boost/fusion/support/deduce.hpp
/*=============================================================================
Copyright (c) 2007 Tobias Schwinger
Use modification and distribution are subject to 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).
==============================================================================*/
#if !defined(BOOST_FUSION_SUPPORT_DEDUCE_HPP_INCLUDED)
#define BOOST_FUSION_SUPPORT_DEDUCE_HPP_INCLUDED
#include <boost/fusion/support/config.hpp>
#include <boost/core/ref.hpp>
#ifndef BOOST_NO_CXX11_HDR_FUNCTIONAL
#include <functional>
#endif
namespace boost { namespace fusion { namespace traits
{
template <typename T> struct deduce;
//----- ---- --- -- - - - -
// Non-references pass unchanged
template <typename T>
struct deduce
{
typedef T type;
};
template <typename T>
struct deduce<T const>
{
typedef T type;
};
template <typename T>
struct deduce<T volatile>
{
typedef T type;
};
template <typename T>
struct deduce<T const volatile>
{
typedef T type;
};
// Keep references on mutable LValues
template <typename T>
struct deduce<T &>
{
typedef T & type;
};
template <typename T>
struct deduce<T volatile&>
{
typedef T volatile& type;
};
// Store away potential RValues
template <typename T>
struct deduce<T const&>
{
typedef T type;
};
template <typename T>
struct deduce<T const volatile&>
{
typedef T type;
};
// Unwrap Boost.RefS (referencee cv is deduced)
template <typename T>
struct deduce<reference_wrapper<T> & >
{
typedef T& type;
};
template <typename T>
struct deduce<reference_wrapper<T> const & >
{
typedef T& type;
};
// Also unwrap C++11 std::ref if available (referencee cv is deduced)
#ifndef BOOST_NO_CXX11_HDR_FUNCTIONAL
template <typename T>
struct deduce<std::reference_wrapper<T> &>
{
typedef T& type;
};
template <typename T>
struct deduce<std::reference_wrapper<T> const &>
{
typedef T& type;
};
#endif
// Keep references on arrays, even if const
template <typename T, int N>
struct deduce<T(&)[N]>
{
typedef T(&type)[N];
};
template <typename T, int N>
struct deduce<volatile T(&)[N]>
{
typedef volatile T(&type)[N];
};
template <typename T, int N>
struct deduce<const T(&)[N]>
{
typedef const T(&type)[N];
};
template <typename T, int N>
struct deduce<const volatile T(&)[N]>
{
typedef const volatile T(&type)[N];
};
}}}
#endif
