Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: /// \file arg.hpp
Chris@16: /// Contains definition of the argN transforms.
Chris@16: //
Chris@16: //  Copyright 2008 Eric Niebler. Distributed under the Boost
Chris@16: //  Software License, Version 1.0. (See accompanying file
Chris@16: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_PROTO_TRANSFORM_ARG_HPP_EAN_11_01_2007
Chris@16: #define BOOST_PROTO_TRANSFORM_ARG_HPP_EAN_11_01_2007
Chris@16: 
Chris@16: #include <boost/mpl/if.hpp>
Chris@16: #include <boost/proto/proto_fwd.hpp>
Chris@16: #include <boost/proto/traits.hpp>
Chris@16: #include <boost/proto/transform/impl.hpp>
Chris@16: #include <boost/type_traits/is_array.hpp>
Chris@16: #include <boost/proto/transform/env.hpp>
Chris@16: 
Chris@16: namespace boost { namespace proto
Chris@16: {
Chris@16: 
Chris@16:     /// \brief A PrimitiveTransform that returns the current expression
Chris@16:     /// unmodified
Chris@16:     ///
Chris@16:     /// Example:
Chris@16:     ///
Chris@16:     /// \code
Chris@16:     /// proto::terminal<int>::type i = {42};
Chris@16:     /// proto::terminal<int>::type & j = proto::_expr()(i);
Chris@16:     /// assert( boost::addressof(i) == boost::addressof(j) );
Chris@16:     /// \endcode
Chris@16:     struct _expr : transform<_expr>
Chris@16:     {
Chris@16:         template<typename Expr, typename State, typename Data>
Chris@16:         struct impl : transform_impl<Expr, State, Data>
Chris@16:         {
Chris@16:             typedef Expr result_type;
Chris@16: 
Chris@16:             /// Returns the current expression.
Chris@16:             /// \param e The current expression.
Chris@16:             /// \return \c e
Chris@16:             /// \throw nothrow
Chris@16:             BOOST_PROTO_RETURN_TYPE_STRICT_LOOSE(result_type, typename impl::expr_param)
Chris@16:             operator()(
Chris@16:                 typename impl::expr_param e
Chris@16:               , typename impl::state_param
Chris@16:               , typename impl::data_param
Chris@16:             ) const
Chris@16:             {
Chris@16:                 return e;
Chris@16:             }
Chris@16:         };
Chris@16:     };
Chris@16: 
Chris@16:     /// \brief A PrimitiveTransform that returns the current state
Chris@16:     /// unmodified
Chris@16:     ///
Chris@16:     /// Example:
Chris@16:     ///
Chris@16:     /// \code
Chris@16:     /// proto::terminal<int>::type i = {42};
Chris@16:     /// char ch = proto::_state()(i, 'a');
Chris@16:     /// assert( ch == 'a' );
Chris@16:     /// \endcode
Chris@16:     struct _state : transform<_state>
Chris@16:     {
Chris@16:         template<typename Expr, typename State, typename Data>
Chris@16:         struct impl : transform_impl<Expr, State, Data>
Chris@16:         {
Chris@16:             typedef State result_type;
Chris@16: 
Chris@16:             /// Returns the current state.
Chris@16:             /// \param s The current state.
Chris@16:             /// \return \c s
Chris@16:             /// \throw nothrow
Chris@16:             BOOST_PROTO_RETURN_TYPE_STRICT_LOOSE(result_type, typename impl::state_param)
Chris@16:             operator ()(
Chris@16:                 typename impl::expr_param
Chris@16:               , typename impl::state_param s
Chris@16:               , typename impl::data_param
Chris@16:             ) const
Chris@16:             {
Chris@16:                 return s;
Chris@16:             }
Chris@16:         };
Chris@16:     };
Chris@16: 
Chris@16:     /// \brief A PrimitiveTransform that returns the current data
Chris@16:     /// unmodified
Chris@16:     ///
Chris@16:     /// Example:
Chris@16:     ///
Chris@16:     /// \code
Chris@16:     /// proto::terminal<int>::type i = {42};
Chris@16:     /// std::string str("hello");
Chris@16:     /// std::string & data = proto::_data()(i, 'a', str);
Chris@16:     /// assert( &str == &data );
Chris@16:     /// \endcode
Chris@16:     struct _data : transform<_data>
Chris@16:     {
Chris@16:         template<typename Expr, typename State, typename Data>
Chris@16:         struct impl
Chris@16:           : mpl::if_c<
Chris@16:                 is_env<Data>::value
Chris@16:               , _env_var<data_type>
Chris@16:               , _env
Chris@16:             >::type::template impl<Expr, State, Data>
Chris@16:         {};
Chris@16:     };
Chris@16: 
Chris@16:     /// \brief A PrimitiveTransform that returns N-th child of the current
Chris@16:     /// expression.
