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246 lines
11 KiB
246 lines
11 KiB
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// Copyright 2005-2009 Daniel James. |
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// Distributed under the Boost Software License, Version 1.0. (See accompanying |
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
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#if !defined(BOOST_FUNCTIONAL_HASH_DETAIL_FLOAT_FUNCTIONS_HPP) |
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#define BOOST_FUNCTIONAL_HASH_DETAIL_FLOAT_FUNCTIONS_HPP |
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#include <boost/config.hpp> |
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#include <boost/config/no_tr1/cmath.hpp> |
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#if defined(_MSC_VER) && (_MSC_VER >= 1020) |
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# pragma once |
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#endif |
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// The C++ standard requires that the C float functions are overloarded |
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// for float, double and long double in the std namespace, but some of the older |
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// library implementations don't support this. On some that don't, the C99 |
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// float functions (frexpf, frexpl, etc.) are available. |
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// |
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// The following tries to automatically detect which are available. |
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namespace boost { |
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namespace hash_detail { |
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// Returned by dummy versions of the float functions. |
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struct not_found { |
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// Implicitly convertible to float and long double in order to avoid |
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// a compile error when the dummy float functions are used. |
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inline operator float() const { return 0; } |
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inline operator long double() const { return 0; } |
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}; |
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// A type for detecting the return type of functions. |
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template <typename T> struct is; |
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template <> struct is<float> { char x[10]; }; |
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template <> struct is<double> { char x[20]; }; |
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template <> struct is<long double> { char x[30]; }; |
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template <> struct is<boost::hash_detail::not_found> { char x[40]; }; |
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// Used to convert the return type of a function to a type for sizeof. |
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template <typename T> is<T> float_type(T); |
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// call_ldexp |
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// |
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// This will get specialized for float and long double |
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template <typename Float> struct call_ldexp |
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{ |
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typedef double float_type; |
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inline double operator()(double a, int b) const |
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{ |
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using namespace std; |
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return ldexp(a, b); |
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} |
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}; |
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// call_frexp |
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// |
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// This will get specialized for float and long double |
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template <typename Float> struct call_frexp |
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{ |
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typedef double float_type; |
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inline double operator()(double a, int* b) const |
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{ |
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using namespace std; |
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return frexp(a, b); |
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} |
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}; |
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} |
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} |
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// A namespace for dummy functions to detect when the actual function we want |
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// isn't available. ldexpl, ldexpf etc. might be added tby the macros below. |
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// |
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// AFAICT these have to be outside of the boost namespace, as if they're in |
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// the boost namespace they'll always be preferable to any other function |
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// (since the arguments are built in types, ADL can't be used). |
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namespace boost_hash_detect_float_functions { |
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template <class Float> boost::hash_detail::not_found ldexp(Float, int); |
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template <class Float> boost::hash_detail::not_found frexp(Float, int*); |
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} |
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// Macros for generating specializations of call_ldexp and call_frexp. |
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// |
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// check_cpp and check_c99 check if the C++ or C99 functions are available. |
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// |
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// Then the call_* functions select an appropriate implementation. |
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// |
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// I used c99_func in a few places just to get a unique name. |
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// |
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// Important: when using 'using namespace' at namespace level, include as |
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// little as possible in that namespace, as Visual C++ has an odd bug which |
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// can cause the namespace to be imported at the global level. This seems to |
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// happen mainly when there's a template in the same namesapce. |
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#define BOOST_HASH_CALL_FLOAT_FUNC(cpp_func, c99_func, type1, type2) \ |
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namespace boost_hash_detect_float_functions { \ |
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template <class Float> \ |
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boost::hash_detail::not_found c99_func(Float, type2); \ |
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} \ |
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\ |
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namespace boost { \ |
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namespace hash_detail { \ |
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namespace c99_func##_detect { \ |
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using namespace std; \ |
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using namespace boost_hash_detect_float_functions; \ |
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\ |
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struct check { \ |
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static type1 x; \ |
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static type2 y; \ |
