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The header <boost/cstdfloat.hpp>
provides optional standardized floating-point
typedefs having specified
widths. These are useful for writing portable code because they
should behave identically on all platforms. These typedefs
are the floating-point analog of specified-width integers in <cstdint> and stdint.h.
The typedefs are based on N3626
proposed for a new C++14 standard header <cstdfloat>
and N1703
proposed for a new C language standard header <stdfloat.h>.
All typedefs are in namespace boost
(would be in namespace std
if eventually standardized).
The typedefs include float16_t, float32_t, float64_t, float80_t, float128_t, their corresponding least and
fast types, and the corresponding maximum-width type. The typedefs
are based on underlying built-in types such as float,
double, or long
double, or the proposed N2016
short float type, or based on other compiler-specific non-standardized
types such as __float128. The
underlying types of these typedefs
must conform with the corresponding specifications of binary16, binary32, binary64,
and binary128 in IEEE_floating_point
floating-point format, and std::numeric_limits<>::is_iec559
== true.
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.
If 128-bit floating-point is supported, then including boost/cstdfloat.hpp provides
a native 128-bit type, and includes other
headers in folder boost/math/cstdfloat
that provide C++ quad support for C
math functions in <cmath>,
<limits>, <iostream>,
<complex>, and the available floating-point types.
One can also, more robustly, include boost/multiprecision/float128.hpp and
this provides a thin wrapper selecting the appropriate 128-bit native type
from cstdfloat if available,
or else a 128-bit multiprecision type.
See Jahnke-Emden-Lambda function
example for an example using both a <cmath>
function and a Boost.Math function to evaluate a moderately interesting function,
the Jahnke-Emden-Lambda
function and normal
distribution as an example of a statistical distribution from Boost.Math.