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(gmp.info)Formatted Output Strings

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Format Strings
==============

   `gmp_printf' and friends accept format strings similar to the
standard C `printf' (Note: Formatted Output.).
A format specification is of the form

     % [flags] [width] [.[precision]] [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 print a `/'
and a denominator, if needed.  `F' behaves like a float.  For example,

     mpz_t z;
     gmp_printf ("%s is an mpz %Zd\n", "here", z);
     
     mpq_t q;
     gmp_printf ("a hex rational: %#40Qx\n", q);
     
     mpf_t f;
     int   n;
     gmp_printf ("fixed point mpf %.*Ff with %d digits\n", n, f, n);

   All the standard C `printf' types behave the same as the C library
`printf', and can be freely intermixed with the GMP extensions.  In the
current implementation the standard parts of the format string are
simply handed to `printf' and only the GMP extensions handled directly.

   The flags accepted are as follows.  GLIBC style ' (Note: Locales and
Internationalization.) is only for the standard C types
(not the GMP types), and only if the C library supports it.

     0         pad with zeros (rather than spaces)
     #         show the base with `0x', `0X' or `0'
     +         always show a sign
     (space)   show a space or a `-' sign
     '         group 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 output.

     h         short
     hh        char
     j         intmax_t or uintmax_t
     l         long or wchar_t
     ll        same as L
     L         long long or 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.  `a' and `A' are always
supported for `mpf_t' but depend on the C library for standard C float
types.  `m' and `p' depend on the C library.

     a A       hex floats, GLIBC style
     c         character
     d         decimal integer
     e E       scientific format float
     f         fixed point float
     i         same as d
     g G       fixed or scientific float
     m         `strerror' string, GLIBC style
     n         characters written so far
     o         octal integer
     p         pointer
     s         string
     u         unsigned integer
     x X       hex integer

   `o', `x' and `X' are unsigned for the standard C types, but for `Z'
and `Q' a sign is included.  `u' is not meaningful for `Z' and `Q'.

   `n' can be used with any of the types, even the GMP types.

   Other types or conversions that might be accepted by the C library
`printf' cannot be used through `gmp_printf', this includes for
instance extensions registered with GLIBC `register_printf_function'.
Also currently there's no support for POSIX `$' style numbered arguments
(perhaps this will be added in the future).

   The precision field has it's usual meaning for integer `Z' and float
`F' types, but is currently undefined for `Q' and should not be used
with that.

   `mpf_t' conversions only ever generate as many digits as can be
accurately represented by the operand, the same as `mpf_get_str' does.
Zeros will be used if necessary to pad to the requested precision.  This
happens even for an `f' conversion of an `mpf_t' which is an integer,
for instance 2^1024 in an `mpf_t' of 128 bits precision will only
produce about 20 digits, then pad with zeros to the decimal point.  An
empty precision field like `%.Fe' or `%.Ff' can be used to specifically
request all significant digits.

   The decimal point character (or string) is taken from the current
locale settings on systems which provide `localeconv' (Note: Locales
and Internationalization.).  The C library will normally
do the same for standard float output.