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182 lines
7.8 KiB
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182 lines
7.8 KiB
HTML
4 years ago
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<!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>C++ Interface General (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="C++ Interface General (GNU MP 6.1.0)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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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="C_002b_002b-Class-Interface.html#C_002b_002b-Class-Interface" rel="up" title="C++ Class Interface">
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<link href="C_002b_002b-Interface-Integers.html#C_002b_002b-Interface-Integers" rel="next" title="C++ Interface Integers">
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<link href="C_002b_002b-Class-Interface.html#C_002b_002b-Class-Interface" rel="prev" title="C++ Class Interface">
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</style>
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</head>
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<body lang="en">
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<a name="C_002b_002b-Interface-General"></a>
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<div class="header">
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<p>
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Next: <a href="C_002b_002b-Interface-Integers.html#C_002b_002b-Interface-Integers" accesskey="n" rel="next">C++ Interface Integers</a>, Previous: <a href="C_002b_002b-Class-Interface.html#C_002b_002b-Class-Interface" accesskey="p" rel="prev">C++ Class Interface</a>, Up: <a href="C_002b_002b-Class-Interface.html#C_002b_002b-Class-Interface" accesskey="u" rel="up">C++ Class Interface</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="C_002b_002b-Interface-General-1"></a>
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<h3 class="section">12.1 C++ Interface General</h3>
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<p>All the C++ classes and functions are available with
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</p>
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<a name="index-gmpxx_002eh"></a>
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<div class="example">
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<pre class="example">#include <gmpxx.h>
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</pre></div>
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<p>Programs should be linked with the <samp>libgmpxx</samp> and <samp>libgmp</samp>
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libraries. For example,
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</p>
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<div class="example">
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<pre class="example">g++ mycxxprog.cc -lgmpxx -lgmp
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</pre></div>
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<p>The classes defined are
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</p>
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<dl>
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<dt><a name="index-mpz_005fclass"></a>Class: <strong>mpz_class</strong></dt>
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<dt><a name="index-mpq_005fclass"></a>Class: <strong>mpq_class</strong></dt>
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<dt><a name="index-mpf_005fclass"></a>Class: <strong>mpf_class</strong></dt>
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</dl>
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<p>The standard operators and various standard functions are overloaded to allow
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arithmetic with these classes. For example,
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</p>
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<div class="example">
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<pre class="example">int
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main (void)
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{
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mpz_class a, b, c;
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a = 1234;
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b = "-5678";
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c = a+b;
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cout << "sum is " << c << "\n";
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cout << "absolute value is " << abs(c) << "\n";
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return 0;
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}
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</pre></div>
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<p>An important feature of the implementation is that an expression like
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<code>a=b+c</code> results in a single call to the corresponding <code>mpz_add</code>,
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without using a temporary for the <code>b+c</code> part. Expressions which by their
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nature imply intermediate values, like <code>a=b*c+d*e</code>, still use temporaries
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though.
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</p>
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<p>The classes can be freely intermixed in expressions, as can the classes and
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the standard types <code>long</code>, <code>unsigned long</code> and <code>double</code>.
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Smaller types like <code>int</code> or <code>float</code> can also be intermixed, since
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C++ will promote them.
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</p>
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<p>Note that <code>bool</code> is not accepted directly, but must be explicitly cast to
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an <code>int</code> first. This is because C++ will automatically convert any
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pointer to a <code>bool</code>, so if GMP accepted <code>bool</code> it would make all
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sorts of invalid class and pointer combinations compile but almost certainly
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not do anything sensible.
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</p>
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<p>Conversions back from the classes to standard C++ types aren’t done
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automatically, instead member functions like <code>get_si</code> are provided (see
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the following sections for details).
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</p>
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<p>Also there are no automatic conversions from the classes to the corresponding
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GMP C types, instead a reference to the underlying C object can be obtained
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with the following functions,
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</p>
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<dl>
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<dt><a name="index-mpz_005fclass_003a_003aget_005fmpz_005ft"></a>Function: <em>mpz_t</em> <strong>mpz_class::get_mpz_t</strong> <em>()</em></dt>
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<dt><a name="index-mpq_005fclass_003a_003aget_005fmpq_005ft"></a>Function: <em>mpq_t</em> <strong>mpq_class::get_mpq_t</strong> <em>()</em></dt>
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<dt><a name="index-mpf_005fclass_003a_003aget_005fmpf_005ft"></a>Function: <em>mpf_t</em> <strong>mpf_class::get_mpf_t</strong> <em>()</em></dt>
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</dl>
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<p>These can be used to call a C function which doesn’t have a C++ class
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interface. For example to set <code>a</code> to the GCD of <code>b</code> and <code>c</code>,
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</p>
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<div class="example">
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<pre class="example">mpz_class a, b, c;
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...
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mpz_gcd (a.get_mpz_t(), b.get_mpz_t(), c.get_mpz_t());
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</pre></div>
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<p>In the other direction, a class can be initialized from the corresponding GMP
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C type, or assigned to if an explicit constructor is used. In both cases this
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makes a copy of the value, it doesn’t create any sort of association. For
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example,
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</p>
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<div class="example">
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<pre class="example">mpz_t z;
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// ... init and calculate z ...
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mpz_class x(z);
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mpz_class y;
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y = mpz_class (z);
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</pre></div>
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<p>There are no namespace setups in <samp>gmpxx.h</samp>, all types and functions are
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simply put into the global namespace. This is what <samp>gmp.h</samp> has done in
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the past, and continues to do for compatibility. The extras provided by
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<samp>gmpxx.h</samp> follow GMP naming conventions and are unlikely to clash with
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anything.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="C_002b_002b-Interface-Integers.html#C_002b_002b-Interface-Integers" accesskey="n" rel="next">C++ Interface Integers</a>, Previous: <a href="C_002b_002b-Class-Interface.html#C_002b_002b-Class-Interface" accesskey="p" rel="prev">C++ Class Interface</a>, Up: <a href="C_002b_002b-Class-Interface.html#C_002b_002b-Class-Interface" accesskey="u" rel="up">C++ Class Interface</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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