63e88f80
 Hu Chunming
提交三方库
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// (C) Copyright 2007-2009 Andrew Sutton
//
// Use, modification and distribution are subject to the
// Boost Software License, Version 1.0 (See accompanying file
// LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_GRAPH_NUMERIC_VALUES_HPP
#define BOOST_GRAPH_NUMERIC_VALUES_HPP
#include <limits>
namespace boost
{
#define BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(type) \
template <> struct numeric_values< type > \
{ \
typedef type value_type; \
static type zero() { return 0.0; } \
static type infinity() \
{ \
return std::numeric_limits< type >::infinity(); \
} \
};
/**
* This generic type reports various numeric values for some type. In the
* general case, numeric values simply treat their maximum value as infinity
* and the default-constructed value as 0.
*
* Specializations of this template can redefine the notions of zero and
* infinity for various types. For example, the class is specialized for
* floating point types to use the built in notion of infinity.
*/
template < typename T > struct numeric_values
{
typedef T value_type;
static T zero() { return T(); }
static T infinity() { return (std::numeric_limits< T >::max)(); }
};
// Specializations for floating point types refer to 0.0 and their infinity
// value defined by numeric_limits.
BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(float)
BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(double)
BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(long double)
#undef BOOST_GRAPH_SPECIALIZE_NUMERIC_VALUE
}
#endif
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