Chris@16: 
Chris@16: //  Copyright (c) 2011 John Maddock
Chris@16: //  Use, modification and distribution are subject to the
Chris@16: //  Boost Software License, Version 1.0. (See accompanying file
Chris@16: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_MATH_TOOLS_BIG_CONSTANT_HPP
Chris@16: #define BOOST_MATH_TOOLS_BIG_CONSTANT_HPP
Chris@16: 
Chris@16: #include <boost/math/tools/config.hpp>
Chris@16: #ifndef BOOST_MATH_NO_LEXICAL_CAST
Chris@16: #include <boost/lexical_cast.hpp>
Chris@16: #endif
Chris@16: #include <boost/type_traits/is_convertible.hpp>
Chris@16: 
Chris@16: namespace boost{ namespace math{ 
Chris@16: 
Chris@16: namespace tools{
Chris@16: 
Chris@16: template <class T>
Chris@101: struct numeric_traits : public std::numeric_limits< T > {};
Chris@101: 
Chris@101: #ifdef BOOST_MATH_USE_FLOAT128
Chris@101: typedef __float128 largest_float;
Chris@101: #define BOOST_MATH_LARGEST_FLOAT_C(x) x##Q
Chris@101: template <>
Chris@101: struct numeric_traits<__float128>
Chris@101: {
Chris@101:    static const int digits = 113;
Chris@101:    static const int digits10 = 34;
Chris@101:    static const int max_exponent = 16384;
Chris@101:    static const bool is_specialized = true;
Chris@101: };
Chris@101: #else
Chris@101: typedef long double largest_float;
Chris@101: #define BOOST_MATH_LARGEST_FLOAT_C(x) x##L
Chris@101: #endif
Chris@101: 
Chris@101: template <class T>
Chris@101: inline BOOST_CONSTEXPR_OR_CONST T make_big_value(largest_float v, const char*, mpl::true_ const&, mpl::false_ const&)
Chris@16: {
Chris@16:    return static_cast<T>(v);
Chris@16: }
Chris@16: template <class T>
Chris@101: inline BOOST_CONSTEXPR_OR_CONST T make_big_value(largest_float v, const char*, mpl::true_ const&, mpl::true_ const&)
Chris@16: {
Chris@16:    return static_cast<T>(v);
Chris@16: }
Chris@16: #ifndef BOOST_MATH_NO_LEXICAL_CAST
Chris@16: template <class T>
Chris@101: inline T make_big_value(largest_float, const char* s, mpl::false_ const&, mpl::false_ const&)
Chris@16: {
Chris@16:    return boost::lexical_cast<T>(s);
Chris@16: }
Chris@16: #endif
Chris@16: template <class T>
Chris@101: inline BOOST_CONSTEXPR const char* make_big_value(largest_float, const char* s, mpl::false_ const&, mpl::true_ const&)
Chris@16: {
Chris@16:    return s;
Chris@16: }
Chris@16: 
Chris@16: //
Chris@16: // For constants which might fit in a long double (if it's big enough):
Chris@16: //
Chris@16: #define BOOST_MATH_BIG_CONSTANT(T, D, x)\
Chris@16:    boost::math::tools::make_big_value<T>(\
Chris@101:       BOOST_MATH_LARGEST_FLOAT_C(x), \
Chris@16:       BOOST_STRINGIZE(x), \
Chris@101:       mpl::bool_< (is_convertible<boost::math::tools::largest_float, T>::value) && \
Chris@101:       ((D <= boost::math::tools::numeric_traits<boost::math::tools::largest_float>::digits) \
Chris@16:           || is_floating_point<T>::value \
Chris@101:           || (boost::math::tools::numeric_traits<T>::is_specialized && \
Chris@101:           (boost::math::tools::numeric_traits<T>::digits10 <= boost::math::tools::numeric_traits<boost::math::tools::largest_float>::digits10))) >(), \
Chris@16:       boost::is_convertible<const char*, T>())
Chris@16: //
Chris@16: // For constants too huge for any conceivable long double (and which generate compiler errors if we try and declare them as such):
Chris@16: //
Chris@16: #define BOOST_MATH_HUGE_CONSTANT(T, D, x)\
Chris@16:    boost::math::tools::make_big_value<T>(0.0L, BOOST_STRINGIZE(x), \
Chris@101:    mpl::bool_<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)>(), \
Chris@16:    boost::is_convertible<const char*, T>())
Chris@16: 
Chris@16: }}} // namespaces
Chris@16: 
Chris@16: #endif
Chris@16: