<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <!-- This manual describes how to install and use the GNU multiple precision arithmetic library, version 6.1.0. Copyright 1991, 1993-2015 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being "A GNU Manual", and with the Back-Cover Texts being "You have freedom to copy and modify this GNU Manual, like GNU software". 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A format specification is of the form </p> <div class="example"> <pre class="example">% [flags] [width] [.[precision]] [type] conv </pre></div> <p>GMP adds types ‘<samp>Z</samp>’, ‘<samp>Q</samp>’ and ‘<samp>F</samp>’ for <code>mpz_t</code>, <code>mpq_t</code> and <code>mpf_t</code> respectively, ‘<samp>M</samp>’ for <code>mp_limb_t</code>, and ‘<samp>N</samp>’ for an <code>mp_limb_t</code> array. ‘<samp>Z</samp>’, ‘<samp>Q</samp>’, ‘<samp>M</samp>’ and ‘<samp>N</samp>’ behave like integers. ‘<samp>Q</samp>’ will print a ‘<samp>/</samp>’ and a denominator, if needed. ‘<samp>F</samp>’ behaves like a float. For example, </p> <div class="example"> <pre class="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); mp_limb_t l; gmp_printf ("limb %Mu\n", l); const mp_limb_t *ptr; mp_size_t size; gmp_printf ("limb array %Nx\n", ptr, size); </pre></div> <p>For ‘<samp>N</samp>’ the limbs are expected least significant first, as per the <code>mpn</code> functions (see <a href="Low_002dlevel-Functions.html#Low_002dlevel-Functions">Low-level Functions</a>). A negative size can be given to print the value as a negative. </p> <p>All the standard C <code>printf</code> types behave the same as the C library <code>printf</code>, and can be freely intermixed with the GMP extensions. In the current implementation the standard parts of the format string are simply handed to <code>printf</code> and only the GMP extensions handled directly. </p> <p>The flags accepted are as follows. GLIBC style ‘<samp>'</samp>’ is only for the standard C types (not the GMP types), and only if the C library supports it. </p> <blockquote> <table> <tr><td><code>0</code></td><td>pad with zeros (rather than spaces)</td></tr> <tr><td><code>#</code></td><td>show the base with ‘<samp>0x</samp>’, ‘<samp>0X</samp>’ or ‘<samp>0</samp>’</td></tr> <tr><td><code>+</code></td><td>always show a sign</td></tr> <tr><td>(space)</td><td>show a space or a ‘<samp>-</samp>’ sign</td></tr> <tr><td><code>'</code></td><td>group digits, GLIBC style (not GMP types)</td></tr> </table> </blockquote> <p>The optional width and precision can be given as a number within the format string, or as a ‘<samp>*</samp>’ to take an extra parameter of type <code>int</code>, the same as the standard <code>printf</code>. </p> <p>The standard types accepted are as follows. ‘<samp>h</samp>’ and ‘<samp>l</samp>’ are portable, the rest will depend on the compiler (or include files) for the type and the C library for the output. </p> <blockquote> <table> <tr><td><code>h</code></td><td><code>short</code></td></tr> <tr><td><code>hh</code></td><td><code>char</code></td></tr> <tr><td><code>j</code></td><td><code>intmax_t</code> or <code>uintmax_t</code></td></tr> <tr><td><code>l</code></td><td><code>long</code> or <code>wchar_t</code></td></tr> <tr><td><code>ll</code></td><td><code>long long</code></td></tr> <tr><td><code>L</code></td><td><code>long double</code></td></tr> <tr><td><code>q</code></td><td><code>quad_t</code> or <code>u_quad_t</code></td></tr> <tr><td><code>t</code></td><td><code>ptrdiff_t</code></td></tr> <tr><td><code>z</code></td><td><code>size_t</code></td></tr> </table> </blockquote> <p>The GMP types are </p> <blockquote> <table> <tr><td><code>F</code></td><td><code>mpf_t</code>, float conversions</td></tr> <tr><td><code>Q</code></td><td><code>mpq_t</code>, integer conversions</td></tr> <tr><td><code>M</code></td><td><code>mp_limb_t</code>, integer conversions</td></tr> <tr><td><code>N</code></td><td><code>mp_limb_t</code> array, integer conversions</td></tr> <tr><td><code>Z</code></td><td><code>mpz_t</code>, integer conversions</td></tr> </table> </blockquote> <p>The conversions accepted are as follows. ‘<samp>a</samp>’ and ‘<samp>A</samp>’ are always supported for <code>mpf_t</code> but depend on the C library for standard C float types. ‘<samp>m</samp>’ and ‘<samp>p</samp>’ depend on the C library. </p> <blockquote> <table> <tr><td><code>a</code> <code>A</code></td><td>hex floats, C99 style</td></tr> <tr><td><code>c</code></td><td>character</td></tr> <tr><td><code>d</code></td><td>decimal integer</td></tr> <tr><td><code>e</code> <code>E</code></td><td>scientific format float</td></tr> <tr><td><code>f</code></td><td>fixed point float</td></tr> <tr><td><code>i</code></td><td>same as <code>d</code></td></tr> <tr><td><code>g</code> <code>G</code></td><td>fixed or scientific float</td></tr> <tr><td><code>m</code></td><td><code>strerror</code> string, GLIBC style</td></tr> <tr><td><code>n</code></td><td>store characters written so far</td></tr> <tr><td><code>o</code></td><td>octal integer</td></tr> <tr><td><code>p</code></td><td>pointer</td></tr> <tr><td><code>s</code></td><td>string</td></tr> <tr><td><code>u</code></td><td>unsigned integer</td></tr> <tr><td><code>x</code> <code>X</code></td><td>hex integer</td></tr> </table> </blockquote> <p>‘<samp>o</samp>’, ‘<samp>x</samp>’ and ‘<samp>X</samp>’ are unsigned for the standard C types, but for types ‘<samp>Z</samp>’, ‘<samp>Q</samp>’ and ‘<samp>N</samp>’ they are signed. ‘<samp>u</samp>’ is not meaningful for ‘<samp>Z</samp>’, ‘<samp>Q</samp>’ and ‘<samp>N</samp>’. </p> <p>‘<samp>M</samp>’ is a proxy for the C library ‘<samp>l</samp>’ or ‘<samp>L</samp>’, according to the size of <code>mp_limb_t</code>. Unsigned conversions will be usual, but a signed conversion can be used and will interpret the value as a twos complement negative. </p> <p>‘<samp>n</samp>’ can be used with any type, even the GMP types. </p> <p>Other types or conversions that might be accepted by the C library <code>printf</code> cannot be used through <code>gmp_printf</code>, this includes for instance extensions registered with GLIBC <code>register_printf_function</code>. Also currently there’s no support for POSIX ‘<samp>$</samp>’ style numbered arguments (perhaps this will be added in the future). </p> <p>The precision field has its usual meaning for integer ‘<samp>Z</samp>’ and float ‘<samp>F</samp>’ types, but is currently undefined for ‘<samp>Q</samp>’ and should not be used with that. </p> <p><code>mpf_t</code> conversions only ever generate as many digits as can be accurately represented by the operand, the same as <code>mpf_get_str</code> does. Zeros will be used if necessary to pad to the requested precision. This happens even for an ‘<samp>f</samp>’ conversion of an <code>mpf_t</code> which is an integer, for instance <em>2^1024<!-- /@w --></em> in an <code>mpf_t</code> of 128 bits precision will only produce about 40 digits, then pad with zeros to the decimal point. An empty precision field like ‘<samp>%.Fe</samp>’ or ‘<samp>%.Ff</samp>’ can be used to specifically request just the significant digits. Without any dot and thus no precision field, a precision value of 6 will be used. Note that these rules mean that ‘<samp>%Ff</samp>’, ‘<samp>%.Ff</samp>’, and ‘<samp>%.0Ff</samp>’ will all be different. </p> <p>The decimal point character (or string) is taken from the current locale settings on systems which provide <code>localeconv</code> (see <a href="http://www.gnu.org/software/libc/manual/html_node/Locales.html#Locales">Locales and Internationalization</a> in <cite>The GNU C Library Reference Manual</cite>). The C library will normally do the same for standard float output. </p> <p>The format string is only interpreted as plain <code>char</code>s, multibyte characters are not recognised. Perhaps this will change in the future. </p> <hr> <div class="header"> <p> Next: <a href="Formatted-Output-Functions.html#Formatted-Output-Functions" accesskey="n" rel="next">Formatted Output Functions</a>, Previous: <a href="Formatted-Output.html#Formatted-Output" accesskey="p" rel="prev">Formatted Output</a>, Up: <a href="Formatted-Output.html#Formatted-Output" accesskey="u" rel="up">Formatted Output</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> </div> </body> </html>