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Filename : permutation.hpp
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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)
=============================================================================*/
#ifndef BOOST_SPIRIT_QI_OPERATOR_PERMUTATION_HPP
#define BOOST_SPIRIT_QI_OPERATOR_PERMUTATION_HPP

#if defined(_MSC_VER)
#pragma once
#endif

#include <boost/spirit/home/qi/meta_compiler.hpp>
#include <boost/spirit/home/qi/detail/permute_function.hpp>
#include <boost/spirit/home/qi/detail/attributes.hpp>
#include <boost/spirit/home/support/algorithm/any_if_ns.hpp>
#include <boost/spirit/home/support/detail/what_function.hpp>
#include <boost/spirit/home/support/has_semantic_action.hpp>
#include <boost/spirit/home/support/handles_container.hpp>
#include <boost/spirit/home/support/info.hpp>
#include <boost/fusion/include/size.hpp>
#include <boost/optional.hpp>
#include <boost/array.hpp>
#include <boost/proto/operators.hpp>
#include <boost/proto/tags.hpp>

namespace boost { namespace spirit
{
    ///////////////////////////////////////////////////////////////////////////
    // Enablers
    ///////////////////////////////////////////////////////////////////////////
    template <>
    struct use_operator<qi::domain, proto::tag::bitwise_xor> // enables ^
      : mpl::true_ {};

    template <>
    struct flatten_tree<qi::domain, proto::tag::bitwise_xor> // flattens ^
      : mpl::true_ {};
}}

namespace boost { namespace spirit { namespace qi
{
    template <typename Elements>
    struct permutation : nary_parser<permutation<Elements> >
    {
        template <typename Context, typename Iterator>
        struct attribute
        {
            // Put all the element attributes in a tuple,
            // wrapping each element in a boost::optional
            typedef typename traits::build_attribute_sequence<
                Elements, Context, traits::permutation_attribute_transform
              , Iterator, qi::domain
            >::type all_attributes;

            // Now, build a fusion vector over the attributes. Note
            // that build_fusion_vector 1) removes all unused attributes
            // and 2) may return unused_type if all elements have
            // unused_type(s).
            typedef typename
                traits::build_fusion_vector<all_attributes>::type
            type;
        };

        permutation(Elements const& elements_)
          : elements(elements_) {}

        template <typename Iterator, typename Context
          , typename Skipper, typename Attribute>
        bool parse(Iterator& first, Iterator const& last
          , Context& context, Skipper const& skipper
          , Attribute& attr_) const
        {
            typedef traits::attribute_not_unused<Context, Iterator> predicate;
            detail::permute_function<Iterator, Context, Skipper>
                f(first, last, context, skipper);

            boost::array<bool, fusion::result_of::size<Elements>::value> flags;
            flags.fill(false);

            // wrap the attribute in a tuple if it is not a tuple
            typename traits::wrap_if_not_tuple<Attribute>::type attr_local(attr_);

            // We have a bool array 'flags' with one flag for each parser.
            // permute_function sets the slot to true when the corresponding
            // parser successful matches. We loop until there are no more
            // successful parsers.

            bool result = false;
            f.taken = flags.begin();
            while (spirit::any_if_ns(elements, attr_local, f, predicate()))
            {
                f.taken = flags.begin();
                result = true;
            }
            return result;
        }

        template <typename Context>
        info what(Context& context) const
        {
            info result("permutation");
            fusion::for_each(elements,
                spirit::detail::what_function<Context>(result, context));
            return result;
        }

        Elements elements;
    };

    ///////////////////////////////////////////////////////////////////////////
    // Parser generators: make_xxx function (objects)
    ///////////////////////////////////////////////////////////////////////////
    template <typename Elements, typename Modifiers>
    struct make_composite<proto::tag::bitwise_xor, Elements, Modifiers>
      : make_nary_composite<Elements, permutation>
    {};
}}}

namespace boost { namespace spirit { namespace traits
{
    ///////////////////////////////////////////////////////////////////////////
    // We specialize this for permutation (see support/attributes.hpp).
    // For permutation, we only wrap the attribute in a tuple IFF
    // it is not already a fusion tuple.
    template <typename Elements, typename Attribute>
    struct pass_attribute<qi::permutation<Elements>, Attribute>
      : wrap_if_not_tuple<Attribute> {};

    ///////////////////////////////////////////////////////////////////////////
    template <typename Elements>
    struct has_semantic_action<qi::permutation<Elements> >
      : nary_has_semantic_action<Elements> {};

    ///////////////////////////////////////////////////////////////////////////
    template <typename Elements, typename Attribute, typename Context
      , typename Iterator>
    struct handles_container<qi::permutation<Elements>, Attribute, Context
      , Iterator>
      : nary_handles_container<Elements, Attribute, Context, Iterator> {};
}}}

#endif