*expr,long flag,long prec)
.
(X = a,b,expr,{x = 1})
product of expression expr,
initialized at x
, the formal parameter X
going from a
to b
. As for
sum
, the main purpose of the initialization parameter x
is to force
the type of the operations being performed. For example if it is set equal to
the integer 1, operations will start being done exactly. If it is set equal
to the real 1.
, they will be done using real numbers having the default
precision. If it is set equal to the power series 1+O(X^k)
for a certain
k
, they will be done using power series of precision at most k
. These
are the three most common initializations.
As an extreme example, compare
? prod(i=1, 100, 1  X^i); \\ this has degree 5050 !! time = 3,335 ms. ? prod(i=1, 100, 1  X^i, 1 + O(X^101)) time = 43 ms. %2 = 1  X  X^2 + X^5 + X^7  X^12  X^15 + X^22 + X^26  X^35  X^40 + \ X^51 + X^57  X^70  X^77 + X^92 + X^100 + O(X^101)
The library syntax is produit(entree *ep, GEN a, GEN b, char *expr, GEN x)
.
(X = a,b,expr)
product of expression expr,
initialized at 1. (i.e. to a real number equal to 1 to the current
realprecision
), the formal parameter X
ranging over the prime numbers
between a
and b
.
The library syntax is prodeuler(entree *ep, GEN a, GEN b, char *expr, long prec)
.
(X = a,expr,{flag = 0})
infinite product of
expression expr, the formal parameter X
starting at a
. The evaluation
stops when the relative error of the expression minus 1 is less than the
default precision. The expressions must always evaluate to an element of
C.
If flag = 1
, do the product of the (1+expr
) instead.
The library syntax is prodinf(entree *ep, GEN a, char *expr, long prec)
(flag = 0
), or
prodinf1 with the same arguments (flag = 1
).
(X = a,b,expr)
find a real root of expression
expr between a
and b
, under the condition
expr(X = a) * expr(X = b) <= 0
.
This routine uses Brent's method and can fail miserably if expr is
not defined in the whole of [a,b]
(try solve(x = 1, 2, tan(x)
).
The library syntax is zbrent(entree *ep, GEN a, GEN b, char *expr, long prec)
.
(X = a,b,expr,{x = 0})
sum of expression expr,
initialized at x
, the formal parameter going from a
to b
. As for
prod
, the initialization parameter x
may be given to force the type
of the operations being performed.
As an extreme example, compare
? sum(i=1, 5000, 1/i); \\ rational number: denominator has 2166 digits. time = 1,241 ms. ? sum(i=1, 5000, 1/i, 0.) time = 158 ms. %2 = 9.094508852984436967261245533
The library syntax is somme(entree *ep, GEN a, GEN b, char *expr, GEN x)
. This is to be
used as follows: ep
represents the dummy variable used in the
expression expr
/* compute a^2 + ... + b^2 */ { /* define the dummy variable "i" */ entree *ep = is_entry("i"); /* sum for a <= i <= b */ return somme(ep, a, b, "i^2", gzero); }
(X = a,expr,{flag = 0})
numerical summation of the
series expr, which should be an alternating series, the formal
variable X
starting at a
.
If flag = 0
, use an algorithm of F. Villegas as modified by D. Zagier. This
is much better than EulerVan Wijngaarden's method which was used
formerly.
Beware that the stopping criterion is that the term gets small enough, hence
terms which are equal to 0 will create problems and should be removed.
If flag = 1
, use a variant with slightly different polynomials. Sometimes
faster.
Divergent alternating series can sometimes be summed by this method, as well as series which are not exactly alternating (see for example Label se:user_defined).
Important hint: a significant speed gain can be obtained by
writing the (1)^X
which may occur in the expression as
(1.  X%2*2)
.
The library syntax is sumalt(entree *ep, GEN a, char *expr, long flag, long prec)
.
(n,X,expr)
sum of expression expr over
the positive divisors of n
.
Arithmetic functions like sigma use the multiplicativity of the
underlying expression to speed up the computation. In the present version
2.2.0, there is no way to indicate that expr is multiplicative in
n
, hence specialized functions should be prefered whenever possible.
The library syntax is divsum(entree *ep, GEN num, char *expr)
.
(X = a,expr)
infinite sum of expression
expr, the formal parameter X
starting at a
. The evaluation stops
when the relative error of the expression is less than the default precision.
The expressions must always evaluate to a complex number.
The library syntax is suminf(entree *ep, GEN a, char *expr, long prec)
.
(X = a,expr,{flag = 0})
numerical summation of the
series expr, which must be a series of terms having the same sign,
the formal
variable X
starting at a
. The algorithm used is Van Wijngaarden's trick
for converting such a series into an alternating one, and is quite slow.
