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123 lines
5.7 KiB
HTML
123 lines
5.7 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>Rational Conversions (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="Rational Conversions (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="Rational-Number-Functions.html#Rational-Number-Functions" rel="up" title="Rational Number Functions">
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<link href="Rational-Arithmetic.html#Rational-Arithmetic" rel="next" title="Rational Arithmetic">
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<link href="Initializing-Rationals.html#Initializing-Rationals" rel="prev" title="Initializing Rationals">
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<style type="text/css">
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a.summary-letter {text-decoration: none}
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blockquote.indentedblock {margin-right: 0em}
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blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
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blockquote.smallquotation {font-size: smaller}
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div.display {margin-left: 3.2em}
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div.example {margin-left: 3.2em}
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div.lisp {margin-left: 3.2em}
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div.smalldisplay {margin-left: 3.2em}
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kbd {font-style: oblique}
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pre.display {font-family: inherit}
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pre.format {font-family: inherit}
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pre.menu-comment {font-family: serif}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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pre.smalllisp {font-size: smaller}
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span.nolinebreak {white-space: nowrap}
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span.roman {font-family: initial; font-weight: normal}
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span.sansserif {font-family: sans-serif; font-weight: normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Rational-Conversions"></a>
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<div class="header">
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<p>
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Next: <a href="Rational-Arithmetic.html#Rational-Arithmetic" accesskey="n" rel="next">Rational Arithmetic</a>, Previous: <a href="Initializing-Rationals.html#Initializing-Rationals" accesskey="p" rel="prev">Initializing Rationals</a>, Up: <a href="Rational-Number-Functions.html#Rational-Number-Functions" accesskey="u" rel="up">Rational Number 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="Conversion-Functions-1"></a>
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<h3 class="section">6.2 Conversion Functions</h3>
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<a name="index-Rational-conversion-functions"></a>
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<a name="index-Conversion-functions-1"></a>
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<dl>
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<dt><a name="index-mpq_005fget_005fd"></a>Function: <em>double</em> <strong>mpq_get_d</strong> <em>(const mpq_t <var>op</var>)</em></dt>
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<dd><p>Convert <var>op</var> to a <code>double</code>, truncating if necessary (i.e. rounding
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towards zero).
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</p>
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<p>If the exponent from the conversion is too big or too small to fit a
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<code>double</code> then the result is system dependent. For too big an infinity is
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returned when available. For too small <em>0.0</em> is normally returned.
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Hardware overflow, underflow and denorm traps may or may not occur.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpq_005fset_005fd"></a>Function: <em>void</em> <strong>mpq_set_d</strong> <em>(mpq_t <var>rop</var>, double <var>op</var>)</em></dt>
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<dt><a name="index-mpq_005fset_005ff"></a>Function: <em>void</em> <strong>mpq_set_f</strong> <em>(mpq_t <var>rop</var>, const mpf_t <var>op</var>)</em></dt>
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<dd><p>Set <var>rop</var> to the value of <var>op</var>. There is no rounding, this conversion
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is exact.
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</p></dd></dl>
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<dl>
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<dt><a name="index-mpq_005fget_005fstr"></a>Function: <em>char *</em> <strong>mpq_get_str</strong> <em>(char *<var>str</var>, int <var>base</var>, const mpq_t <var>op</var>)</em></dt>
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<dd><p>Convert <var>op</var> to a string of digits in base <var>base</var>. The base may vary
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from 2 to 36. The string will be of the form ‘<samp>num/den</samp>’, or if the
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denominator is 1 then just ‘<samp>num</samp>’.
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</p>
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<p>If <var>str</var> is <code>NULL</code>, the result string is allocated using the current
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allocation function (see <a href="Custom-Allocation.html#Custom-Allocation">Custom Allocation</a>). The block will be
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<code>strlen(str)+1</code> bytes, that being exactly enough for the string and
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null-terminator.
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</p>
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<p>If <var>str</var> is not <code>NULL</code>, it should point to a block of storage large
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enough for the result, that being
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</p>
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<div class="example">
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<pre class="example">mpz_sizeinbase (mpq_numref(<var>op</var>), <var>base</var>)
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+ mpz_sizeinbase (mpq_denref(<var>op</var>), <var>base</var>) + 3
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</pre></div>
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<p>The three extra bytes are for a possible minus sign, possible slash, and the
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null-terminator.
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</p>
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<p>A pointer to the result string is returned, being either the allocated block,
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or the given <var>str</var>.
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</p></dd></dl>
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</body>
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</html>
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