/Src/Dependencies/Boost/boost/spirit/home/phoenix/scope/let.hpp

  1/*=============================================================================
  2    Copyright (c) 2001-2007 Joel de Guzman
  3    Copyright (c) 2004 Daniel Wallin
  4
  5    Distributed under the Boost Software License, Version 1.0. (See accompanying 
  6    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  7==============================================================================*/
  8#ifndef PHOENIX_SCOPE_LET_HPP
  9#define PHOENIX_SCOPE_LET_HPP
 10
 11#include <boost/spirit/home/phoenix/core/limits.hpp>
 12#include <boost/spirit/home/phoenix/core/composite.hpp>
 13#include <boost/spirit/home/phoenix/scope/scoped_environment.hpp>
 14#include <boost/spirit/home/phoenix/scope/detail/local_variable.hpp>
 15#include <boost/spirit/home/phoenix/detail/local_reference.hpp>
 16#include <boost/spirit/home/phoenix/core/actor.hpp>
 17#include <boost/fusion/include/transform.hpp>
 18#include <boost/fusion/include/as_vector.hpp>
 19#include <boost/mpl/eval_if.hpp>
 20#include <boost/mpl/bool.hpp>
 21
 22namespace boost { namespace phoenix
 23{
 24    template <typename Base, typename Vars, typename Map>
 25    struct let_actor : Base
 26    {
 27        typedef typename
 28            mpl::fold<
 29                Vars
 30              , mpl::false_
 31              , detail::compute_no_nullary
 32            >::type
 33        no_nullary;
 34        
 35        template <typename Env>
 36        struct result
 37        {
 38            typedef typename 
 39                fusion::result_of::as_vector<
 40                    typename fusion::result_of::transform<
 41                        Vars
 42                      , detail::initialize_local<Env>
 43                    >::type
 44                >::type 
 45            locals_type;
 46
 47            typedef typename Base::template
 48                result<scoped_environment<Env, Env, locals_type, Map> >::type
 49            result_type;
 50            
 51            typedef typename 
 52                detail::unwrap_local_reference<result_type>::type 
 53            type;
 54        };
 55
 56        let_actor(Base const& base, Vars const& vars)
 57            : Base(base), vars(vars) {}
 58
 59        template <typename Env>
 60        typename result<Env>::type
 61        eval(Env const& env) const
 62        {
 63            typedef typename 
 64                fusion::result_of::as_vector<
 65                    typename fusion::result_of::transform<
 66                        Vars
 67                      , detail::initialize_local<Env>
 68                    >::type
 69                >::type 
 70            locals_type;
 71
 72            locals_type locals = 
 73                fusion::as_vector(
 74                    fusion::transform(
 75                        vars
 76                      , detail::initialize_local<Env>(env)));
 77            
 78            typedef typename result<Env>::type RT;
 79            return RT(Base::eval(
 80                scoped_environment<Env, Env, locals_type, Map>(
 81                    env
 82                  , env
 83                  , locals)));
 84        }
 85
 86        Vars vars;
 87    };
 88    
 89    template <typename Vars, typename Map>
 90    struct let_actor_gen
 91    {
 92        template <typename Base>
 93        actor<let_actor<Base, Vars, Map> > const
 94        operator[](actor<Base> const& base) const
 95        {
 96            return let_actor<Base, Vars, Map>(base, vars);
 97        }
 98
 99        let_actor_gen(Vars const& vars)
100            : vars(vars) {}
101
102        Vars vars;
103    };
104
105    template <typename Key>
106    struct local_variable; // forward
107    struct assign_eval; // forward
108
109    struct let_gen
110    {
111        template <typename K0, typename V0>
112        let_actor_gen<
113            fusion::vector<V0>
114          , detail::map_local_index_to_tuple<K0>
115        >
116        operator()(
117            actor<composite<assign_eval, fusion::vector<local_variable<K0>, V0> > > const& a0
118        ) const
119        {
120            return fusion::vector<V0>(fusion::at_c<1>(a0));
121        }
122    
123        template <typename K0, typename K1, typename V0, typename V1>
124        let_actor_gen<
125            fusion::vector<V0, V1>
126          , detail::map_local_index_to_tuple<K0, K1>
127        >
128        operator()(
129            actor<composite<assign_eval, fusion::vector<local_variable<K0>, V0> > > const& a0
130          , actor<composite<assign_eval, fusion::vector<local_variable<K1>, V1> > > const& a1
131        ) const
132        {
133            return fusion::vector<V0, V1>(fusion::at_c<1>(a0), fusion::at_c<1>(a1));
134        }
135        
136        // Bring in the rest...
137        #define PHOENIX_LOCAL_GEN_NAME let_actor_gen
138        #include <boost/spirit/home/phoenix/scope/detail/local_gen.hpp>
139        #undef PHOENIX_LOCAL_GEN_NAME
140    };
141
142    let_gen const let = let_gen();
143}}
144
145#endif