boost/graph/numeric_values.hpp

   1 // (C) Copyright 2007-2009 Andrew Sutton
   2 //
   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 http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #ifndef BOOST_GRAPH_NUMERIC_VALUES_HPP
   8 #define BOOST_GRAPH_NUMERIC_VALUES_HPP
   9
  10 #include <limits>
  11
  12 namespace boost
  13 {
  14
  15 #define BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(type) \
  16     template <> struct numeric_values<type> { \
  17         typedef type value_type; \
  18         static type zero() { return 0.0; } \
  19         static type infinity() { return std::numeric_limits<type>::infinity(); } \
  20     };
  21
  22     /**
  23      * This generic type reports various numeric values for some type. In the
  24      * general case, numeric values simply treat their maximum value as infinity
  25      * and the default-constructed value as 0.
  26      *
  27      * Specializations of this template can redefine the notions of zero and
  28      * infinity for various types. For example, the class is specialized for
  29      * floating point types to use the built in notion of infinity.
  30      */
  31     template <typename T>
  32     struct numeric_values
  33     {
  34         typedef T value_type;
  35
  36         static T zero()
  37         { return T(); }
  38
  39         static T infinity()
  40         { return (std::numeric_limits<T>::max)(); }
  41     };
  42
  43     // Specializations for floating point types refer to 0.0 and their infinity
  44     // value defined by numeric_limits.
  45     BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(float)
  46     BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(double)
  47     BOOST_GRAPH_SPECIALIZE_NUMERIC_FLOAT(long double)
  48
  49 #undef BOOST_GRAPH_SPECIALIZE_NUMERIC_VALUE
  50 }
  51
  52 #endif