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- // declval.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_DECLVAL_HPP_INCLUDED
- #define BOOST_TYPE_TRAITS_DECLVAL_HPP_INCLUDED
- #include <boost/config.hpp>
- //----------------------------------------------------------------------------//
- #include <boost/type_traits/add_rvalue_reference.hpp>
- //----------------------------------------------------------------------------//
- // //
- // C++03 implementation of //
- // 20.2.4 Function template declval [declval] //
- // Written by Vicente J. Botet Escriba //
- // //
- // 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 participates in overloading
- // if the type From can be explicitly converted to type To. For another example
- // see class template common_type (20.9.7.6). -end example ]
- //----------------------------------------------------------------------------//
- namespace boost {
- template <typename T>
- typename add_rvalue_reference<T>::type declval() BOOST_NOEXCEPT; // as unevaluated operand
- } // namespace boost
- #endif // BOOST_TYPE_TRAITS_DECLVAL_HPP_INCLUDED
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