Beware that the stopping criterion is that the term gets small enough, hence
terms which are equal to 0 will create problems and should be removed.
If flag = 1
, use slightly different polynomials. Sometimes faster.
The library syntax is sumpos(entree *ep, GEN a, char *expr, long flag, long prec)
.
Although plotting is not even a side purpose of PARI, a number of plotting functions are provided. Moreover, a lot of people felt like suggesting ideas or submitting huge patches for this section of the code. Among these, special thanks go to KlausPeter Nischke who suggested the recursive plotting and the forking/resizing stuff under X11, and Ilya Zakharevich who undertook a complete rewrite of the graphic code, so that most of it is now platformindependent and should be relatively easy to port or expand.
These graphic functions are either
*
highlevel plotting functions (all the functions starting with
ploth
) in which the user has little to do but explain what type of plot
he wants, and whose syntax is similar to the one used in the preceding
section (with somewhat more complicated flags).
*
lowlevel plotting functions, where every drawing primitive (point,
line, box, etc.) must be specified by the user. These lowlevel functions
(called rectplot functions, sharing the prefix plot
) work as
follows. You have at your disposal 16 virtual windows which are filled
independently, and can then be physically ORed on a single window at
userdefined positions. These windows are numbered from 0 to 15, and must be
initialized before being used by the function plotinit
, which specifies
the height and width of the virtual window (called a rectwindow in the
sequel). At all times, a virtual cursor (initialized at [0,0]
) is
associated to the window, and its current value can be obtained using the
function plotcursor
.
A number of primitive graphic objects (called rect objects) can then
be drawn in these windows, using a default color associated to that window
(which can be changed under X11, using the plotcolor
function, black
otherwise) and only the part of the object which is inside the window will be
drawn, with the exception of polygons and strings which are drawn entirely
(but the virtual cursor can move outside of the window). The ones sharing the
prefix plotr
draw relatively to the current position of the virtual
cursor, the others use absolute coordinates. Those having the prefix
plotrecth
put in the rectwindow a large batch of rect objects
corresponding to the output of the related ploth
function.
Finally, the actual physical drawing is done using the function
plotdraw
. Note that the windows are preserved so that further drawings
using the same windows at different positions or different windows can be
done without extra work. If you want to erase a window (and free the
corresponding memory), use the function plotkill
. It is not possible to
partially erase a window. Erase it completely, initialize it again and then
fill it with the graphic objects that you want to keep.
In addition to initializing the window, you may want to have a scaled
window to avoid unnecessary conversions. For this, use the function
plotscale
below. As long as this function is not called, the scaling is
simply the number of pixels, the origin being at the upper left and the
y
coordinates going downwards.
Note that in the present version 2.2.0 all these plotting functions (both low and high level) have been written for the X11window system (hence also for GUI's based on X11 such as Openwindows and Motif) only, though very little code remains which is actually platformdependent. A Suntools/Sunview, Macintosh, and an Atari/Gem port were provided for previous versions. These may be adapted in future releases.
Under X11/Suntools, the physical window (opened by plotdraw
or any
of the ploth*
functions) is completely separated from GP (technically,
a fork
is done, and the nongraphical memory is immediately freed in
the child process), which means you can go on working in the current GP
session, without having to kill the window first. Under X11, this window can
be closed, enlarged or reduced using the standard window manager functions.
No zooming procedure is implemented though (yet).
*
Finally, note that in the same way that printtex
allows you
to have a TeX output corresponding to printed results, the functions
starting with ps
allow you to have PostScript
output of the
plots. This will not be absolutely identical with the screen output, but will
be sufficiently close. Note that you can use PostScript output even if you do
not have the plotting routines enabled. The PostScript output is written in a
file whose name is derived from the psfile
default (./pari.ps
if
you did not tamper with it). Each time a new PostScript output is asked for,
the PostScript output is appended to that file. Hence the user must remove
this file, or change the value of psfile
, first if he does not want
unnecessary drawings from preceding sessions to appear. On the other hand, in
this manner as many plots as desired can be kept in a single file.
None of the graphic functions are available within the PARI library, you
must be under GP to use them. The reason for that is that you really should
not use PARI for heavyduty graphical work, there are much better specialized
alternatives around. This whole set of routines was only meant as a
convenient, but simpleminded, visual aid. If you really insist on using
these in your program (we warned you), the source (plot*.c
) should be
readable enough for you to achieve something.
(X = a,b,expr,{Ymin},{Ymax})
crude
(ASCII) plot of the function represented by expression expr from
a
to b
, with Y ranging from Ymin to Ymax. If
Ymin (resp. Ymax) is not given, the minima (resp. the
maxima) of the computed values of the expression is used instead.
