Chris@16: //  declval.hpp  -------------------------------------------------------------//
Chris@16: 
Chris@16: //  Copyright 2010 Vicente J. Botet Escriba
Chris@16: 
Chris@16: //  Distributed under the Boost Software License, Version 1.0.
Chris@16: //  See http://www.boost.org/LICENSE_1_0.txt
Chris@16: 
Chris@16: #ifndef BOOST_UTILITY_DECLVAL_HPP
Chris@16: #define BOOST_UTILITY_DECLVAL_HPP
Chris@16: 
Chris@16: #include <boost/config.hpp>
Chris@16: 
Chris@16: //----------------------------------------------------------------------------//
Chris@16: 
Chris@16: #include <boost/type_traits/add_rvalue_reference.hpp>
Chris@16: 
Chris@16: //----------------------------------------------------------------------------//
Chris@16: //                                                                            //
Chris@16: //                           C++03 implementation of                          //
Chris@16: //                   20.2.4 Function template declval [declval]               //
Chris@16: //                          Written by Vicente J. Botet Escriba               //
Chris@16: //                                                                            //
Chris@16: // 1 The library provides the function template declval to simplify the
Chris@16: // definition of expressions which occur as unevaluated operands.
Chris@16: // 2 Remarks: If this function is used, the program is ill-formed.
Chris@16: // 3 Remarks: The template parameter T of declval may be an incomplete type.
Chris@16: // [ Example:
Chris@16: //
Chris@16: // template <class To, class From>
Chris@16: // decltype(static_cast<To>(declval<From>())) convert(From&&);
Chris@16: //
Chris@16: // declares a function template convert which only participates in overloading
Chris@16: // if the type From can be explicitly converted to type To. For another example
Chris@16: // see class template common_type (20.9.7.6). -end example ]
Chris@16: //----------------------------------------------------------------------------//
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16:     template <typename T>
Chris@16:     typename add_rvalue_reference<T>::type declval() BOOST_NOEXCEPT; // as unevaluated operand
Chris@16: 
Chris@16: }  // namespace boost
Chris@16: 
Chris@16: #endif  // BOOST_UTILITY_DECLVAL_HPP