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26 <div class=
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"clear: both">
27 <a name=
"math_toolkit.specified_typedefs"></a><a class=
"link" href=
"specified_typedefs.html" title=
"Overview">Overview
</a>
28 </h2></div></div></div>
30 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>
31 provides
<span class=
"bold"><strong>optional
</strong></span> standardized floating-point
32 <code class=
"computeroutput"><span class=
"keyword">typedef
</span></code>s having
<span class=
"bold"><strong>specified
33 widths
</strong></span>. These are useful for writing portable code because they
34 should behave identically on all platforms. These
<code class=
"computeroutput"><span class=
"keyword">typedef
</span></code>s
35 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>.
38 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>
39 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>
40 and
<a href=
"http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1703.pdf" target=
"_top">N1703
</a>
41 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>.
44 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>
45 (would be in namespace
<code class=
"computeroutput"><span class=
"identifier">std
</span></code>
46 if eventually standardized).
49 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
50 fast types, and the corresponding maximum-width type. The
<code class=
"computeroutput"><span class=
"keyword">typedef
</span></code>s
51 are based on underlying built-in types such as
<code class=
"computeroutput"><span class=
"keyword">float
</span></code>,
52 <code class=
"computeroutput"><span class=
"keyword">double
</span></code>, or
<code class=
"computeroutput"><span class=
"keyword">long
</span>
53 <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
54 short float type
</a>, or based on other compiler-specific non-standardized
55 types such as
<code class=
"computeroutput"><span class=
"identifier">__float128
</span></code>. The
56 underlying types of these
<code class=
"computeroutput"><span class=
"keyword">typedef
</span></code>s
57 must conform with the corresponding specifications of binary16, binary32, binary64,
58 and binary128 in
<a href=
"http://en.wikipedia.org/wiki/IEEE_floating_point" target=
"_top">IEEE_floating_point
</a>
59 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>
60 <span class=
"special">==
</span> <span class=
"keyword">true
</span></code>.
63 The
128-bit floating-point type (of great interest in scientific and numeric
64 programming) is not required in the Boost header, and may not be supplied for
65 all platforms/compilers, because compiler support for a
128-bit floating-point
66 type is not mandated by either the C standard or the C++ standard.
69 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
70 a
<span class=
"bold"><strong>native
</strong></span> 128-bit type, and includes other
71 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>
72 that provide C++ quad support for
<a href=
"http://www.cplusplus.com/reference/cmath/" target=
"_top">C
73 math functions
</a> in
<code class=
"computeroutput"><span class=
"special"><</span><span class=
"identifier">cmath
</span><span class=
"special">></span></code>,
74 <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>,
75 <code class=
"computeroutput"><span class=
"special"><</span><span class=
"identifier">complex
</span><span class=
"special">></span></code>, and the available floating-point types.
78 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
79 this provides a thin wrapper selecting the appropriate
128-bit native type
80 from
<code class=
"computeroutput"><span class=
"identifier">cstdfloat
</span></code> if available,
81 or else a
128-bit multiprecision type.
84 See
<a class=
"link" href=
"examples.html#math_toolkit.examples.je_lambda">Jahnke-Emden-Lambda function
85 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>
86 function and a Boost.Math function to evaluate a moderately interesting function,
87 the
<a href=
"http://mathworld.wolfram.com/LambdaFunction.html" target=
"_top">Jahnke-Emden-Lambda
88 function
</a> and
<a class=
"link" href=
"examples.html#math_toolkit.examples.normal_table">normal
89 distribution
</a> as an example of a statistical distribution from Boost.Math.
92 <table xmlns:
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"100%"><tr>
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"left"></td>
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"right"><div class=
"copyright-footer">Copyright
© 2006-
2010,
2012-
2014 Nikhar Agrawal,
95 Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
96 Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan R
åde, Gautam Sewani,
97 Benjamin Sobotta, Thijs van den Berg, Daryle Walker and Xiaogang Zhang
<p>
98 Distributed under the Boost Software License, Version
1.0. (See accompanying
99 file LICENSE_1_0.txt or copy at
<a href=
"http://www.boost.org/LICENSE_1_0.txt" target=
"_top">http://www.boost.org/LICENSE_1_0.txt
</a>)
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