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