// 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) #if !defined(SPIRIT_KARMA_OPTIONAL_MARCH_31_2007_0852AM) #define SPIRIT_KARMA_OPTIONAL_MARCH_31_2007_0852AM #if defined(_MSC_VER) #pragma once #endif #include <boost/spirit/home/karma/domain.hpp> #include <boost/spirit/home/karma/generator.hpp> #include <boost/spirit/home/karma/meta_compiler.hpp> #include <boost/spirit/home/support/info.hpp> #include <boost/spirit/home/support/unused.hpp> #include <boost/spirit/home/karma/detail/attributes.hpp> #include <boost/spirit/home/support/container.hpp> #include <boost/spirit/home/support/has_semantic_action.hpp> #include <boost/spirit/home/support/handles_container.hpp> #include <boost/mpl/assert.hpp> #include <boost/optional.hpp> #include <boost/type_traits/is_convertible.hpp> namespace boost { namespace spirit { /////////////////////////////////////////////////////////////////////////// // Enablers /////////////////////////////////////////////////////////////////////////// template <> struct use_operator<karma::domain, proto::tag::negate> // enables -g : mpl::true_ {}; }} /////////////////////////////////////////////////////////////////////////////// namespace boost { namespace spirit { namespace karma { /////////////////////////////////////////////////////////////////////////// template <typename Subject> struct optional : unary_generator<optional<Subject> > { typedef Subject subject_type; typedef typename subject_type::properties properties; // 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. template <typename Context, typename Iterator = unused_type> struct attribute : traits::build_optional< typename traits::attribute_of<Subject, Context, Iterator>::type > {}; optional(Subject const& subject) : subject(subject) {} template < typename OutputIterator, typename Context, typename Delimiter , typename Attribute> bool generate(OutputIterator& sink, Context& ctx , Delimiter const& d, Attribute const& attr) const { if (traits::has_optional_value(attr)) subject.generate(sink, ctx, d, traits::optional_value(attr)); return sink_is_good(sink); } template <typename Context> info what(Context& context) const { return info("optional", subject.what(context)); } Subject subject; }; /////////////////////////////////////////////////////////////////////////// // Generator 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<karma::optional<Subject> > : unary_has_semantic_action<Subject> {}; /////////////////////////////////////////////////////////////////////////// template <typename Subject, typename Attribute, typename Context , typename Iterator> struct handles_container<karma::optional<Subject>, Attribute, Context , Iterator> : mpl::true_ {}; }}} #endif