text: /*=============================================================================
      Copyright (c) 2001-2011 Joel de Guzman
      Copyright (c) 2001-2011 Hartmut Kaiser
  
      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(SPIRIT_PASS_CONTAINER_JANUARY_06_2009_0802PM)
  #define SPIRIT_PASS_CONTAINER_JANUARY_06_2009_0802PM
  
  #if defined(_MSC_VER)
  #pragma once
  #endif
  
  #include <boost/spirit/home/qi/detail/attributes.hpp>
  #include <boost/spirit/home/support/container.hpp>
  #include <boost/spirit/home/support/handles_container.hpp>
  #include <boost/type_traits/is_base_of.hpp>
  #include <boost/type_traits/is_convertible.hpp>
  #include <boost/mpl/bool.hpp>
  #include <boost/mpl/and.hpp>
  #include <boost/mpl/or.hpp>
  #include <boost/preprocessor/cat.hpp>
  #include <boost/preprocessor/repetition/repeat.hpp>
  
  namespace boost { namespace spirit { namespace qi { namespace detail
  {
      // Helper meta-function allowing to evaluate weak substitutability and
      // negate the result if the predicate (Sequence) is not true
      template <typename Sequence, typename Attribute, typename ValueType>
      struct negate_weak_substitute_if_not
        : mpl::if_<
              Sequence
            , typename traits::is_weak_substitute<Attribute, ValueType>::type
            , typename mpl::not_<
                  traits::is_weak_substitute<Attribute, ValueType> 
              >::type>
      {};
  
      // pass_through_container: utility to check decide whether a provided 
      // container attribute needs to be passed through to the current component 
      // or of we need to split the container by passing along instances of its
      // value type
  
      // if the expected attribute of the current component is neither a Fusion 
      // sequence nor a container, we will pass through the provided container 
      // only if its value type is not compatible with the component
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence, typename Enable = void>
      struct pass_through_container_base
        : negate_weak_substitute_if_not<Sequence, Attribute, ValueType>
      {};
  
      // Specialization for fusion sequences, in this case we check whether all
      // the types in the sequence are convertible to the lhs attribute.
      // 
      // We return false if the rhs attribute itself is a fusion sequence, which
      // is compatible with the LHS sequence (we want to pass through this 
      // attribute without it being split apart).
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence = mpl::true_>
      struct not_compatible_element
        : mpl::and_<
              negate_weak_substitute_if_not<Sequence, Attribute, Container>
            , negate_weak_substitute_if_not<Sequence, Attribute, ValueType> >
      {};
  
      // If the value type of the container is not a Fusion sequence, we pass
      // through the container if each of the elements of the Attribute 
      // sequence is compatible with either the container or its value type.
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence
        , bool IsSequence = fusion::traits::is_sequence<ValueType>::value>
      struct pass_through_container_fusion_sequence
      {
          typedef typename mpl::find_if<
              Attribute, not_compatible_element<Container, ValueType, mpl::_1>
          >::type iter;
          typedef typename mpl::end<Attribute>::type end;
  
          typedef typename is_same<iter, end>::type type;
      };
  
      // If both, the Attribute and the value type of the provided container
      // are Fusion sequences, we pass the container only if the two 
      // sequences are not compatible.
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence>
      struct pass_through_container_fusion_sequence<
              Container, ValueType, Attribute, Sequence, true>
      {
          typedef typename mpl::find_if<
              Attribute
            , not_compatible_element<Container, ValueType, mpl::_1, Sequence>
          >::type iter;
          typedef typename mpl::end<Attribute>::type end;
  
          typedef typename is_same<iter, end>::type type;
      };
  
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence>
      struct pass_through_container_base<Container, ValueType, Attribute
            , Sequence
            , typename enable_if<fusion::traits::is_sequence<Attribute> >::type>
        : pass_through_container_fusion_sequence<
              Container, ValueType, Attribute, Sequence>
      {};
  
