50 lines
2.0 KiB
C++
50 lines
2.0 KiB
C++
// common_type.hpp ---------------------------------------------------------//
|
|
|
|
// Copyright 2010 Vicente J. Botet Escriba
|
|
|
|
// Distributed under the Boost Software License, Version 1.0.
|
|
// See http://www.boost.org/LICENSE_1_0.txt
|
|
|
|
#ifndef BOOST_TYPE_TRAITS_EXT_DECLVAL__HPP
|
|
#define BOOST_TYPE_TRAITS_EXT_DECLVAL__HPP
|
|
|
|
#include <boost/config.hpp>
|
|
|
|
//----------------------------------------------------------------------------//
|
|
|
|
#include <boost/type_traits/add_rvalue_reference.hpp>
|
|
//#include <boost/type_traits/add_lvalue_reference.hpp>
|
|
|
|
//----------------------------------------------------------------------------//
|
|
// //
|
|
// C++03 implementation of //
|
|
// Written by Vicente J. Botet Escriba //
|
|
//~ 20.3.4 Function template declval [declval]
|
|
//~ 1 The library provides the function template declval to simplify the definition of expressions which occur as
|
|
//~ unevaluated operands.
|
|
//~ 2 Remarks: If this function is used, the program is ill-formed.
|
|
//~ 3 Remarks: The template parameter T of declval may be an incomplete type.
|
|
//~ [ Example:
|
|
|
|
//~ template <class To, class From>
|
|
//~ decltype(static_cast<To>(declval<From>())) convert(From&&);
|
|
|
|
//~ declares a function template convert which only participats in overloading if the type From can be
|
|
//~ explicitly converted to type To. For another example see class template common_type (20.7.6.6). —end
|
|
//~ example ]
|
|
// //
|
|
//----------------------------------------------------------------------------//
|
|
|
|
namespace boost {
|
|
|
|
//#if !defined(BOOST_NO_RVALUE_REFERENCES)
|
|
template <typename T>
|
|
typename add_rvalue_reference<T>::type declval() BOOST_NOEXCEPT; // as unevaluated operand
|
|
//#else
|
|
// template <typename T>
|
|
// typename add_lvalue_reference<T>::type declval() BOOST_NOEXCEPT; // as unevaluated operand
|
|
//#endif
|
|
} // namespace boost
|
|
|
|
#endif // BOOST_TYPE_TRAITS_EXT_DECLVAL__HPP
|