Chris@16: /*==============================================================================
Chris@16:     Copyright (c) 2001-2010 Joel de Guzman
Chris@16:     Copyright (c) 2010 Eric Niebler
Chris@16: 
Chris@16:     Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@16:     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: ==============================================================================*/
Chris@16: #ifndef BOOST_PHOENIX_STATEMENT_IF_HPP
Chris@16: #define BOOST_PHOENIX_STATEMENT_IF_HPP
Chris@16: 
Chris@101: #include <boost/phoenix/config.hpp>
Chris@16: #include <boost/phoenix/core/limits.hpp>
Chris@16: #include <boost/phoenix/core/actor.hpp>
Chris@16: #include <boost/phoenix/core/call.hpp>
Chris@16: #include <boost/phoenix/core/expression.hpp>
Chris@16: #include <boost/phoenix/core/meta_grammar.hpp>
Chris@16: #include <boost/phoenix/core/is_actor.hpp>
Chris@16: 
Chris@16: #ifdef BOOST_MSVC
Chris@16: #pragma warning(push)
Chris@16: #pragma warning(disable: 4355) // 'this' used in base member initializer list
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost { namespace phoenix
Chris@16: {
Chris@16:     template <typename> struct if_actor;
Chris@16: }}
Chris@16:     
Chris@16: BOOST_PHOENIX_DEFINE_EXPRESSION_EXT(
Chris@16:     if_actor
Chris@16:   , (boost)(phoenix)(if_)
Chris@16:   , (meta_grammar) // Cond
Chris@16:     (meta_grammar) // Then
Chris@16: )
Chris@16:     
Chris@16: BOOST_PHOENIX_DEFINE_EXPRESSION(
Chris@16:     (boost)(phoenix)(if_else_statement)
Chris@16:   , (meta_grammar) // Cond
Chris@16:     (meta_grammar) // Then
Chris@16:     (meta_grammar) // Else
Chris@16: )
Chris@16: 
Chris@16: namespace boost { namespace phoenix
Chris@16: {
Chris@16:     ////////////////////////////////////////////////////////////////////////////
Chris@16:     // If-Else statements
Chris@16:     ////////////////////////////////////////////////////////////////////////////
Chris@16:     
Chris@16:     // Function for evaluating lambdas like:
Chris@16:     // if_( foo )[ bar ]
Chris@16:     // and
Chris@16:     // if_( foo )[ bar ].else_[ baz ]
Chris@16:     struct if_else_eval
Chris@16:     {
Chris@16:         typedef void result_type;
Chris@16:         
Chris@16:         template<typename Cond, typename Then, typename Context>
Chris@16:         result_type
Chris@16:         operator()(Cond const & cond, Then const & then, Context const & ctx) const
Chris@16:         {
Chris@16:             if(boost::phoenix::eval(cond, ctx))
Chris@16:                 boost::phoenix::eval(then, ctx);
Chris@16:         }
Chris@16:         
Chris@16:         template<typename Cond, typename Then, typename Else, typename Context>
Chris@16:         result_type
Chris@16:         operator()(
Chris@16:               Cond const & cond
Chris@16:             , Then const & then
Chris@16:             , Else const & else_
Chris@16:             , Context const & ctx
Chris@16:         ) const
Chris@16:         {
Chris@16:             if(boost::phoenix::eval(cond, ctx))
Chris@16:                 boost::phoenix::eval(then, ctx);
Chris@16:             else
Chris@16:                 boost::phoenix::eval(else_, ctx);
Chris@16:         }
Chris@16:     };
Chris@16:     
Chris@16:     template <typename Dummy>
Chris@16:     struct default_actions::when<rule::if_, Dummy>
Chris@16:         : call<if_else_eval, Dummy>
Chris@16:     {};
Chris@16:     
Chris@16:     template <typename Dummy>
Chris@16:     struct default_actions::when<rule::if_else_statement, Dummy>
Chris@16:         : call<if_else_eval, Dummy>
Chris@16:     {};
Chris@16: 
Chris@16: 
Chris@16:     // Generator for .else_[ expr ] branch.
Chris@16:     template<typename Cond, typename Then>
Chris@16:     struct else_gen
Chris@16:     {
Chris@101:         else_gen(Cond const & cond_, Then const & then_)
Chris@101:             : cond(cond_)
Chris@101:             , then(then_) {}
Chris@16: 
Chris@16:         template<typename Else>
Chris@16:         typename expression::if_else_statement<Cond, Then, Else>::type const
Chris@16:         operator[](Else const & else_) const
Chris@16:         {
Chris@16:             return expression::if_else_statement<Cond, Then, Else>::make(cond, then, else_);
Chris@16:         }
Chris@16: 
Chris@16:         Cond cond;
Chris@16:         Then then;
Chris@16:     };
Chris@16: 
Chris@16:     // We subclass actor so we can provide the member else_ (which is an
Chris@16:     // else_gen responsible for the .else_[ expr ] branch).
Chris@16:     template<typename Expr>
Chris@16:     struct if_actor : actor<Expr>
Chris@16:     {
Chris@16:         typedef actor<Expr> base_type;
Chris@16: 
Chris@16:         if_actor(base_type const & base)
Chris@16:             : base_type(base)
Chris@16:             , else_(proto::child_c<0>(*this), proto::child_c<1>(*this))
Chris@16:         {}
Chris@16: 
Chris@16:         typedef typename proto::result_of::child_c<Expr, 0>::type cond_type;
Chris@16:         typedef typename proto::result_of::child_c<Expr, 1>::type then_type;
Chris@16: 
Chris@16:         else_gen<cond_type, then_type> else_;
Chris@16:     };
Chris@16: 
Chris@16:     template <typename Expr>
Chris@16:     struct is_actor<if_actor<Expr> >
Chris@16:         : mpl::true_
Chris@16:     {};
Chris@16: 
Chris@16:     // Generator for if( cond )[ then ] branch.
Chris@16:     template<typename Cond>
Chris@16:     struct if_gen
Chris@16:     {
Chris@101:         if_gen(Cond const & cond_)
Chris@101:             : cond(cond_) {}
Chris@16: 
Chris@16:         template<typename Then>
Chris@16:         typename expression::if_<Cond, Then>::type const
Chris@16:         operator[](Then const & then) const
Chris@16:         {
Chris@16:             return expression::if_<Cond, Then>::make(cond, then);
Chris@16:         }
Chris@16: 
Chris@16:         Cond cond;
Chris@16:     };
Chris@16: 
Chris@16:     template<typename Cond>
Chris@16:     inline
Chris@16:     if_gen<Cond> const
Chris@16:     if_(Cond const & cond)
Chris@16:     {
Chris@16:         return if_gen<Cond>(cond);
Chris@16:     }
Chris@16:  
Chris@16: }}
Chris@16: 
Chris@16: #ifdef BOOST_MSVC
Chris@16: #pragma warning(pop)
Chris@16: #endif
Chris@16: 
Chris@16: #endif