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1 | // declval.hpp -------------------------------------------------------------// |
2 | ||
3 | // Copyright 2010 Vicente J. Botet Escriba | |
4 | ||
5 | // Distributed under the Boost Software License, Version 1.0. | |
6 | // See http://www.boost.org/LICENSE_1_0.txt | |
7 | ||
8 | #ifndef BOOST_TYPE_TRAITS_DECLVAL_HPP_INCLUDED | |
9 | #define BOOST_TYPE_TRAITS_DECLVAL_HPP_INCLUDED | |
10 | ||
11 | #include <boost/config.hpp> | |
12 | ||
13 | //----------------------------------------------------------------------------// | |
14 | ||
15 | #include <boost/type_traits/add_rvalue_reference.hpp> | |
16 | ||
17 | //----------------------------------------------------------------------------// | |
18 | // // | |
19 | // C++03 implementation of // | |
20 | // 20.2.4 Function template declval [declval] // | |
21 | // Written by Vicente J. Botet Escriba // | |
22 | // // | |
23 | // 1 The library provides the function template declval to simplify the | |
24 | // definition of expressions which occur as unevaluated operands. | |
25 | // 2 Remarks: If this function is used, the program is ill-formed. | |
26 | // 3 Remarks: The template parameter T of declval may be an incomplete type. | |
27 | // [ Example: | |
28 | // | |
29 | // template <class To, class From> | |
30 | // decltype(static_cast<To>(declval<From>())) convert(From&&); | |
31 | // | |
32 | // declares a function template convert which only participates in overloading | |
33 | // if the type From can be explicitly converted to type To. For another example | |
34 | // see class template common_type (20.9.7.6). -end example ] | |
35 | //----------------------------------------------------------------------------// | |
36 | ||
37 | namespace boost { | |
38 | ||
39 | template <typename T> | |
40 | typename add_rvalue_reference<T>::type declval() BOOST_NOEXCEPT; // as unevaluated operand | |
41 | ||
42 | } // namespace boost | |
43 | ||
44 | #endif // BOOST_TYPE_TRAITS_DECLVAL_HPP_INCLUDED |