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// file : butl/multi-index -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
// license : MIT; see accompanying LICENSE file
#ifndef BUTL_MULTI_INDEX
#define BUTL_MULTI_INDEX
#include <utility> // declval()
#include <functional> // hash
namespace butl
{
// Google the "Emulating Boost.MultiIndex with Standard Containers" blog
// post for details.
//
template <typename T>
struct map_key
{
mutable const T* p;
map_key (const T* v = 0): p (v) {}
bool operator< (const map_key& x) const {return *p < *x.p;}
bool operator== (const map_key& x) const {return *p == *x.p;}
};
template <typename I>
struct map_iterator_adapter: I
{
typedef const typename I::value_type::second_type value_type;
typedef value_type* pointer;
typedef value_type& reference;
map_iterator_adapter () {}
map_iterator_adapter (I i): I (i) {}
map_iterator_adapter&
operator= (I i) {static_cast<I&> (*this) = i; return *this;}
reference operator* () const {return I::operator* ().second;}
pointer operator-> () const {return &I::operator-> ()->second;}
};
}
namespace std
{
template <typename T>
struct hash<butl::map_key<T>>: hash<T>
{
size_t
operator() (butl::map_key<T> x) const
noexcept (noexcept (declval<hash<T>> () (*x.p)))
{
return hash<T>::operator() (*x.p);
}
};
}
#endif // BUTL_MULTI_INDEX
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