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<html xmlns:cf="http://docbook.sourceforge.net/xmlns/chunkfast/1.0"><head><meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"><title>Numerical Definitions</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.0"><link rel="start" href="index.html" title="GLib Reference Manual"><link rel="up" href="glib-fundamentals.html" title="GLib Fundamentals"><link rel="prev" href="glib-Byte-Order-Macros.html" title="Byte Order Macros"><link rel="next" href="glib-Miscellaneous-Macros.html" title="Miscellaneous Macros"><meta name="generator" content="GTK-Doc V1.4 (XML mode)"><link rel="stylesheet" href="style.css" type="text/css"><link rel="chapter" href="glib.html" title="GLib Overview"><link rel="chapter" href="glib-fundamentals.html" title="GLib Fundamentals"><link rel="chapter" href="glib-core.html" title="GLib Core Application Support"><link rel="chapter" href="glib-utilities.html" title="GLib Utilities"><link rel="chapter" href="glib-data-types.html" title="GLib Data Types"><link rel="chapter" href="tools.html" title="GLib Tools"><link rel="index" href="ix01.html" title="Index"><link rel="index" href="ix02.html" title="Index of deprecated symbols"><link rel="index" href="ix03.html" title="Index of new symbols in 2.2"><link rel="index" href="ix04.html" title="Index of new symbols in 2.4"><link rel="index" href="ix05.html" title="Index of new symbols in 2.6"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><table class="navigation" width="100%" summary="Navigation header" cellpadding="2" cellspacing="2"><tr valign="middle"><td><a accesskey="p" href="glib-Byte-Order-Macros.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td><td><a accesskey="u" href="glib-fundamentals.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td><td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td><th width="100%" align="center">GLib Reference Manual</th><td><a accesskey="n" href="glib-Miscellaneous-Macros.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td></tr></table><div class="refentry" lang="en"><a name="glib-Numerical-Definitions"></a><div class="titlepage"></div><div class="refnamediv"><table width="100%"><tr><td valign="top"><h2><span class="refentrytitle">Numerical Definitions</span></h2><p>Numerical Definitions — mathematical constants, and floating point decomposition.</p></td><td valign="top" align="right"></td></tr></table></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">#include <glib.h>#define <a href="glib-Numerical-Definitions.html#G-IEEE754-FLOAT-BIAS:CAPS">G_IEEE754_FLOAT_BIAS</a>#define <a href="glib-Numerical-Definitions.html#G-IEEE754-DOUBLE-BIAS:CAPS">G_IEEE754_DOUBLE_BIAS</a>union <a href="glib-Numerical-Definitions.html#GFloatIEEE754">GFloatIEEE754</a>;union <a href="glib-Numerical-Definitions.html#GDoubleIEEE754">GDoubleIEEE754</a>;#define <a href="glib-Numerical-Definitions.html#G-E:CAPS">G_E</a>#define <a href="glib-Numerical-Definitions.html#G-LN2:CAPS">G_LN2</a>#define <a href="glib-Numerical-Definitions.html#G-LN10:CAPS">G_LN10</a>#define <a href="glib-Numerical-Definitions.html#G-PI:CAPS">G_PI</a>#define <a href="glib-Numerical-Definitions.html#G-PI-2:CAPS">G_PI_2</a>#define <a href="glib-Numerical-Definitions.html#G-PI-4:CAPS">G_PI_4</a>#define <a href="glib-Numerical-Definitions.html#G-SQRT2:CAPS">G_SQRT2</a>#define <a href="glib-Numerical-Definitions.html#G-LOG-2-BASE-10:CAPS">G_LOG_2_BASE_10</a></pre></div><div class="refsect1" lang="en"><a name="id2837192"></a><h2>Description</h2><p>GLib offers mathematical constants such as <a href="glib-Numerical-Definitions.html#G-PI:CAPS"><span class="type">G_PI</span></a> for the value of pi;many platforms have these in the C library, but some don't, the GLibversions always exist.</p><p>The <a href="glib-Numerical-Definitions.html#GFloatIEEE754"><span class="type">GFloatIEEE754</span></a> and <a href="glib-Numerical-Definitions.html#GDoubleIEEE754"><span class="type">GDoubleIEEE754</span></a> unions are used to access the sign, mantissa and exponent of IEEE floats and doubles. These unions are defined as appropriate for a given platform. IEEE floats and doubles are supported (used for storage) by at least Intel, PPC and Sparc, for reference: <a href="http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html" target="_top">http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html</a></p></div><div class="refsect1" lang="en"><a name="id2837245"></a><h2>Details</h2><div class="refsect2" lang="en"><a name="id2837250"></a><h3><a name="G-IEEE754-FLOAT-BIAS:CAPS"></a>G_IEEE754_FLOAT_BIAS</h3><a class="indexterm" name="id2837261"></a><pre class="programlisting">#define G_IEEE754_FLOAT_BIAS (127)</pre><p>See <a href="http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html" target="_top">http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html</a></p></div><hr><div class="refsect2" lang="en"><a name="id2837285"></a><h3><a name="G-IEEE754-DOUBLE-BIAS:CAPS"></a>G_IEEE754_DOUBLE_BIAS</h3><a class="indexterm" name="id2837295"></a><pre class="programlisting">#define G_IEEE754_DOUBLE_BIAS (1023)</pre><p>See <a