Chris@102: /*=============================================================================
Chris@102:     Copyright (c) 2001-2014 Joel de Guzman
Chris@102:     Copyright (c) 2001-2011 Hartmut Kaiser
Chris@102: 
Chris@102:     Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@102:     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@102: =============================================================================*/
Chris@102: #if !defined(SPIRIT_OPTIONAL_MARCH_23_2007_1117PM)
Chris@102: #define SPIRIT_OPTIONAL_MARCH_23_2007_1117PM
Chris@102: 
Chris@102: #if defined(_MSC_VER)
Chris@102: #pragma once
Chris@102: #endif
Chris@102: 
Chris@102: #include <boost/spirit/home/x3/core/proxy.hpp>
Chris@102: #include <boost/spirit/home/x3/core/detail/parse_into_container.hpp>
Chris@102: #include <boost/spirit/home/x3/support/traits/attribute_of.hpp>
Chris@102: #include <boost/spirit/home/x3/support/traits/move_to.hpp>
Chris@102: #include <boost/spirit/home/x3/support/traits/optional_traits.hpp>
Chris@102: #include <boost/spirit/home/x3/support/traits/attribute_category.hpp>
Chris@102: 
Chris@102: namespace boost { namespace spirit { namespace x3
Chris@102: {
Chris@102:     template <typename Subject>
Chris@102:     struct optional : proxy<Subject, optional<Subject>>
Chris@102:     {
Chris@102:         typedef proxy<Subject, optional<Subject>> base_type;
Chris@102:         static bool const handles_container = true;
Chris@102: 
Chris@102:         optional(Subject const& subject)
Chris@102:           : base_type(subject) {}
Chris@102: 
Chris@102:         using base_type::parse_subject;
Chris@102: 
Chris@102:         // Attribute is a container
Chris@102:         template <typename Iterator, typename Context
Chris@102:           , typename RContext, typename Attribute>
Chris@102:         bool parse_subject(Iterator& first, Iterator const& last
Chris@102:           , Context const& context, RContext& rcontext, Attribute& attr
Chris@102:           , traits::container_attribute) const
Chris@102:         {
Chris@102:             detail::parse_into_container(
Chris@102:                 this->subject, first, last, context, rcontext, attr);
Chris@102:             return true;
Chris@102:         }
Chris@102: 
Chris@102:         // Attribute is an optional
Chris@102:         template <typename Iterator, typename Context
Chris@102:           , typename RContext, typename Attribute>
Chris@102:         bool parse_subject(Iterator& first, Iterator const& last
Chris@102:           , Context const& context, RContext& rcontext, Attribute& attr
Chris@102:           , traits::optional_attribute) const
Chris@102:         {
Chris@102:             typedef typename
Chris@102:                 x3::traits::optional_value<Attribute>::type
Chris@102:             value_type;
Chris@102: 
Chris@102:             // create a local value
Chris@102:             value_type val = value_type();
Chris@102: 
Chris@102:             if (this->subject.parse(first, last, context, rcontext, val))
Chris@102:             {
Chris@102:                 // assign the parsed value into our attribute
Chris@102:                 x3::traits::move_to(val, attr);
Chris@102:             }
Chris@102:             return true;
Chris@102:         }
Chris@102:     };
Chris@102: 
Chris@102:     template <typename Subject>
Chris@102:     inline optional<typename extension::as_parser<Subject>::value_type>
Chris@102:     operator-(Subject const& subject)
Chris@102:     {
Chris@102:         return {as_parser(subject)};
Chris@102:     }
Chris@102: }}}
Chris@102: 
Chris@102: namespace boost { namespace spirit { namespace x3 { namespace traits
Chris@102: {
Chris@102:     template <typename Subject, typename Context>
Chris@102:     struct attribute_of<x3::optional<Subject>, Context>
Chris@102:         : build_optional<
Chris@102:             typename attribute_of<Subject, Context>::type> {};
Chris@102: }}}}
Chris@102: 
Chris@102: #endif