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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 
compose_property_map(const FPMap & f_p,const GPMap & g_p)32     inline compose_property_map(const FPMap &f_p, const GPMap &g_p):
33         f(f_p), g(g_p)
34     {}
35 
compose_property_map()36     inline compose_property_map() {}
37 
38     inline reference
operator [](const key_type & v) const39     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
get(const compose_property_map & m,const key_type & k)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
put(const compose_property_map & m,const key_type & k,const value_type & v)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>
make_compose_property_map(const FPMap & f,const GPMap & g)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
82