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- /*=============================================================================
- Copyright (c) 2001-2011 Joel de Guzman
- 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)
- ==============================================================================*/
- #if !defined(BOOST_SPIRIT_EXPAND_ARG_FEB_19_2007_1107AM)
- #define BOOST_SPIRIT_EXPAND_ARG_FEB_19_2007_1107AM
- #if defined(_MSC_VER)
- #pragma once
- #endif
- #include <boost/mpl/bool.hpp>
- #include <boost/mpl/or.hpp>
- #include <boost/mpl/identity.hpp>
- #include <boost/mpl/eval_if.hpp>
- #include <boost/utility/result_of.hpp>
- #include <boost/type_traits/is_scalar.hpp>
- #include <boost/spirit/home/support/string_traits.hpp>
- namespace boost { namespace spirit { namespace detail
- {
- ///////////////////////////////////////////////////////////////////////////
- template <typename Context>
- struct expand_arg
- {
- template <typename T>
- struct result_type
- {
- // This is a temporary hack. The better way is to detect if T
- // can be called given unused context.
- typedef typename
- mpl::eval_if<
- mpl::or_<is_scalar<T>, traits::is_string<T> >
- , mpl::identity<T const &>
- , boost::result_of<T(unused_type, Context)>
- >::type
- type;
- };
- template <typename T>
- struct result;
- template <typename F, typename A0>
- struct result<F(A0)>
- : result_type<A0> {};
- template <typename F, typename A0>
- struct result<F(A0&)>
- : result_type<A0> {};
- expand_arg(Context& context_)
- : context(context_)
- {
- }
- template <typename T>
- typename result_type<T>::type
- call(T const& f, mpl::false_) const
- {
- return f(unused, context);
- }
- template <typename T>
- typename result_type<T>::type
- call(T const& val, mpl::true_) const
- {
- return val;
- }
- template <typename T>
- typename result_type<T>::type
- operator()(T const& x) const
- {
- return call(x, mpl::or_<is_scalar<T>, traits::is_string<T> >());
- }
- Context& context;
- // silence MSVC warning C4512: assignment operator could not be generated
- BOOST_DELETED_FUNCTION(expand_arg& operator= (expand_arg const&))
- };
- }}}
- #endif
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