( 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
    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
    `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
    `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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