(w,x2,y2)
let (x1,y1)
be the current position of the
virtual cursor. Draw in the rectwindow w
the outline of the rectangle which
is such that the points (x1,y1)
and (x2,y2)
are opposite corners. Only
the part of the rectangle which is in w
is drawn. The virtual cursor does
not move.
(w)
`clips' the content of rectwindow w
, i.e
remove all parts of the drawing that would not be visible on the screen.
Together with plotcopy
this function enables you to draw on a
scratchpad before commiting the part you're interested in to the final
picture.
(w,c)
set default color to c
in rectwindow w
.
In present version 2.2.0, this is only implemented for X11 window system,
and you only have the following palette to choose from:
1 = black, 2 = blue, 3 = sienna, 4 = red, 5 = cornsilk, 6 = grey, 7 = gainsborough.
Note that it should be fairly easy for you to hardwire some more colors by
tweaking the files rect.h
and plotX.c
. Userdefined
colormaps would be nice, and may be available in future versions.
(w1,w2,dx,dy)
copy the contents of rectwindow
w1
to rectwindow w2
, with offset (dx,dy)
.
(w)
give as a 2component vector the current
(scaled) position of the virtual cursor corresponding to the rectwindow w
.
(list)
physically draw the rectwindows given in list
which must be a vector whose number of components is divisible by 3. If
list = [w1,x1,y1,w2,x2,y2,...]
, the windows w1
, w2
, etc. are
physically placed with their upper left corner at physical position
(x1,y1)
, (x2,y2)
,...respectively, and are then drawn together.
Overlapping regions will thus be drawn twice, and the windows are considered
transparent. Then display the whole drawing in a special window on your
screen.
(s)
set the output file for plotting output. Special
filename 
redirects to the same place as PARI output.
(X = a,b,expr,{flag = 0},{n = 0})
high precision
plot of the function y = f(x)
represented by the expression expr, x
going from a
to b
. This opens a specific window (which is killed
whenever you click on it), and returns a fourcomponent vector giving the
coordinates of the bounding box in the form
[xmin,xmax,ymin,ymax]
.
Important note: Since this may involve a lot of function calls, it is advised to keep the current precision to a minimum (e.g. 9) before calling this function.
n
specifies the number of reference point on the graph (0 means use the
hardwired default values, that is: 1000 for general plot, 1500 for
parametric plot, and 15 for recursive plot).
If no flag
is given, expr is either a scalar expression f(X)
, in which
case the plane curve y = f(X)
will be drawn, or a vector
[f_1(X),...,f_k(X)]
, and then all the curves y = f_i(X)
will be drawn in
the same window.
The binary digits of flag
mean:
*
1: parametric plot. Here expr must be a vector with
an even number of components. Successive pairs are then understood as the
parametric coordinates of a plane curve. Each of these are then drawn.
For instance:
ploth(X = 0,2*Pi,[sin(X),cos(X)],1)
will draw a circle.
ploth(X = 0,2*Pi,[sin(X),cos(X)])
will draw two entwined sinusoidal
curves.
ploth(X = 0,2*Pi,[X,X,sin(X),cos(X)],1)
will draw a circle and the line
y = x
.
*
2: recursive plot. If this flag is set, only one
curve can be drawn at time, i.e. expr must be either a twocomponent
vector (for a single parametric curve, and the parametric flag has to
be set), or a scalar function. The idea is to choose pairs of successive
reference points, and if their middle point is not too far away from the
segment joining them, draw this as a local approximation to the curve.
Otherwise, add the middle point to the reference points. This is very fast,
and usually more precise than usual plot. Compare the results of
ploth(X = 1,1,sin(1/X),2) and ploth(X = 1,1,sin(1/X))
for instance. But beware that if you are extremely unlucky, or choose too few reference points, you may draw some nice polygon bearing little resemblance to the original curve. For instance you should never plot recursively an odd function in a symmetric interval around 0. Try
ploth(x = 20, 20, sin(x), 2)
to see why. Hence, it's usually a good idea to try and plot the same curve with slightly different parameters.
The other values toggle various display options:
*
4: do not rescale plot according to the computed extrema. This is
meant to be used when graphing multiple functions on a rectwindow (as a
plotrecth
call), in conjuction with plotscale
.
*
8: do not print the x
axis.
*
16: do not print the y
axis.
*
32: do not print frame.
*
64: only plot reference points, do not join them.
*
256: use splines to interpolate the points.
*
512: plot no x
ticks.
*
1024: plot no y
ticks.
*
2048: plot all ticks with the same length.
(listx,listy,{flag = 0})
given
listx and listy two vectors of equal length, plots (in high
precision) the points whose (x,y)
coordinates are given in listx
and listy. Automatic positioning and scaling is done, but with the
same scaling factor on x
and y
. If flag
is 1, join points, other non0
flags toggle display options and should be combinations of bits 2^k
, k
E<gt>= 3
as in ploth
.