href="http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html" target="_top">http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html</a></p></div><hr><div class="refsect2" lang="en"><a name="id2837319"></a><h3><a name="GFloatIEEE754"></a>union GFloatIEEE754</h3><a class="indexterm" name="id2837330"></a><pre class="programlisting">union GFloatIEEE754{ gfloat v_float; struct { guint mantissa : 23; guint biased_exponent : 8; guint sign : 1; } mpn;};</pre><p>The <a href="glib-Numerical-Definitions.html#GFloatIEEE754"><span class="type">GFloatIEEE754</span></a> and <a href="glib-Numerical-Definitions.html#GDoubleIEEE754"><span class="type">GDoubleIEEE754</span></a> unions are used to access the sign, mantissa and exponent of IEEE floats and doubles. These unions are defined as appropriate for a given platform. IEEE floats and doubles are supported (used for storage) by at least Intel, PPC and Sparc, for reference: <a href="http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html" target="_top">http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html</a></p></div><hr><div class="refsect2" lang="en"><a name="id2837376"></a><h3><a name="GDoubleIEEE754"></a>union GDoubleIEEE754</h3><a class="indexterm" name="id2837387"></a><pre class="programlisting">union GDoubleIEEE754{ gdouble v_double; struct { guint mantissa_low : 32; guint mantissa_high : 20; guint biased_exponent : 11; guint sign : 1; } mpn;};</pre><p>The <a href="glib-Numerical-Definitions.html#GFloatIEEE754"><span class="type">GFloatIEEE754</span></a> and <a href="glib-Numerical-Definitions.html#GDoubleIEEE754"><span class="type">GDoubleIEEE754</span></a> unions are used to access the sign, mantissa and exponent of IEEE floats and doubles. These unions are defined as appropriate for a given platform. IEEE floats and doubles are supported (used for storage) by at least Intel, PPC and Sparc, for reference: <a href="http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html" target="_top">http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html</a></p></div><hr><div class="refsect2" lang="en"><a name="id2837434"></a><h3><a name="G-E:CAPS"></a>G_E</h3><a class="indexterm" name="id2837444"></a><pre class="programlisting">#define G_E 2.7182818284590452353602874713526624977572470937000</pre><p>The base of natural logarithms.</p></div><hr><div class="refsect2" lang="en"><a name="id2837460"></a><h3><a name="G-LN2:CAPS"></a>G_LN2</h3><a class="indexterm" name="id2837470"></a><pre class="programlisting">#define G_LN2 0.69314718055994530941723212145817656807550013436026</pre><p>The natural logarithm of 2.</p></div><hr><div class="refsect2" lang="en"><a name="id2837486"></a><h3><a name="G-LN10:CAPS"></a>G_LN10</h3><a class="indexterm" name="id2837496"></a><pre class="programlisting">#define G_LN10 2.3025850929940456840179914546843642076011014886288</pre><p>The natural logarithm of 10.</p></div><hr><div class="refsect2" lang="en"><a name="id2837513"></a><h3><a name="G-PI:CAPS"></a>G_PI</h3><a class="indexterm" name="id2837523"></a><pre class="programlisting">#define G_PI 3.1415926535897932384626433832795028841971693993751</pre><p>The value of pi (ratio of circle's circumference to its diameter).</p></div><hr><div class="refsect2" lang="en"><a name="id2837540"></a><h3><a name="G-PI-2:CAPS"></a>G_PI_2</h3><a class="indexterm" name="id2837551"></a><pre class="programlisting">#define G_PI_2 1.5707963267948966192313216916397514420985846996876</pre><p>Pi divided by 2.</p></div><hr><div class="refsect2" lang="en"><a name="id2837567"></a><h3><a name="G-PI-4:CAPS"></a>G_PI_4</h3><a class="indexterm" name="id2837577"></a><pre class="programlisting">#define G_PI_4 0.78539816339744830961566084581987572104929234984378</pre><p>Pi divided by 4.</p></div><hr><div class="refsect2" lang="en"><a name="id2837593"></a><h3><a name="G-SQRT2:CAPS"></a>G_SQRT2</h3><a class="indexterm" name="id2837603"></a><pre class="programlisting">#define G_SQRT2 1.4142135623730950488016887242096980785696718753769</pre><p>The square root of two.</p></div><hr><div class="refsect2" lang="en"><a name="id2837619"></a><h3><a name="G-LOG-2-BASE-10:CAPS"></a>G_LOG_2_BASE_10</h3><a class="indexterm" name="id2837631"></a><pre class="programlisting">#define G_LOG_2_BASE_10 (0.30102999566398119521)</pre><p>Used for fooling around with float formats, see <a href="http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html" target="_top">http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html</a></p></div></div><div class="refsect1" lang="en"><a name="id2837656"></a><h2>See Also</h2><p><a href="http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html" target="_top">http://cch.loria.fr/documentation/IEEE754/numerical_comp_guide/ncg_math.doc.html</a></p></div></div><table class="navigation" width="100%" summary="Navigation footer" cellpadding="2" cellspacing="0"><tr valign="middle"><td align="left"><a accesskey="p" href="glib-Byte-Order-Macros.html"><b><< Byte Order Macros</b></a></td><td align="right"><a accesskey="n" href="glib-Miscellaneous-Macros.html"><b>Miscellaneous Macros >></b></a></td></tr></table></body></html>?? 快捷鍵說明
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