Chris@16:     ///
Chris@16:     /// Example:
Chris@16:     ///
Chris@16:     /// \code
Chris@16:     /// proto::terminal<int>::type i = {42};
Chris@16:     /// proto::terminal<int>::type & j = proto::_child_c<0>()(-i);
Chris@16:     /// assert( boost::addressof(i) == boost::addressof(j) );
Chris@16:     /// \endcode
Chris@16:     template<int N>
Chris@16:     struct _child_c : transform<_child_c<N> >
Chris@16:     {
Chris@16:         template<typename Expr, typename State, typename Data>
Chris@16:         struct impl : transform_impl<Expr, State, Data>
Chris@16:         {
Chris@16:             typedef
Chris@16:                 typename result_of::child_c<Expr, N>::type
Chris@16:             result_type;
Chris@16: 
Chris@16:             /// Returns the N-th child of \c e
Chris@16:             /// \pre <tt>arity_of\<Expr\>::value \> N</tt> 
Chris@16:             /// \param e The current expression.
Chris@16:             /// \return <tt>proto::child_c\<N\>(e)</tt>
Chris@16:             /// \throw nothrow
Chris@16:             #ifdef BOOST_PROTO_STRICT_RESULT_OF
Chris@16:             result_type
Chris@16:             #else
Chris@16:             typename result_of::child_c<typename impl::expr_param, N>::type
Chris@16:             #endif
Chris@16:             operator ()(
Chris@16:                 typename impl::expr_param e
Chris@16:               , typename impl::state_param
Chris@16:               , typename impl::data_param
Chris@16:             ) const
Chris@16:             {
Chris@16:                 return proto::child_c<N>(e);
Chris@16:             }
Chris@16:         };
Chris@16:     };
Chris@16: 
Chris@16:     /// \brief A PrimitiveTransform that returns the value of the
Chris@16:     /// current terminal expression.
Chris@16:     ///
Chris@16:     /// Example:
Chris@16:     ///
Chris@16:     /// \code
Chris@16:     /// proto::terminal<int>::type i = {42};
Chris@16:     /// int j = proto::_value()(i);
Chris@16:     /// assert( 42 == j );
Chris@16:     /// \endcode
Chris@16:     struct _value : transform<_value>
Chris@16:     {
Chris@16:         template<typename Expr, typename State, typename Data>
Chris@16:         struct impl : transform_impl<Expr, State, Data>
Chris@16:         {
Chris@16:             typedef
Chris@16:                 typename result_of::value<Expr>::type
Chris@16:             result_type;
Chris@16: 
Chris@16:             /// Returns the value of the specified terminal expression.
Chris@16:             /// \pre <tt>arity_of\<Expr\>::value == 0</tt>.
Chris@16:             /// \param e The current expression.
Chris@16:             /// \return <tt>proto::value(e)</tt>
Chris@16:             /// \throw nothrow
Chris@16:             #ifdef BOOST_PROTO_STRICT_RESULT_OF
Chris@16:             typename mpl::if_c<is_array<result_type>::value, result_type &, result_type>::type
Chris@16:             #else
Chris@16:             typename result_of::value<typename impl::expr_param>::type
Chris@16:             #endif
Chris@16:             operator ()(
Chris@16:                 typename impl::expr_param e
Chris@16:               , typename impl::state_param
Chris@16:               , typename impl::data_param
Chris@16:             ) const
Chris@16:             {
Chris@16:                 return proto::value(e);
Chris@16:             }
Chris@16:         };
Chris@16:     };
Chris@16: 
Chris@16:     /// \brief A PrimitiveTransform that does nothing
Chris@16:     /// and returns void.
Chris@16:     struct _void : transform<_void>
Chris@16:     {
Chris@16:         template<typename Expr, typename State, typename Data>
Chris@16:         struct impl : transform_impl<Expr, State, Data>
Chris@16:         {
Chris@16:             typedef void result_type;
Chris@16: 
Chris@16:             /// Does nothing and returns void
Chris@16:             void operator ()(
Chris@16:                 typename impl::expr_param
Chris@16:               , typename impl::state_param
Chris@16:               , typename impl::data_param
Chris@16:             ) const
Chris@16:             {}
Chris@16:         };
Chris@16:     };
Chris@16: 
Chris@16:     /// \brief A unary CallableTransform that wraps its argument
Chris@16:     /// in a \c boost::reference_wrapper\<\>.