      // Specialization for containers
      //
      // If the value type of the attribute of the current component is not
      // a Fusion sequence, we have to pass through the provided container if 
      // both are compatible.
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence, typename AttributeValueType
        , bool IsSequence = fusion::traits::is_sequence<AttributeValueType>::value>
      struct pass_through_container_container
        : mpl::or_<
              traits::is_weak_substitute<Attribute, Container> 
            , traits::is_weak_substitute<AttributeValueType, Container> >
      {};
  
      // If the value type of the exposed container attribute is a Fusion
      // sequence, we use the already existing logic for those.
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence, typename AttributeValueType>
      struct pass_through_container_container<
              Container, ValueType, Attribute, Sequence, AttributeValueType, true>
        : pass_through_container_fusion_sequence<
              Container, ValueType, AttributeValueType, Sequence>
      {};
  
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence>
      struct pass_through_container_base<
              Container, ValueType, Attribute, Sequence
            , typename enable_if<traits::is_container<Attribute> >::type>
        : detail::pass_through_container_container<
              Container, ValueType, Attribute, Sequence
            , typename traits::container_value<Attribute>::type>
      {};
  
      // Specialization for exposed optional attributes
      //
      // If the type embedded in the exposed optional is not a Fusion 
      // sequence we pass through the container attribute if it is compatible
      // either to the optionals embedded type or to the containers value 
      // type.
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence
        , bool IsSequence = fusion::traits::is_sequence<Attribute>::value>
      struct pass_through_container_optional
        : mpl::or_<
              traits::is_weak_substitute<Attribute, Container> 
            , traits::is_weak_substitute<Attribute, ValueType> >
      {};
  
      // If the embedded type of the exposed optional attribute is a Fusion
      // sequence, we use the already existing logic for those.
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence>
      struct pass_through_container_optional<
                  Container, ValueType, Attribute, Sequence, true>
        : pass_through_container_fusion_sequence<
              Container, ValueType, Attribute, Sequence>
      {};
  
      ///////////////////////////////////////////////////////////////////////////
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence>
      struct pass_through_container
        : pass_through_container_base<Container, ValueType, Attribute, Sequence> 
      {};
  
      // Handle optional attributes
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence>
      struct pass_through_container<
                  Container, ValueType, boost::optional<Attribute>, Sequence>
        : pass_through_container_optional<
              Container, ValueType, Attribute, Sequence> 
      {};
  
      // If both, the containers value type and the exposed attribute type are
      // optionals we are allowed to pass through the the container only if the
      // embedded types of those optionals are not compatible.
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence>
      struct pass_through_container<
              Container, boost::optional<ValueType>, boost::optional<Attribute>
            , Sequence>
        : mpl::not_<traits::is_weak_substitute<Attribute, ValueType> > 
      {};
  
      // Specialization for exposed variant attributes
      // 
      // We pass through the container attribute if at least one of the embedded 
      // types in the variant requires to pass through the attribute
  
  #define BOOST_SPIRIT_PASS_THROUGH_CONTAINER(z, N, _)                          \
      pass_through_container<Container, ValueType,                              \
          BOOST_PP_CAT(T, N), Sequence>::type::value ||                         \
      /***/
  
      // make sure unused variant parameters do not affect the outcome
      template <typename Container, typename ValueType, typename Sequence>
      struct pass_through_container<Container, ValueType
            , boost::detail::variant::void_, Sequence>
        : mpl::false_
      {};
  
      template <typename Container, typename ValueType, typename Sequence
        , BOOST_VARIANT_ENUM_PARAMS(typename T)>
      struct pass_through_container<Container, ValueType
            , boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>, Sequence>
        : mpl::bool_<BOOST_PP_REPEAT(BOOST_VARIANT_LIMIT_TYPES
            , BOOST_SPIRIT_PASS_THROUGH_CONTAINER, _) false>
      {};
  
