1
2// Copyright (c) 2011 John Maddock
3// Use, modification and distribution are subject to the
4// Boost Software License, Version 1.0. (See accompanying file
5// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6
7#ifndef BOOST_MATH_TOOLS_BIG_CONSTANT_HPP
8#define BOOST_MATH_TOOLS_BIG_CONSTANT_HPP
9
10#include <boost/math/tools/config.hpp>
11#ifndef BOOST_MATH_NO_LEXICAL_CAST
12#include <boost/lexical_cast.hpp>
13#endif
14#include <boost/type_traits/is_constructible.hpp>
15#include <boost/type_traits/is_convertible.hpp>
16#include <boost/type_traits/is_floating_point.hpp>
17
18namespace boost{ namespace math{
19
20namespace tools{
21
22template <class T>
23struct numeric_traits : public std::numeric_limits< T > {};
24
25#ifdef BOOST_MATH_USE_FLOAT128
26typedef __float128 largest_float;
27#define BOOST_MATH_LARGEST_FLOAT_C(x) x##Q
28template <>
29struct numeric_traits<__float128>
30{
31 static const int digits = 113;
32 static const int digits10 = 33;
33 static const int max_exponent = 16384;
34 static const bool is_specialized = true;
35};
36#else
37typedef long double largest_float;
38#define BOOST_MATH_LARGEST_FLOAT_C(x) x##L
39#endif
40
41template <class T>
42inline BOOST_CONSTEXPR_OR_CONST T make_big_value(largest_float v, const char*, boost::true_type const&, boost::false_type const&) BOOST_MATH_NOEXCEPT(T)
43{
44 return static_cast<T>(v);
45}
46template <class T>
47inline BOOST_CONSTEXPR_OR_CONST T make_big_value(largest_float v, const char*, boost::true_type const&, boost::true_type const&) BOOST_MATH_NOEXCEPT(T)
48{
49 return static_cast<T>(v);
50}
51#ifndef BOOST_MATH_NO_LEXICAL_CAST
52template <class T>
53inline T make_big_value(largest_float, const char* s, boost::false_type const&, boost::false_type const&)
54{
55 return boost::lexical_cast<T>(s);
56}
57#endif
58template <class T>
59inline BOOST_MATH_CONSTEXPR T make_big_value(largest_float, const char* s, boost::false_type const&, boost::true_type const&) BOOST_MATH_NOEXCEPT(T)
60{
61 return T(s);
62}
63
64//
65// For constants which might fit in a long double (if it's big enough):
66//
67#define BOOST_MATH_BIG_CONSTANT(T, D, x)\
68 boost::math::tools::make_big_value<T>(\
69 BOOST_MATH_LARGEST_FLOAT_C(x), \
70 BOOST_STRINGIZE(x), \
71 boost::integral_constant<bool, (boost::is_convertible<boost::math::tools::largest_float, T>::value) && \
72 ((D <= boost::math::tools::numeric_traits<boost::math::tools::largest_float>::digits) \
73 || boost::is_floating_point<T>::value \
74 || (boost::math::tools::numeric_traits<T>::is_specialized && \
75 (boost::math::tools::numeric_traits<T>::digits10 <= boost::math::tools::numeric_traits<boost::math::tools::largest_float>::digits10))) >(), \
76 boost::is_constructible<T, const char*>())
77//
78// For constants too huge for any conceivable long double (and which generate compiler errors if we try and declare them as such):
79//
80#define BOOST_MATH_HUGE_CONSTANT(T, D, x)\
81 boost::math::tools::make_big_value<T>(0.0L, BOOST_STRINGIZE(x), \
82 boost::integral_constant<bool, boost::is_floating_point<T>::value || (boost::math::tools::numeric_traits<T>::is_specialized && boost::math::tools::numeric_traits<T>::max_exponent <= boost::math::tools::numeric_traits<boost::math::tools::largest_float>::max_exponent && boost::math::tools::numeric_traits<T>::digits <= boost::math::tools::numeric_traits<boost::math::tools::largest_float>::digits)>(), \
83 boost::is_constructible<T, const char*>())
84
85}}} // namespaces
86
87#endif
88
89

source code of include/boost/math/tools/big_constant.hpp