Chris@16:     ///
Chris@16:     /// Example:
Chris@16:     ///
Chris@16:     /// \code
Chris@16:     /// proto::terminal<int>::type i = {42};
Chris@16:     /// boost::reference_wrapper<proto::terminal<int>::type> j
Chris@16:     ///     = proto::when<_, proto::_byref(_)>()(i);
Chris@16:     /// assert( boost::addressof(i) == boost::addressof(j.get()) );
Chris@16:     /// \endcode
Chris@16:     struct _byref : callable
Chris@16:     {
Chris@16:         template<typename Sig>
Chris@16:         struct result;
Chris@16: 
Chris@16:         template<typename This, typename T>
Chris@16:         struct result<This(T)>
Chris@16:         {
Chris@16:             typedef boost::reference_wrapper<T const> const type;
Chris@16:         };
Chris@16: 
Chris@16:         template<typename This, typename T>
Chris@16:         struct result<This(T &)>
Chris@16:         {
Chris@16:             typedef boost::reference_wrapper<T> const type;
Chris@16:         };
Chris@16: 
Chris@16:         /// Wrap the parameter \c t in a \c boost::reference_wrapper\<\>
Chris@16:         /// \param t The object to wrap
Chris@16:         /// \return <tt>boost::ref(t)</tt>
Chris@16:         /// \throw nothrow
Chris@16:         template<typename T>
Chris@16:         boost::reference_wrapper<T> const operator ()(T &t) const
Chris@16:         {
Chris@16:             return boost::reference_wrapper<T>(t);
Chris@16:         }
Chris@16: 
Chris@16:         /// \overload
Chris@16:         ///
Chris@16:         template<typename T>
Chris@16:         boost::reference_wrapper<T const> const operator ()(T const &t) const
Chris@16:         {
Chris@16:             return boost::reference_wrapper<T const>(t);
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     /// \brief A unary CallableTransform that strips references
Chris@16:     /// and \c boost::reference_wrapper\<\> from its argument.
Chris@16:     ///
Chris@16:     /// Example:
Chris@16:     ///
Chris@16:     /// \code
Chris@16:     /// proto::terminal<int>::type i = {42};
Chris@16:     /// int j = 67;
Chris@16:     /// int k = proto::when<_, proto::_byval(proto::_state)>()(i, boost::ref(j));
Chris@16:     /// assert( 67 == k );
Chris@16:     /// \endcode
Chris@16:     struct _byval : callable
Chris@16:     {
Chris@16:         template<typename Sig>
Chris@16:         struct result;
Chris@16: 
Chris@16:         template<typename This, typename T>
Chris@16:         struct result<This(T)>
Chris@16:         {
Chris@16:             typedef T type;
Chris@16:         };
Chris@16: 
Chris@16:         template<typename This, typename T>
Chris@16:         struct result<This(T &)>
Chris@16:           : result<This(T)>
Chris@16:         {};
Chris@16: 
Chris@16:         template<typename This, typename T>
Chris@16:         struct result<This(boost::reference_wrapper<T>)>
Chris@16:           : result<This(T)>
Chris@16:         {};
Chris@16: 
Chris@16:         /// \param t The object to unref
Chris@16:         /// \return <tt>t</tt>
Chris@16:         /// \throw nothrow
Chris@16:         template<typename T>
Chris@16:         T operator ()(T const &t) const
Chris@16:         {
Chris@16:             return t;
Chris@16:         }
Chris@16: 
Chris@16:         /// \overload
Chris@16:         ///
Chris@16:         template<typename T>
Chris@16:         T operator ()(boost::reference_wrapper<T> const &t) const
Chris@16:         {
Chris@16:             return t;
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     /// INTERNAL ONLY
Chris@16:     ///
Chris@16:     template<>
Chris@16:     struct is_callable<_expr>
Chris@16:       : mpl::true_
Chris@16:     {};
Chris@16: 
Chris@16:     /// INTERNAL ONLY
Chris@16:     ///
Chris@16:     template<>
Chris@16:     struct is_callable<_state>
Chris@16:       : mpl::true_
Chris@16:     {};
Chris@16: 
Chris@16:     /// INTERNAL ONLY
Chris@16:     ///
Chris@16:     template<>
Chris@16:     struct is_callable<_data>
Chris@16:       : mpl::true_
Chris@16:     {};
Chris@16: 
Chris@16:     /// INTERNAL ONLY
Chris@16:     ///
Chris@16:     template<int N>
Chris@16:     struct is_callable<_child_c<N> >
Chris@16:       : mpl::true_
Chris@16:     {};
Chris@16: 
Chris@16:     /// INTERNAL ONLY
Chris@16:     ///
Chris@16:     template<>
Chris@16:     struct is_callable<_value>
Chris@16:       : mpl::true_
Chris@16:     {};
Chris@16: 
Chris@16:     /// INTERNAL ONLY
Chris@16:     ///
Chris@16:     template<>
Chris@16:     struct is_callable<_byref>
Chris@16:       : mpl::true_
Chris@16:     {};
Chris@16: 
Chris@16:     /// INTERNAL ONLY
Chris@16:     ///
Chris@16:     template<>
Chris@16:     struct is_callable<_byval>
Chris@16:       : mpl::true_
Chris@16:     {};
Chris@16: 
Chris@16: }}
Chris@16: 
Chris@16: #endif