()
return data corresponding to the output window
in the form of a 6component vector: window width and height, sizes for ticks
in horizontal and vertical directions (this is intended for the gnuplot
interface and is currently not significant), width and height of characters.
(w,x,y)
initialize the rectwindow w
to width x
and
height y
, and position the virtual cursor at (0,0)
. This destroys any rect
objects you may have already drawn in w
.
The plotting device imposes an upper bound for x
and y
, for instance the
number of pixels for screen output. These bounds are available through the
plothsizes
function. The following sequence initializes in a portable way
(i.e independant of the output device) a window of maximal size, accessed through
coordinates in the [0,1000] x [0,1000]
range :
s = plothsizes(); plotinit(0, s[1]1, s[2]1); plotscale(0, 0,1000, 0,1000);
(w)
erase rectwindow w
and free the corresponding
memory. Note that if you want to use the rectwindow w
again, you have to
use initrect
first to specify the new size. So it's better in this case
to use initrect
directly as this throws away any previous work in the
given rectwindow.
(w,X,Y,{flag = 0})
draw on the rectwindow w
the polygon such that the (x,y)coordinates of the vertices are in the
vectors of equal length X
and Y
. For simplicity, the whole
polygon is drawn, not only the part of the polygon which is inside the
rectwindow. If flag
is nonzero, close the polygon. In any case, the
virtual cursor does not move.
X
and Y
are allowed to be scalars (in this case, both have to).
There, a single segment will be drawn, between the virtual cursor current
position and the point (X,Y)
. And only the part thereof which
actually lies within the boundary of w
. Then move the virtual cursor
to (X,Y)
, even if it is outside the window. If you want to draw a
line from (x1,y1)
to (x2,y2)
where (x1,y1)
is not necessarily the
position of the virtual cursor, use plotmove(w,x1,y1)
before using this
function.
(w,type)
change the type of lines
subsequently plotted in rectwindow w
. type 2
corresponds to
frames, 1
to axes, larger values may correspond to something else. w =
1
changes highlevel plotting. This is only taken into account by the
gnuplot
interface.
(w,x,y)
move the virtual cursor of the rectwindow w
to position (x,y)
.
(w,X,Y)
draw on the rectwindow w
the
points whose (x,y)
coordinates are in the vectors of equal length X
and
Y
and which are inside w
. The virtual cursor does not move. This
is basically the same function as plothraw
, but either with no scaling
factor or with a scale chosen using the function plotscale
.
As was the case with the plotlines
function, X
and Y
are allowed to
be (simultaneously) scalar. In this case, draw the single point (X,Y)
on
the rectwindow w
(if it is actually inside w
), and in any case
move the virtual cursor to position (x,y)
.
(w,size)
changes the ``size'' of following
points in rectwindow w
. If w = 1
, change it in all rectwindows.
This only works in the gnuplot
interface.
(w,type)
change the type of
points subsequently plotted in rectwindow w
. type = 1
corresponds to a dot, larger values may correspond to something else. w = 1
changes highlevel plotting. This is only taken into account by the
gnuplot
interface.
(w,dx,dy)
draw in the rectwindow w
the outline of
the rectangle which is such that the points (x1,y1)
and (x1+dx,y1+dy)
are
opposite corners, where (x1,y1)
is the current position of the cursor.
Only the part of the rectangle which is in w
is drawn. The virtual cursor
does not move.
(w,X = a,b,expr,{flag = 0},{n = 0})
writes to
rectwindow w
the curve output of ploth
(w,X = a,b,expr,flag,n)
.
(w,data,{flag = 0})
plot graph(s)
for
data in rectwindow w
. flag
has the same significance here as in
ploth
, though recursive plot is no more significant.
data is a vector of vectors, each corresponding to a list a coordinates.
If parametric plot is set, there must be an even number of vectors, each
successive pair corresponding to a curve. Otherwise, the first one containe
the x
coordinates, and the other ones contain the y
coordinates
of curves to plot.
(w,dx,dy)
draw in the rectwindow w
the part of the
segment (x1,y1)(x1+dx,y1+dy)
which is inside w
, where (x1,y1)
is the
current position of the virtual cursor, and move the virtual cursor to
(x1+dx,y1+dy)
(even if it is outside the window).
(w,dx,dy)
move the virtual cursor of the rectwindow
w
to position (x1+dx,y1+dy)
, where (x1,y1)
is the initial position of
the cursor (i.e. to position (dx,dy)
relative to the initial cursor).
(w,dx,dy)
draw the point (x1+dx,y1+dy)
on the
rectwindow w
(if it is inside w
), where (x1,y1)
is the current position
of the cursor, and in any case move the virtual cursor to position
(x1+dx,y1+dy)
.
