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200 lines
9.4 KiB
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200 lines
9.4 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This manual describes how to install and use the GNU multiple precision
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arithmetic library, version 6.1.0.
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Copyright 1991, 1993-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document under
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the terms of the GNU Free Documentation License, Version 1.3 or any later
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version published by the Free Software Foundation; with no Invariant Sections,
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with the Front-Cover Texts being "A GNU Manual", and with the Back-Cover
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Texts being "You have freedom to copy and modify this GNU Manual, like GNU
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software". A copy of the license is included in
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GNU Free Documentation License. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Integer Special Functions (GNU MP 6.1.0)</title>
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<meta name="description" content="How to install and use the GNU multiple precision arithmetic library, version 6.1.0.">
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<meta name="keywords" content="Integer Special Functions (GNU MP 6.1.0)">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="Integer-Functions.html#Integer-Functions" rel="up" title="Integer Functions">
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<link href="Rational-Number-Functions.html#Rational-Number-Functions" rel="next" title="Rational Number Functions">
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<link href="Miscellaneous-Integer-Functions.html#Miscellaneous-Integer-Functions" rel="prev" title="Miscellaneous Integer Functions">
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</style>
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</head>
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<body lang="en">
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<a name="Integer-Special-Functions"></a>
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<div class="header">
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<p>
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Previous: <a href="Miscellaneous-Integer-Functions.html#Miscellaneous-Integer-Functions" accesskey="p" rel="prev">Miscellaneous Integer Functions</a>, Up: <a href="Integer-Functions.html#Integer-Functions" accesskey="u" rel="up">Integer Functions</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Special-Functions"></a>
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<h3 class="section">5.16 Special Functions</h3>
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<a name="index-Special-integer-functions"></a>
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<a name="index-Integer-special-functions"></a>
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<p>The functions in this section are for various special purposes. Most
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applications will not need them.
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</p>
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<dl>
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<dt><a name="index-mpz_005farray_005finit"></a>Function: <em>void</em> <strong>mpz_array_init</strong> <em>(mpz_t <var>integer_array</var>, mp_size_t <var>array_size</var>, <span class="nolinebreak">mp_size_t</span> <var><span class="nolinebreak">fixed_num_bits</span></var><!-- /@w -->)</em></dt>
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<dd><p><strong>This is an obsolete function. Do not use it.</strong>
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</p></dd></dl>
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<dl>
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<dt><a name="index-_005fmpz_005frealloc"></a>Function: <em>void *</em> <strong>_mpz_realloc</strong> <em>(mpz_t <var>integer</var>, mp_size_t <var>new_alloc</var>)</em></dt>
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<dd><p>Change the space for <var>integer</var> to <var>new_alloc</var> limbs. The value in
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<var>integer</var> is preserved if it fits, or is set to 0 if not. The return
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value is not useful to applications and should be ignored.
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</p>
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<p><code>mpz_realloc2</code> is the preferred way to accomplish allocation changes like
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this. <code>mpz_realloc2</code> and <code>_mpz_realloc</code> are the same except that
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<code>_mpz_realloc</code> takes its size in limbs.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpz_005fgetlimbn"></a>Function: <em>mp_limb_t</em> <strong>mpz_getlimbn</strong> <em>(const mpz_t <var>op</var>, mp_size_t <var>n</var>)</em></dt>
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<dd><p>Return limb number <var>n</var> from <var>op</var>. The sign of <var>op</var> is ignored,
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just the absolute value is used. The least significant limb is number 0.
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</p>
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<p><code>mpz_size</code> can be used to find how many limbs make up <var>op</var>.
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<code>mpz_getlimbn</code> returns zero if <var>n</var> is outside the range 0 to
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<code>mpz_size(<var>op</var>)-1</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpz_005fsize"></a>Function: <em>size_t</em> <strong>mpz_size</strong> <em>(const mpz_t <var>op</var>)</em></dt>
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<dd><p>Return the size of <var>op</var> measured in number of limbs. If <var>op</var> is zero,
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the returned value will be zero.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpz_005flimbs_005fread"></a>Function: <em>const mp_limb_t *</em> <strong>mpz_limbs_read</strong> <em>(const mpz_t <var>x</var>)</em></dt>
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<dd><p>Return a pointer to the limb array representing the absolute value of <var>x</var>.
