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is_value.hpp
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/*============================================================================== Copyright (c) 2005-2010 Joel de Guzman Copyright (c) 2015 John Fletcher Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ==============================================================================*/ #ifndef BOOST_PHOENIX_CORE_IS_VALUE_HPP #define BOOST_PHOENIX_CORE_IS_VALUE_HPP #include <boost/mpl/bool.hpp> // Copied from is_actor.hpp // Note to Thomas and any future maintainer: please make this as // lightweight as possible (as it is right now). namespace boost { namespace phoenix { /////////////////////////////////////////////////////////////////////////////// // // is_value<T> // // Tests if T is a value. Evaluates to mpl::true_ or mpl::false_ // /////////////////////////////////////////////////////////////////////////////// namespace expression { template <typename T> struct value; } template <typename T, typename Enable = void> struct is_value : mpl::false_ {}; template <typename T> struct is_value<T const> : is_value<T> {}; template <typename T> struct is_value<T &> : is_value<T> {}; // This does not seem to work. // There is an alternative in value.hpp which does work. template <typename T> struct is_value< expression::value<T> > : mpl::true_ {}; template <typename T> bool is_val(T const & /* t */) { return is_value<T>::value; } }} #endif