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/*=============================================================================
Copyright (c) 2001-2014 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(BOOST_SPIRIT_X3_OPTIONAL_MARCH_23_2007_1117PM)
#define BOOST_SPIRIT_X3_OPTIONAL_MARCH_23_2007_1117PM
#include <boost/spirit/home/x3/core/proxy.hpp>
#include <boost/spirit/home/x3/core/detail/parse_into_container.hpp>
#include <boost/spirit/home/x3/support/traits/attribute_of.hpp>
#include <boost/spirit/home/x3/support/traits/move_to.hpp>
#include <boost/spirit/home/x3/support/traits/optional_traits.hpp>
#include <boost/spirit/home/x3/support/traits/attribute_category.hpp>
namespace boost { namespace spirit { namespace x3
{
template <typename Subject>
struct optional : proxy<Subject, optional<Subject>>
{
typedef proxy<Subject, optional<Subject>> base_type;
static bool const handles_container = true;
optional(Subject const& subject)
: base_type(subject) {}
using base_type::parse_subject;
// Attribute is a container
template <typename Iterator, typename Context
, typename RContext, typename Attribute>
bool parse_subject(Iterator& first, Iterator const& last
, Context const& context, RContext& rcontext, Attribute& attr
, traits::container_attribute) const
{
detail::parse_into_container(
this->subject, first, last, context, rcontext, attr);
return true;
}
// Attribute is an optional
template <typename Iterator, typename Context
, typename RContext, typename Attribute>
bool parse_subject(Iterator& first, Iterator const& last
, Context const& context, RContext& rcontext, Attribute& attr
, traits::optional_attribute) const
{
typedef typename
x3::traits::optional_value<Attribute>::type
value_type;
// create a local value
value_type val = value_type();
if (this->subject.parse(first, last, context, rcontext, val))
{
// assign the parsed value into our attribute
x3::traits::move_to(val, attr);
}
return true;
}
};
template <typename Subject>
inline optional<typename extension::as_parser<Subject>::value_type>
operator-(Subject const& subject)
{
return { as_parser(subject) };
}
}}}
namespace boost { namespace spirit { namespace x3 { namespace traits
{
template <typename Subject, typename Context>
struct attribute_of<x3::optional<Subject>, Context>
: build_optional<
typename attribute_of<Subject, Context>::type> {};
}}}}
#endif
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