(w,x1,x2,y1,y2)
scale the local coordinates of the
rectwindow w
so that x
goes from x1
to x2
and y
goes from y1
to
y2
(x2 < x1
and y2 < y1
being allowed). Initially, after the initialization
of the rectwindow w
using the function plotinit
, the default scaling
is the graphic pixel count, and in particular the y
axis is oriented
downwards since the origin is at the upper left. The function plotscale
allows to change all these defaults and should be used whenever functions are
graphed.
(w,x,{flag = 0})
draw on the rectwindow w
the
String x
(see Label se:strings), at the current position of the cursor.
flag is used for justification: bits 1 and 2 regulate horizontal alignment: left if 0, right if 2, center if 1. Bits 4 and 8 regulate vertical alignment: bottom if 0, top if 8, vcenter if 4. Can insert additional small gap between point and string: horizontal if bit 16 is set, vertical if bit 32 is set (see the tutorial for an example).
(term)
sets terminal where high resolution
plots go (this is currently only taken into account by the gnuplot
graphical driver). Using the gnuplot
driver, possible terminals are
the same as in gnuplot. If term is ``?'', lists possible values.
Terminal options can be appended to the terminal name and space; terminal
size can be put immediately after the name, as in "gif = 300,200"
.
Positive return value means success.
(list)
same as plotdraw
, except that the
output is a PostScript program appended to the psfile
.
(X = a,b,expr)
same as ploth
, except that the
output is a PostScript program appended to the psfile
.
(listx,listy)
same as plothraw
,
except that the output is a PostScript program appended to the psfile
.
=head2 Control statements.
A number of control statements are available under GP. They are simpler and
have a syntax slightly different from their C counterparts, but are quite
powerful enough to write any kind of program. Some of them are specific to
GP, since they are made for number theorists. As usual, X
will denote any
simple variable name, and seq will always denote a sequence of
expressions, including the empty sequence.
({n = 1})
interrupts execution of current seq, and
immediately exits from the n
innermost enclosing loops, within the
current function call (or the top level loop). n
must be bigger than 1.
If n
is greater than the number of enclosing loops, all enclosing loops
are exited.
(X = a,b,seq)
the formal variable X
going from
a
to b
, the seq is evaluated. Nothing is done if a > b
.
a
and b
must be in R.
(n,X,seq)
the formal variable X
ranging
through the positive divisors of n
, the sequence seq is evaluated.
n
must be of type integer.
(X = a,b,seq)
the formal variable X
ranging over the prime numbers between a
to b
(including a
and b
if they are prime), the seq is evaluated. More precisely, the value
of X
is incremented to the smallest prime strictly larger than X
at the
end of each iteration. Nothing is done if a > b
. Note that a
and b
must
be in R.
? { forprime(p = 2, 12, print(p); if (p == 3, p = 6); ) } 2 3 7 11
(X = a,b,s,seq)
the formal variable X
going from a
to b
, in increments of s
, the seq is evaluated.
Nothing is done if s > 0
and a > b
or if s < 0
and a < b
. s
must be in
R^*
or a vector of steps [s_1,...,s_n]
. In the latter case, the
successive steps are used in the order they appear in s
.
? forstep(x=5, 20, [2,4], print(x)) 5 7 11 13 17 19
(H = G,{B},seq)
executes seq for
each subgroup H
of the abelian group G
(given in
SNF form or as a vector of elementary divisors),
whose index is bounded by bound. The subgroups are not ordered in any
obvious way, unless G
is a p
group in which case Birkhoff's algorithm
produces them by decreasing index. A subgroup is given as a matrix
whose columns give its generators on the implicit generators of G
. For
example, the following prints all subgroups of index less than 2 in G =
B<I<Z>>/2B<I<Z>> g_1 x B<I<Z>>/2B<I<Z>> g_2
:
? G = [2,2]; forsubgroup(H=G, 2, print(H)) [1; 1] [1; 2] [2; 1] [1, 0; 1, 1]
The last one, for instance is generated by (g_1, g_1 + g_2)
. This
routine is intended to treat huge groups, when subgrouplist is not an
option due to the sheer size of the output.
For maximal speed the subgroups have been left as produced by the algorithm.
To print them in canonical form (as left divisors of G
in
HNF form), one can for instance use
? G = matdiagonal([2,2]); forsubgroup(H=G, 2, print(mathnf(concat(G,H)))) [2, 1; 0, 1] [1, 0; 0, 2] [2, 0; 0, 1] [1, 0; 0, 1]
Note that in this last representation, the index [G:H]
is given by the
determinant.
