Boost C++ Libraries

boost/spirit/home/qi/operator/plus.hpp

/*=============================================================================
    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)
=============================================================================*/
#ifndef BOOST_SPIRIT_QI_OPERATOR_PLUS_HPP
#define BOOST_SPIRIT_QI_OPERATOR_PLUS_HPP

#if defined(_MSC_VER)
#pragma once
#endif

#include <boost/spirit/home/qi/meta_compiler.hpp>
#include <boost/spirit/home/qi/parser.hpp>
#include <boost/spirit/home/support/container.hpp>
#include <boost/spirit/home/qi/detail/attributes.hpp>
#include <boost/spirit/home/qi/detail/fail_function.hpp>
#include <boost/spirit/home/qi/detail/pass_container.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/proto/operators.hpp>
#include <boost/proto/tags.hpp>

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

namespace boost { namespace spirit { namespace qi
{
    template <typename Subject>
    struct plus : unary_parser<plus<Subject> >
    {
        typedef Subject subject_type;

        template <typename Context, typename Iterator>
        struct attribute
        {
            // Build a std::vector from the subject's attribute. Note
            // that build_std_vector may return unused_type if the
            // subject's attribute is an unused_type.
            typedef typename
                traits::build_std_vector<
                    typename traits::attribute_of<
                        Subject, Context, Iterator>::type
                >::type
            type;
        };

        plus(Subject const& subject_)
          : subject(subject_) {}

        template <typename F>
        bool parse_container(F f) const
        {
            // in order to succeed we need to match at least one element 
            if (f (subject))
                return false;

            while (!f (subject))
                ;
            return true;
        }

        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 detail::fail_function<Iterator, Context, Skipper>
                fail_function;

            // ensure the attribute is actually a container type
            traits::make_container(attr_);

            Iterator iter = first;
            fail_function f(iter, last, context, skipper);
            if (!parse_container(detail::make_pass_container(f, attr_)))
                return false;

            first = f.first;
            return true;
        }

        template <typename Context>
        info what(Context& context) const
        {
            return info("plus", subject.what(context));
        }

        Subject subject;
    };

    ///////////////////////////////////////////////////////////////////////////
    // Parser generators: make_xxx function (objects)
    ///////////////////////////////////////////////////////////////////////////
    template <typename Elements, typename Modifiers>
    struct make_composite<proto::tag::unary_plus, Elements, Modifiers>
      : make_unary_composite<Elements, plus>
    {};
}}}

namespace boost { namespace spirit { namespace traits
{
    ///////////////////////////////////////////////////////////////////////////
    template <typename Subject>
    struct has_semantic_action<qi::plus<Subject> >
      : unary_has_semantic_action<Subject> {};

    ///////////////////////////////////////////////////////////////////////////
    template <typename Subject, typename Attribute, typename Context
      , typename Iterator>
    struct handles_container<qi::plus<Subject>, Attribute, Context
          , Iterator>
      : mpl::true_ {}; 
}}}

#endif