(gmp.info.gz) Formatted Input Strings
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Formatted Input Strings
=======================
`gmp_scanf' and friends accept format strings similar to the standard C
`scanf' ( Formatted Input (libc)Formatted Input.). A format
specification is of the form
% [flags] [width] [type] conv
GMP adds types `Z', `Q' and `F' for `mpz_t', `mpq_t' and `mpf_t'
respectively. `Z' and `Q' behave like integers. `Q' will read a `/'
and a denominator, if present. `F' behaves like a float.
GMP variables don't require an `&' when passed to `gmp_scanf', since
they're already "call-by-reference". For example,
/* to read say "a(5) = 1234" */
int n;
mpz_t z;
gmp_scanf ("a(%d) = %Zd\n", &n, z);
mpq_t q1, q2;
gmp_sscanf ("0377 + 0x10/0x11", "%Qi + %Qi", q1, q2);
/* to read say "topleft (1.55,-2.66)" */
mpf_t x, y;
char buf[32];
gmp_scanf ("%31s (%Ff,%Ff)", buf, x, y);
All the standard C `scanf' types behave the same as in the C library
`scanf', and can be freely intermixed with the GMP extensions. In the
current implementation the standard parts of the format string are
simply handed to `scanf' and only the GMP extensions handled directly.
The flags accepted are as follows. `a' and `'' will depend on
support from the C library, and `'' cannot be used with GMP types.
* read but don't store
a allocate a buffer (string conversions)
' grouped digits, GLIBC style (not GMP
types)
The standard types accepted are as follows. `h' and `l' are
portable, the rest will depend on the compiler (or include files) for
the type and the C library for the input.
h short
hh char
j intmax_t or uintmax_t
l long int, double or wchar_t
ll long long
L long double
q quad_t or u_quad_t
t ptrdiff_t
z size_t
The GMP types are
F mpf_t, float conversions
Q mpq_t, integer conversions
Z mpz_t, integer conversions
The conversions accepted are as follows. `p' and `[' will depend on
support from the C library, the rest are standard.
c character or characters
d decimal integer
e E f g G float
i integer with base indicator
n characters read so far
o octal integer
p pointer
s string of non-whitespace characters
u decimal integer
x X hex integer
[ string of characters in a set
`e', `E', `f', `g' and `G' are identical, they all read either fixed
point or scientific format, and either upper or lower case `e' for the
exponent in scientific format.
C99 style hex float format (`printf %a', Formatted Output
Strings) is always accepted for `mpf_t', but for the standard float
types it will depend on the C library.
`x' and `X' are identical, both accept both upper and lower case
hexadecimal.
`o', `u', `x' and `X' all read positive or negative values. For the
standard C types these are described as "unsigned" conversions, but
that merely affects certain overflow handling, negatives are still
allowed (per `strtoul', Parsing of Integers (libc)Parsing of
Integers.). For GMP types there are no overflows, so `d' and `u' are
identical.
`Q' type reads the numerator and (optional) denominator as given.
If the value might not be in canonical form then `mpq_canonicalize'
must be called before using it in any calculations ( Rational
Number Functions).
`Qi' will read a base specification separately for the numerator and
denominator. For example `0x10/11' would be 16/11, whereas `0x10/0x11'
would be 16/17.
`n' can be used with any of the types above, even the GMP types.
`*' to suppress assignment is allowed, though in that case it would do
nothing at all.
Other conversions or types that might be accepted by the C library
`scanf' cannot be used through `gmp_scanf'.
Whitespace is read and discarded before a field, except for `c' and
`[' conversions.
For float conversions, the decimal point character (or string)
expected is taken from the current locale settings on systems which
provide `localeconv' ( Locales and Internationalization
(libc)Locales.). The C library will normally do the same for standard
float input.
The format string is only interpreted as plain `char's, multibyte
characters are not recognised. Perhaps this will change in the future.
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