boost/property_map/compose_property_map.hpp
// Copyright (C) 2013 Eurodecision
// Authors: Guillaume Pinot
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/property_map for documentation.
#ifndef BOOST_PROPERTY_MAP_COMPOSE_PROPERTY_MAP_HPP
#define BOOST_PROPERTY_MAP_COMPOSE_PROPERTY_MAP_HPP
#include <boost/property_map/property_map.hpp>
#include <boost/type_traits.hpp>
namespace boost {
// A compose property map: make_compose_property_map(f, g)[x] == f[g[x]]
//
// g must be a readable property map.
// The category of compose_property_map(f, g) is the category of f.
template <typename FPMap, typename GPMap>
class compose_property_map
{
public:
typedef typename boost::property_traits<FPMap>::category category;
typedef typename boost::property_traits<GPMap>::key_type key_type;
typedef typename boost::property_traits<FPMap>::value_type value_type;
typedef typename boost::property_traits<FPMap>::reference reference;
inline compose_property_map(const FPMap &f_p, const GPMap &g_p):
f(f_p), g(g_p)
{}
inline compose_property_map() {}
inline reference
operator[](const key_type &v) const {
return f[get(g, v)];
}
// return type of get():
// if (reference is not a ref)
// value_type
// else if (reference is const)
// reference
// else
// const value_type&
inline friend typename boost::mpl::if_<
boost::mpl::not_< boost::is_reference<reference> >,
value_type,
typename boost::mpl::if_<
boost::is_const<reference>,
reference,
const value_type&
>::type
>::type
get(const compose_property_map &m, const key_type &k) {
return get(m.f, get(m.g, k));
}
inline friend void
put(const compose_property_map &m, const key_type &k, const value_type &v) {
put(m.f, get(m.g, k), v);
}
private:
FPMap f;
GPMap g;
};
template <class FPMap, class GPMap>
inline compose_property_map<FPMap, GPMap>
make_compose_property_map(const FPMap &f, const GPMap &g) {
return compose_property_map<FPMap, GPMap>(f, g);
}
} // namespace boost
#endif // BOOST_PROPERTY_MAP_COMPOSE_PROPERTY_MAP_HPP