  #undef BOOST_SPIRIT_PASS_THROUGH_CONTAINER
  }}}}
  
  ///////////////////////////////////////////////////////////////////////////////
  namespace boost { namespace spirit { namespace traits
  {
      ///////////////////////////////////////////////////////////////////////////
      // forwarding customization point for domain qi::domain
      template <typename Container, typename ValueType, typename Attribute
        , typename Sequence>
      struct pass_through_container<
              Container, ValueType, Attribute, Sequence, qi::domain>
        : qi::detail::pass_through_container<
              Container, ValueType, Attribute, Sequence>
      {};
  }}}
  
  namespace boost { namespace spirit { namespace qi { namespace detail
  {
      ///////////////////////////////////////////////////////////////////////////
      // This function handles the case where the attribute (Attr) given
      // the sequence is an STL container. This is a wrapper around F.
      // The function F does the actual parsing.
      template <typename F, typename Attr, typename Sequence>
      struct pass_container
      {
          typedef typename F::context_type context_type;
          typedef typename F::iterator_type iterator_type;
  
          pass_container(F const& f, Attr& attr)
            : f(f), attr(attr) {}
  
          // this is for the case when the current element exposes an attribute
          // which is pushed back onto the container
          template <typename Component>
          bool dispatch_container(Component const& component, mpl::false_) const
          {
              // synthesized attribute needs to be default constructed
              typename traits::container_value<Attr>::type val =
                  typename traits::container_value<Attr>::type();
  
              iterator_type save = f.first;
              bool r = f(component, val);
              if (!r)
              {
                  // push the parsed value into our attribute
                  r = !traits::push_back(attr, val);
                  if (r)
                      f.first = save;
              }
              return r;
          }
  
          // this is for the case when the current element is able to handle an 
          // attribute which is a container itself, this element will push its 
          // data directly into the attribute container
          template <typename Component>
          bool dispatch_container(Component const& component, mpl::true_) const
          {
              return f(component, attr);
          }
  
          ///////////////////////////////////////////////////////////////////////
          // this is for the case when the current element doesn't expect an 
          // attribute
          template <typename Component>
          bool dispatch_attribute(Component const& component, mpl::false_) const
          {
              return f(component, unused);
          }
  
          // the current element expects an attribute
          template <typename Component>
          bool dispatch_attribute(Component const& component, mpl::true_) const
          {
              typedef typename traits::container_value<Attr>::type value_type;
              typedef typename traits::attribute_of<
                  Component, context_type, iterator_type>::type
              rhs_attribute;
  
              // this predicate detects, whether the attribute of the current 
              // element is a substitute for the value type of the container
              // attribute 
              typedef mpl::and_<
                  traits::handles_container<
                      Component, Attr, context_type, iterator_type> 
                , traits::pass_through_container<
                      Attr, value_type, rhs_attribute, Sequence, qi::domain>
              > predicate;
  
              return dispatch_container(component, predicate());
          }
  
          // Dispatches to dispatch_main depending on the attribute type
          // of the Component
          template <typename Component>
          bool operator()(Component const& component) const
          {
              // we need to dispatch depending on the type of the attribute
              // of the current element (component). If this is has no attribute
              // we shouldn't pass an attribute at all.
              typedef typename traits::not_is_unused<
                  typename traits::attribute_of<
                      Component, context_type, iterator_type
                  >::type
              >::type predicate;
  
              // ensure the attribute is actually a container type
              traits::make_container(attr);
  
              return dispatch_attribute(component, predicate());
          }
  
          F f;
          Attr& attr;
  
      private:
          // silence MSVC warning C4512: assignment operator could not be generated
          pass_container& operator= (pass_container const&);
      };
  
      ///////////////////////////////////////////////////////////////////////////
      // Utility function to make a pass_container for container components 
      // (kleene, list, plus, repeat)
      template <typename F, typename Attr>
      inline pass_container<F, Attr, mpl::false_>
      make_pass_container(F const& f, Attr& attr)
      {
          return pass_container<F, Attr, mpl::false_>(f, attr);
      }
  
      // Utility function to make a pass_container for sequences
      template <typename F, typename Attr>
      inline pass_container<F, Attr, mpl::true_>
      make_sequence_pass_container(F const& f, Attr& attr)
      {
          return pass_container<F, Attr, mpl::true_>(f, attr);
      }
  }}}}
  
  #endif
  
  