(X = v,seq,{flag = 0})
v
being an n
component
vector (where n
is arbitrary) of twocomponent vectors [a_i,b_i]
for 1 <= i <= n
, the seq is evaluated with the formal variable
X[1]
going from a_1
to b_1
,...,X[n]
going from a_n
to b_n
.
The formal variable with the highest index moves the fastest. If flag = 1
,
generate only nondecreasing vectors X
, and if flag = 2
, generate only
strictly increasing vectors X
.
(a,{seq1},{seq2})
if a
is nonzero,
the expression sequence seq1 is evaluated, otherwise the expression
seq2 is evaluated. Of course, seq1 or seq2 may be empty,
so if (a,seq)
evaluates seq if a
is not equal to zero
(you don't have to write the second comma), and does nothing otherwise,
whereas if (a,,seq)
evaluates seq if a
is equal to
zero, and does nothing otherwise. You could get the same result using
the !
(not
) operator: if (!a,seq)
.
Note that the boolean operators &&
and 
are evaluated
according to operator precedence as explained in Label se:operators, but
that, contrary to other operators, the evaluation of the arguments is
stopped as soon as the final truth value has been determined. For instance
if (reallydoit && longcomplicatedfunction(), ...)%
is a perfectly safe statement.
Recall that functions such as break
and next
operate on
loops (such as forxxx
, while
, until
). The if
statement is not a loop (obviously!).
({n = 1})
interrupts execution of current seq
,
resume the next iteration of the innermost enclosing loop, within the
current fonction call (or top level loop). If n
is specified, resume at
the n
th enclosing loop. If n
is bigger than the number of enclosing
loops, all enclosing loops are exited.
({x = 0})
returns from current subroutine, with
result x
.
(a,seq)
evaluates expression sequence seq
until a
is not equal to 0 (i.e. until a
is true). If a
is initially
not equal to 0, seq is evaluated once (more generally, the condition
on a
is tested after execution of the seq, not before as in
while
).
(a,seq)
while a
is nonzero evaluate the
expression sequence seq. The test is made before evaluating
the seq
, hence in particular if a
is initially equal to zero the
seq will not be evaluated at all.
In addition to the general PARI functions, it is necessary to have some functions which will be of use specifically for GP, though a few of these can be accessed under library mode. Before we start describing these, we recall the difference between strings and keywords (see Label se:strings): the latter don't get expanded at all, and you can type them without any enclosing quotes. The former are dynamic objects, where everything outside quotes gets immediately expanded.
We need an additional notation for this chapter. An argument between braces,
followed by a star, like {str}*
, means that any number of such
arguments (possibly none) can be given.
(S,str)
changes the help
message for the symbol S
. The string str is expanded on the spot
and stored as the online help for S
. If S
is a function you have
defined, its definition will still be printed before the message str.
It is recommended that you document global variables and user functions in
this way. Of course GP won't protest if you don't do it.
There's nothing to prevent you from modifying the help of builtin PARI functions (but if you do, we'd like to hear why you needed to do it!).
(newkey,key)
defines the keyword
newkey as an alias for keyword key. key must correspond
to an existing function name. This is different from the general user
macros in that alias expansion takes place immediately upon execution,
without having to look up any function code, and is thus much faster. A
sample alias file misc/gpalias
is provided with the standard
distribution. Alias commands are meant to be read upon startup from the
.gprc
file, to cope with function names you are dissatisfied with, and
should be useless in interactive usage.
({x = 0})
this is a very special operation which
allows the user to change the stack size after initialization. x
must be a nonnegative integer. If x! = 0
, a new stack of size 16*\lceil
x/16\rceil
bytes will be allocated, all the PARI data on the old stack will
be moved to the new one, and the old stack will be discarded. If x = 0
, the
size of the new stack will be twice the size of the old one.
Although it is a function, this must be the last instruction in any GP
sequence. The technical reason is that this routine usually moves the stack,
so objects from the current sequence might not be correct anymore. Hence, to
prevent such problems, this routine terminates by a longjmp
(just as an
error would) and not by a return.
The library syntax is allocatemoremem(x)
, where x
is an unsigned long, and the return type
is void. GP uses a variant which ends by a longjmp
.
({key},{val},{flag})
sets the default
corresponding to keyword key to value val. val is a string
(which of course accepts numeric arguments without adverse effects, due to the
expansion mechanism). See Label se:defaults for a list of available
defaults, and Label se:meta for some shortcut alternatives. Typing
default()
(or \d
) yields the complete default list as well as
their current values.
If val is omitted, prints the current value of default key.
If flag
is set, returns the result instead of printing it.
({str}*)
outputs its argument list (each of them interpreted as a string), then interrupts the running GP program, returning to the input prompt.
Example: error("n = ", n, " is not squarefree !")
.
Note that, due to the automatic concatenation of strings, you could in fact use only one argument, just by suppressing the commas.
