deps/boost_1_63_0/boost/property_map/compose_property_map.hpp

   1 // Copyright (C) 2013 Eurodecision
   2 // Authors: Guillaume Pinot
   3 //
   4 // Distributed under the Boost Software License, Version 1.0. (See
   5 // accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt)
   7 //
   8 // See http://www.boost.org/libs/property_map for documentation.
   9
  10 #ifndef BOOST_PROPERTY_MAP_COMPOSE_PROPERTY_MAP_HPP
  11 #define BOOST_PROPERTY_MAP_COMPOSE_PROPERTY_MAP_HPP
  12
  13 #include <boost/property_map/property_map.hpp>
  14 #include <boost/type_traits.hpp>
  15
  16 namespace boost {
  17
  18 // A compose property map: make_compose_property_map(f, g)[x] == f[g[x]]
  19 //
  20 // g must be a readable property map.
  21 // The category of compose_property_map(f, g) is the category of f.
  22
  23 template <typename FPMap, typename GPMap>
  24 class compose_property_map
  25 {
  26 public:
  27     typedef typename boost::property_traits<FPMap>::category category;
  28     typedef typename boost::property_traits<GPMap>::key_type key_type;
  29     typedef typename boost::property_traits<FPMap>::value_type value_type;
  30     typedef typename boost::property_traits<FPMap>::reference reference;
  31
  32     inline compose_property_map(const FPMap &f_p, const GPMap &g_p):
  33         f(f_p), g(g_p)
  34     {}
  35
  36     inline compose_property_map() {}
  37
  38     inline reference
  39     operator[](const key_type &v) const {
  40         return f[get(g, v)];
  41     }
  42
  43     // return type of get():
  44     // if (reference is not a ref)
  45     //     value_type
  46     // else if (reference is const)
  47     //     reference
  48     // else
  49     //     const value_type&
  50     inline friend typename boost::mpl::if_<
  51         boost::mpl::not_< boost::is_reference<reference> >,
  52         value_type,
  53         typename boost::mpl::if_<
  54             boost::is_const<reference>,
  55             reference,
  56             const value_type&
  57             >::type
  58         >::type
  59     get(const compose_property_map &m, const key_type &k) {
  60         return get(m.f, get(m.g, k));
  61     }
  62
  63     inline friend void
  64     put(const compose_property_map &m, const key_type &k, const value_type &v) {
  65         put(m.f, get(m.g, k), v);
  66     }
  67
  68 private:
  69     FPMap f;
  70     GPMap g;
  71 };
  72
  73 template <class FPMap, class GPMap>
  74 inline compose_property_map<FPMap, GPMap>
  75 make_compose_property_map(const FPMap &f, const GPMap &g) {
  76     return compose_property_map<FPMap, GPMap>(f, g);
  77 }
  78
  79 } // namespace boost
  80
  81 #endif // BOOST_PROPERTY_MAP_COMPOSE_PROPERTY_MAP_HPP