text: //  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
  