(str)
the string str is the name of an external command (i.e. one you would type from your UNIX shell prompt). This command is immediately run and its input fed into GP, just as if read from a file.
()
returns a twocomponent row vector giving the number of objects on the heap and the amount of memory they occupy in long words. Useful mainly for debugging purposes.
The library syntax is getheap()
.
()
returns the current value of the random number seed. Useful mainly for debugging purposes.
The library syntax is getrand()
, returns a C long.
()
returns the current value of
topavma
,
i.e. the number of bytes used up to now on the stack. Should be equal to 0
in between commands. Useful mainly for debugging purposes.
The library syntax is getstack()
, returns a C long.
()
returns the time (in milliseconds) elapsed since
either the last call to gettime
, or to the beginning of the containing
GP instruction (if inside GP), whichever came last.
The library syntax is gettime()
, returns a C long.
({list of variables})
declares the corresponding variables to be global. From now on, you will be forbidden to use them as formal parameters for function definitions or as loop indexes. This is especially useful when patching together various scripts, possibly written with different naming conventions. For instance the following situation is dangerous:
p = 3 \\ fix characteristic ... forprime(p = 2, N, ...) f(p) = ...
since within the loop or within the function's body (even worse: in the
subroutines called in that scope), the true global value of p
will be
hidden. If the statement global(p = 3)
appears at the beginning of
the script, then both expressions will trigger syntax errors.
Calling global
without arguments prints the list of global variables in
use. In particular, eval(global)
will output the values of all local
variables.
()
reads a string, interpreted as a GP expression,
from the input file, usually standard input (i.e. the keyboard). If a
sequence of expressions is given, the result is the result of the last
expression of the sequence. When using this instruction, it is useful to
prompt for the string by using the print1
function. Note that in the
present version 2.19 of pari.el
, when using GP under GNU Emacs (see
Label se:emacs) one must prompt for the string, with a string
which ends with the same prompt as any of the previous ones (a "? "
will do for instance).
(name,code,{gpname},{lib})
loads from dynamic library lib the function name. Assigns to it
the name gpname in this GP session, with argument code code (see
Label se:gp.interface for an explanation of those). If lib is
omitted, uses libpari.so
. If gpname is omitted, uses
name.
This function is useful for adding custom functions to the GP interpreter,
or picking useful functions from unrelated libraries. For instance, it
makes the function system
obsolete:
? install(system, vs, sys, "libc.so") ? sys("ls gp*") gp.c gp.h gp_rl.c
But it also gives you access to all (non static) functions defined in the
PARI library. For instance, the function GEN addii(GEN x, GEN y)
adds
two PARI integers, and is not directly accessible under GP (it's eventually
called by the +
operator of course):
? install("addii", "GG") ? addii(1, 2) %1 = 3
Caution: This function may not work on all systems, especially when GP has been compiled statically. In that case, the first use of an installed function will provoke a Segmentation Fault, i.e. a major internal blunder (this should never happen with a dynamically linked executable). Hence, if you intend to use this function, please check first on some harmless example such as the ones above that it works properly on your machine.
(s)
kills the present value of the
variable, alias or userdefined function s
. The corresponding identifier
can now be used to name any GP object (variable or function). This is the
only way to replace a variable by a function having the same name (or the
other way round), as in the following example:
? f = 1 %1 = 1 ? f(x) = 0 *** unused characters: f(x)=0 ^ ? kill(f) ? f(x) = 0 ? f() %2 = 0
When you kill a variable, all objects that used it become invalid. You
can still display them, even though the killed variable will be printed in a
funny way (following the same convention as used by the library function
fetch_var
, see Label se:vars). For example:
? a^2 + 1 %1 = a^2 + 1 ? kill(a) ? %1 %2 = #<1>^2 + 1
If you simply want to restore a variable to its ``undefined'' value
(monomial of degree one), use the quote operator: a = 'a
.
Predefined symbols (x
and GP function names) cannot be killed.
({str}*)
outputs its (string) arguments in raw format, ending with a newline.
({str}*)
outputs its (string) arguments in raw
format, without ending with a newline (note that you can still embed newlines
within your strings, using the \n
notation !).
({str}*)
outputs its (string) arguments in prettyprint (beautified) format, ending with a newline.
({str}*)
outputs its (string) arguments in prettyprint (beautified) format, without ending with a newline.
({str}*)
outputs its (string) arguments in
TeX format. This output can then be used in a TeX manuscript.
The printing is done on the standard output. If you want to print it to a
file you should use writetex
(see there).
Another possibility is to enable the log
default
(see Label se:defaults).
You could for instance do:
default(logfile, "new.tex"); default(log, 1); printtex(result);
(You can use the automatic string expansion/concatenation process to have dynamic file names if you wish).
()
exits GP.
