Chris@16: /*=============================================================================
Chris@16:     Copyright (c) 2001-2011 Joel de Guzman
Chris@16:     Copyright (c) 2001-2011 Hartmut Kaiser
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: #if !defined(SPIRIT_OPTIONAL_MARCH_23_2007_1117PM)
Chris@16: #define SPIRIT_OPTIONAL_MARCH_23_2007_1117PM
Chris@16: 
Chris@16: #if defined(_MSC_VER)
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/spirit/home/support/unused.hpp>
Chris@16: #include <boost/spirit/home/qi/detail/attributes.hpp>
Chris@16: #include <boost/spirit/home/support/has_semantic_action.hpp>
Chris@16: #include <boost/spirit/home/support/handles_container.hpp>
Chris@16: #include <boost/spirit/home/support/info.hpp>
Chris@16: #include <boost/spirit/home/support/container.hpp>
Chris@16: #include <boost/spirit/home/qi/parser.hpp>
Chris@16: #include <boost/spirit/home/qi/meta_compiler.hpp>
Chris@16: #include <boost/spirit/home/qi/detail/assign_to.hpp>
Chris@16: #include <boost/optional.hpp>
Chris@16: #include <vector>
Chris@16: 
Chris@16: namespace boost { namespace spirit
Chris@16: {
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     // Enablers
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     template <>
Chris@16:     struct use_operator<qi::domain, proto::tag::negate> // enables -p
Chris@16:       : mpl::true_ {};
Chris@16: }}
Chris@16: 
Chris@16: namespace boost { namespace spirit { namespace qi
Chris@16: {
Chris@16:     template <typename Subject>
Chris@16:     struct optional : unary_parser<optional<Subject> >
Chris@16:     {
Chris@16:         typedef Subject subject_type;
Chris@16: 
Chris@16:         template <typename Context, typename Iterator>
Chris@16:         struct attribute
Chris@16:         {
Chris@16:             // Build a boost::optional from the subject's attribute. Note
Chris@16:             // that boost::optional may return unused_type if the
Chris@16:             // subject's attribute is an unused_type.
Chris@16:             typedef typename
Chris@16:                 traits::build_optional<
Chris@16:                     typename traits::
Chris@16:                         attribute_of<Subject, Context, Iterator>::type
Chris@16:                 >::type
Chris@16:             type;
Chris@16:         };
Chris@16: 
Chris@16:         optional(Subject const& subject_)
Chris@16:           : subject(subject_) {}
Chris@16: 
Chris@16:         template <typename Iterator, typename Context
Chris@16:           , typename Skipper, typename Attribute>
Chris@16:         bool parse_impl(Iterator& first, Iterator const& last
Chris@16:           , Context& context, Skipper const& skipper
Chris@16:           , Attribute& attr_, mpl::false_) const
Chris@16:         {
Chris@16:             // create a local value if Attribute is not unused_type
Chris@101:             typename spirit::result_of::optional_value<Attribute>::type val =
Chris@16:                 typename spirit::result_of::optional_value<Attribute>::type();
Chris@16: 
Chris@16:             if (subject.parse(first, last, context, skipper, val))
Chris@16:             {
Chris@16:                 // assign the parsed value into our attribute
Chris@16:                 spirit::traits::assign_to(val, attr_);
Chris@16:             }
Chris@16:             return true;
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Iterator, typename Context
Chris@16:           , typename Skipper, typename Attribute>
Chris@16:         bool parse_impl(Iterator& first, Iterator const& last
Chris@16:           , Context& context, Skipper const& skipper
Chris@16:           , Attribute& attr_, mpl::true_) const
Chris@16:         {
Chris@16:             subject.parse(first, last, context, skipper, attr_);
Chris@16:             return true;
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Iterator, typename Context
Chris@16:           , typename Skipper, typename Attribute>
Chris@16:         bool parse(Iterator& first, Iterator const& last
Chris@16:           , Context& context, Skipper const& skipper
Chris@16:           , Attribute& attr_) const
Chris@16:         {
Chris@101:             typedef typename spirit::result_of::optional_value<Attribute>::type
Chris@16:                 attribute_type;
Chris@16: 
Chris@16:             return parse_impl(first, last, context, skipper, attr_
Chris@16:               , traits::is_container<attribute_type>());
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Context>
Chris@16:         info what(Context& context) const
Chris@16:         {
Chris@16:             return info("optional", subject.what(context));
Chris@16:         }
Chris@16: 
Chris@16:         Subject subject;
Chris@16:     };
Chris@16: 
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     // Parser generators: make_xxx function (objects)
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     template <typename Elements, typename Modifiers>
Chris@16:     struct make_composite<proto::tag::negate, Elements, Modifiers>
Chris@16:       : make_unary_composite<Elements, optional>
Chris@16:     {};
Chris@16: }}}
Chris@16: 
Chris@16: namespace boost { namespace spirit { namespace traits
Chris@16: {
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     template <typename Subject>
Chris@16:     struct has_semantic_action<qi::optional<Subject> >
Chris@16:       : unary_has_semantic_action<Subject> {};
Chris@16: 
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     template <typename Subject, typename Attribute, typename Context
Chris@16:         , typename Iterator>
Chris@16:     struct handles_container<qi::optional<Subject>, Attribute
Chris@16:           , Context, Iterator>
Chris@16:       : mpl::true_ {};
Chris@16: }}}
Chris@16: 
Chris@16: #endif