ceph/src/boost/boost/type_traits/declval.hpp

   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