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- <div class="titlepage"><div><div><h2 class="title" style="clear: both">
- <a name="math_toolkit.specified_typedefs"></a><a class="link" href="specified_typedefs.html" title="Overview">Overview</a>
- </h2></div></div></div>
- <p>
- The header <code class="computeroutput"><span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">cstdfloat</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code>
- provides <span class="bold"><strong>optional</strong></span> standardized floating-point
- <code class="computeroutput"><span class="keyword">typedef</span></code>s having <span class="bold"><strong>specified
- widths</strong></span>. These are useful for writing portable code because they
- should behave identically on all platforms. These <code class="computeroutput"><span class="keyword">typedef</span></code>s
- are the floating-point analog of specified-width integers in <code class="computeroutput"><span class="special"><</span><span class="identifier">cstdint</span><span class="special">></span></code> and <code class="computeroutput"><span class="identifier">stdint</span><span class="special">.</span><span class="identifier">h</span></code>.
- </p>
- <p>
- The <code class="computeroutput"><span class="keyword">typedef</span></code>s are based on <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3626.pdf" target="_top">N3626</a>
- proposed for a new C++14 standard header <code class="computeroutput"><span class="special"><</span><span class="identifier">cstdfloat</span><span class="special">></span></code>
- and <a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1703.pdf" target="_top">N1703</a>
- proposed for a new C language standard header <code class="computeroutput"><span class="special"><</span><span class="identifier">stdfloat</span><span class="special">.</span><span class="identifier">h</span><span class="special">></span></code>.
- </p>
- <p>
- All <code class="computeroutput"><span class="keyword">typedef</span></code>s are in <code class="computeroutput"><span class="keyword">namespace</span> <span class="identifier">boost</span></code>
- (would be in namespace <code class="computeroutput"><span class="identifier">std</span></code>
- if eventually standardized).
- </p>
- <p>
- The <code class="computeroutput"><span class="keyword">typedef</span></code>s include <code class="computeroutput"><span class="identifier">float16_t</span><span class="special">,</span> <span class="identifier">float32_t</span><span class="special">,</span> <span class="identifier">float64_t</span><span class="special">,</span> <span class="identifier">float80_t</span><span class="special">,</span> <span class="identifier">float128_t</span></code>, their corresponding least and
- fast types, and the corresponding maximum-width type. The <code class="computeroutput"><span class="keyword">typedef</span></code>s
- are based on underlying built-in types such as <code class="computeroutput"><span class="keyword">float</span></code>,
- <code class="computeroutput"><span class="keyword">double</span></code>, or <code class="computeroutput"><span class="keyword">long</span>
- <span class="keyword">double</span></code>, or the proposed <a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2016.pdf" target="_top">N2016
- short float type</a>, or based on other compiler-specific non-standardized
- types such as <code class="computeroutput"><span class="identifier">__float128</span></code>. The
- underlying types of these <code class="computeroutput"><span class="keyword">typedef</span></code>s
- must conform with the corresponding specifications of binary16, binary32, binary64,
- and binary128 in <a href="http://en.wikipedia.org/wiki/IEEE_floating_point" target="_top">IEEE_floating_point</a>
- floating-point format, and <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><>::</span><span class="identifier">is_iec559</span>
- <span class="special">==</span> <span class="keyword">true</span></code>.
- </p>
- <p>
- The 128-bit floating-point type (of great interest in scientific and numeric
- programming) is not required in the Boost header, and may not be supplied for
- all platforms/compilers, because compiler support for a 128-bit floating-point
- type is not mandated by either the C standard or the C++ standard.
- </p>
- <p>
- If 128-bit floating-point is supported, then including <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">cstdfloat</span><span class="special">.</span><span class="identifier">hpp</span></code> provides
- a <span class="bold"><strong>native</strong></span> 128-bit type, and includes other
- headers in folder <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">math</span><span class="special">/</span><span class="identifier">cstdfloat</span></code>
- that provide C++ quad support for <a href="http://www.cplusplus.com/reference/cmath/" target="_top">C
- math functions</a> in <code class="computeroutput"><span class="special"><</span><span class="identifier">cmath</span><span class="special">></span></code>,
- <code class="computeroutput"><span class="special"><</span><span class="identifier">limits</span><span class="special">></span></code>, <code class="computeroutput"><span class="special"><</span><span class="identifier">iostream</span><span class="special">></span></code>,
- <code class="computeroutput"><span class="special"><</span><span class="identifier">complex</span><span class="special">></span></code>, and the available floating-point types.
- </p>
- <p>
- One can also, more robustly, include <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">multiprecision</span><span class="special">/</span><span class="identifier">float128</span><span class="special">.</span><span class="identifier">hpp</span></code> and
- this provides a thin wrapper selecting the appropriate 128-bit native type
- from <code class="computeroutput"><span class="identifier">cstdfloat</span></code> if available,
- or else a 128-bit multiprecision type.
- </p>
- <p>
- See <a class="link" href="examples.html#math_toolkit.examples.je_lambda">Jahnke-Emden-Lambda function
- example</a> for an example using both a <code class="computeroutput"><span class="special"><</span><span class="identifier">cmath</span><span class="special">></span></code>
- function and a Boost.Math function to evaluate a moderately interesting function,
- the <a href="http://mathworld.wolfram.com/LambdaFunction.html" target="_top">Jahnke-Emden-Lambda
- function</a> and <a class="link" href="examples.html#math_toolkit.examples.normal_table">normal
- distribution</a> as an example of a statistical distribution from Boost.Math.
- </p>
- </div>
- <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
- <td align="left"></td>
- <td align="right"><div class="copyright-footer">Copyright © 2006-2019 Nikhar
- Agrawal, Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos,
- Hubert Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Matthew Pulver, Johan
- Råde, Gautam Sewani, Benjamin Sobotta, Nicholas Thompson, Thijs van den Berg,
- Daryle Walker and Xiaogang Zhang<p>
- Distributed under the Boost Software License, Version 1.0. (See accompanying
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