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The size of the array is <code>mpz_size(<var>x</var>)</code>. Intended for read access
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only.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpz_005flimbs_005fwrite"></a>Function: <em>mp_limb_t *</em> <strong>mpz_limbs_write</strong> <em>(mpz_t <var>x</var>, mp_size_t <var>n</var>)</em></dt>
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<dt><a name="index-mpz_005flimbs_005fmodify"></a>Function: <em>mp_limb_t *</em> <strong>mpz_limbs_modify</strong> <em>(mpz_t <var>x</var>, mp_size_t <var>n</var>)</em></dt>
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<dd><p>Return a pointer to the limb array, intended for write access. The array is
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reallocated as needed, to make room for <var>n</var> limbs. Requires <em><var>n</var>
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> 0</em>. The <code>mpz_limbs_modify</code> function returns an array that holds the old
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absolute value of <var>x</var>, while <code>mpz_limbs_write</code> may destroy the old
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value and return an array with unspecified contents.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpz_005flimbs_005ffinish"></a>Function: <em>void</em> <strong>mpz_limbs_finish</strong> <em>(mpz_t <var>x</var>, mp_size_t <var>s</var>)</em></dt>
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<dd><p>Updates the internal size field of <var>x</var>. Used after writing to the limb
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array pointer returned by <code>mpz_limbs_write</code> or <code>mpz_limbs_modify</code> is
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completed. The array should contain <em>abs(<var>s</var>)</em> valid limbs,
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representing the new absolute value for <var>x</var>, and the sign of <var>x</var> is
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taken from the sign of <var>s</var>. This function never reallocates <var>x</var>, so
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the limb pointer remains valid.
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</p></dd></dl>
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<div class="example">
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<pre class="example">void foo (mpz_t x)
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{
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mp_size_t n, i;
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mp_limb_t *xp;
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n = mpz_size (x);
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xp = mpz_limbs_modify (x, 2*n);
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for (i = 0; i < n; i++)
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xp[n+i] = xp[n-1-i];
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mpz_limbs_finish (x, mpz_sgn (x) < 0 ? - 2*n : 2*n);
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}
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</pre></div>
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<dl>
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<dt><a name="index-mpz_005froinit_005fn"></a>Function: <em>mpz_srcptr</em> <strong>mpz_roinit_n</strong> <em>(mpz_t <var>x</var>, const mp_limb_t *<var>xp</var>, mp_size_t <var>xs</var>)</em></dt>
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<dd><p>Special initialization of <var>x</var>, using the given limb array and size.
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<var>x</var> should be treated as read-only: it can be passed safely as input to
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any mpz function, but not as an output. The array <var>xp</var> must point to at
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least a readable limb, its size is
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<em>abs(<var>xs</var>)</em>, and the sign of <var>x</var> is the sign of <var>xs</var>. For
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convenience, the function returns <var>x</var>, but cast to a const pointer type.
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</p></dd></dl>
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<div class="example">
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<pre class="example">void foo (mpz_t x)
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{
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static const mp_limb_t y[3] = { 0x1, 0x2, 0x3 };
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mpz_t tmp;
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mpz_add (x, x, mpz_roinit_n (tmp, y, 3));
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}
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</pre></div>
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<dl>
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<dt><a name="index-MPZ_005fROINIT_005fN"></a>Macro: <em>mpz_t</em> <strong>MPZ_ROINIT_N</strong> <em>(mp_limb_t *<var>xp</var>, mp_size_t <var>xs</var>)</em></dt>
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<dd><p>This macro expands to an initializer which can be assigned to an mpz_t
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variable. The limb array <var>xp</var> must point to at least a readable limb,
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moreover, unlike the <code>mpz_roinit_n</code> function, the array must be
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normalized: if <var>xs</var> is non-zero, then
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<code><var>xp</var>[<em>abs(<var>xs</var>)-1</em>]</code> must be non-zero. Intended
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primarily for constant values. Using it for non-constant values requires a C
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compiler supporting C99.
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</p></dd></dl>
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<div class="example">
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<pre class="example">void foo (mpz_t x)
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{
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static const mp_limb_t ya[3] = { 0x1, 0x2, 0x3 };
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static const mpz_t y = MPZ_ROINIT_N ((mp_limb_t *) ya, 3);
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mpz_add (x, x, y);
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}
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</pre></div>
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<hr>
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<div class="header">
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<p>
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Previous: <a href="Miscellaneous-Integer-Functions.html#Miscellaneous-Integer-Functions" accesskey="p" rel="prev">Miscellaneous Integer Functions</a>, Up: <a href="Integer-Functions.html#Integer-Functions" accesskey="u" rel="up">Integer Functions</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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