({str})
reads in the file whose name results from the expansion of the string str. If str is omitted, rereads the last file that was fed into GP. The return value is the result of the last expression evaluated.
({x = []})
x
must be a vector. If x
is the
empty vector, this gives the vector whose components are the existing
variables in increasing order (i.e. in decreasing importance). Killed
variables (see kill
) will be shown as 0
. If x
is
nonempty, it must be a permutation of variable names, and this permutation
gives a new order of importance of the variables, for output only. For
example, if the existing order is [x,y,z]
, then after
reorder([z,x])
the order of importance of the variables, with respect
to output, will be [z,y,x]
. The internal representation is unaffected.
(n)
reseeds the random number generator to the value
n
. The initial seed is n = 1
.
The library syntax is setrand(n)
, where n
is a long
. Returns n
.
(str)
str is a string representing
a system command. This command is executed, its output written to the
standard output (this won't get into your logfile), and control returns
to the PARI system. This simply calls the C system
command.
({e}, {rec}, {seq})
tries to
execute seq, trapping error e
, that is effectively preventing it
from aborting computations in the usual way; the recovery sequence
rec is executed if the error occurs and the evaluation of rec
becomes the result of the command. If e
is omitted, all exceptions are
trapped. Note in particular that hitting ^C
(ControlC) raises an
exception.
? \\ trap division by 0 ? inv(x) = trap (gdiver2, INFINITY, 1/x) ? inv(2) %1 = 1/2 ? inv(0) %2 = INFINITY
If seq is omitted, defines rec as a default action when
encountering exception e
. The error message is printed, as well as the
result of the evaluation of rec, and the control is given back to the
GP prompt. In particular, current computation is then lost.
The following error handler prints the list of all user variables, then stores in a file their name and their values:
? { trap( , print(reorder); write("crash", reorder); write("crash", eval(reorder))) }
If no recovery code is given (rec is omitted) a socalled break loop will be started. During a break loop, all commands are read and evaluated as during the main GP loop (except that no history of results is kept).
To get out of the break loop, you can use next
, break
or
return
; reading in a file by \r
will also terminate the loop once
the file has been read (read
will remain in the break loop). If the
error is not fatal (^C
is the only nonfatal error), next
will continue the computation as if nothing had happened (except of course,
you may have changed GP state during the break loop); otherwise control
will come back to the GP prompt. After a user interrupt (^C
),
entering an empty input line (i.e hitting the return key) has the same
effect as next
.
Break loops are useful as a debugging tool to inspect the values of GP
variables to understand why a problem occurred, or to change GP behaviour
(increase debugging level, start storing results in a logfile, modify
parameters...) in the middle of a long computation (hit ^C
, type
in your modifications, then type next
).
If rec is the empty string ""
the last default handler is popped
out, and replaced by the previous one for that error.
Note: The interface is currently not adequate for trapping individual exceptions. In the current version 2.2.0, the following keywords are recognized, but the name list will be expanded and changed in the future (all library mode errors can be trapped: it's a matter of defining the keywords to GP, and there are currently far too many useless ones):
accurer
: accuracy problem
gdiver2
: division by 0
archer
: not available on this architecture or operating system
typeer
: wrong type
errpile
: the PARI stack overflows
(x,{t})
this is useful only under GP. If t
is
not present, returns the internal type number of the PARI object x
.
Otherwise, makes a copy of x
and sets its type equal to type t
, which
can be either a number or, preferably since internal codes may eventually
change, a symbolic name such as t_FRACN
(you can skip the t_
part here, so that FRACN
by itself would also be all right). Check out
existing type names with the metacommand \t
.
GP won't let you create meaningless objects in this way where the internal
structure doesn't match the type. This function can be useful to create
reducible rationals (type t_FRACN
) or rational functions (type
t_RFRACN
). In fact it's the only way to do so in GP. In this case, the
created object, as well as the objects created from it, will not be reduced
automatically, making some operations a bit faster.
There is no equivalent library syntax, since the internal functions typ
and settyp
are available. Note that settyp
does not
create a copy of x
, contrary to most PARI functions. It also doesn't
check for consistency. settyp
just changes the type in place and
returns nothing. typ
returns a C long integer. Note also the different
spellings of the internal functions (set
)typ
and of the GP
function type
, which is due to the fact that type
is a reserved
identifier for some C compilers.
(key)
if keyword key is the name
of a function that was present in GP version 1.39.15 or lower, outputs
the new function name and syntax, if it changed at all (387
out of 560
did).
(filename,{str*})
writes (appends)
to filename the remaining arguments, and appends a newline (same output
as print
).
(filename,{str*})
writes (appends) to
filename the remaining arguments without a trailing newline
(same output as print1
).
(filename,{str*})
as write
,
in TeX format.