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BOOST_STATIC_CONSTANT(bool, cpp = \ |
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sizeof(float_type(cpp_func(x,y))) \ |
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== sizeof(is<type1>)); \ |
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BOOST_STATIC_CONSTANT(bool, c99 = \ |
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sizeof(float_type(c99_func(x,y))) \ |
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== sizeof(is<type1>)); \ |
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}; \ |
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} \ |
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\ |
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template <bool x> \ |
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struct call_c99_##c99_func : \ |
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boost::hash_detail::call_##cpp_func<double> {}; \ |
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\ |
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template <> \ |
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struct call_c99_##c99_func<true> { \ |
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typedef type1 float_type; \ |
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\ |
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template <typename T> \ |
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inline type1 operator()(type1 a, T b) const \ |
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{ \ |
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using namespace std; \ |
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return c99_func(a, b); \ |
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} \ |
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}; \ |
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\ |
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template <bool x> \ |
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struct call_cpp_##c99_func : \ |
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call_c99_##c99_func< \ |
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::boost::hash_detail::c99_func##_detect::check::c99 \ |
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> {}; \ |
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\ |
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template <> \ |
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struct call_cpp_##c99_func<true> { \ |
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typedef type1 float_type; \ |
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\ |
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template <typename T> \ |
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inline type1 operator()(type1 a, T b) const \ |
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{ \ |
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using namespace std; \ |
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return cpp_func(a, b); \ |
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} \ |
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}; \ |
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\ |
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template <> \ |
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struct call_##cpp_func<type1> : \ |
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call_cpp_##c99_func< \ |
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::boost::hash_detail::c99_func##_detect::check::cpp \ |
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> {}; \ |
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} \ |
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} |
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#define BOOST_HASH_CALL_FLOAT_MACRO(cpp_func, c99_func, type1, type2) \ |
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namespace boost { \ |
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namespace hash_detail { \ |
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\ |
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template <> \ |
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struct call_##cpp_func<type1> { \ |
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typedef type1 float_type; \ |
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inline type1 operator()(type1 x, type2 y) const { \ |
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return c99_func(x, y); \ |
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} \ |
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}; \ |
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} \ |
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} |
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#if defined(ldexpf) |
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BOOST_HASH_CALL_FLOAT_MACRO(ldexp, ldexpf, float, int) |
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#else |
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BOOST_HASH_CALL_FLOAT_FUNC(ldexp, ldexpf, float, int) |
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#endif |
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#if defined(ldexpl) |
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BOOST_HASH_CALL_FLOAT_MACRO(ldexp, ldexpl, long double, int) |
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#else |
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BOOST_HASH_CALL_FLOAT_FUNC(ldexp, ldexpl, long double, int) |
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#endif |
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#if defined(frexpf) |
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BOOST_HASH_CALL_FLOAT_MACRO(frexp, frexpf, float, int*) |
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#else |
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BOOST_HASH_CALL_FLOAT_FUNC(frexp, frexpf, float, int*) |
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#endif |
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#if defined(frexpl) |
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BOOST_HASH_CALL_FLOAT_MACRO(frexp, frexpl, long double, int*) |
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#else |
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BOOST_HASH_CALL_FLOAT_FUNC(frexp, frexpl, long double, int*) |
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#endif |
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#undef BOOST_HASH_CALL_FLOAT_MACRO |
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#undef BOOST_HASH_CALL_FLOAT_FUNC |
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namespace boost |
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{ |
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namespace hash_detail |
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{ |
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template <typename Float1, typename Float2> |
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struct select_hash_type_impl { |
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typedef double type; |
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}; |
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template <> |
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struct select_hash_type_impl<float, float> { |
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typedef float type; |
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}; |
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template <> |
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struct select_hash_type_impl<long double, long double> { |
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typedef long double type; |
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}; |
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// select_hash_type |
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// |
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// If there is support for a particular floating point type, use that |
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// otherwise use double (there's always support for double). |
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template <typename Float> |
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struct select_hash_type : select_hash_type_impl< |
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BOOST_DEDUCED_TYPENAME call_ldexp<Float>::float_type, |
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BOOST_DEDUCED_TYPENAME call_frexp<Float>::float_type |
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> {}; |
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} |
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} |
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#endif
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