100 lines
2.8 KiB
C++
Executable File
100 lines
2.8 KiB
C++
Executable File
// Copyright (c) 2001-2007 Joel de Guzman
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// Copyright (c) 2001-2008 Hartmut Kaiser
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#if !defined(SPIRIT_KARMA_OPTIONAL_MARCH_31_2007_0852AM)
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#define SPIRIT_KARMA_OPTIONAL_MARCH_31_2007_0852AM
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#if defined(_MSC_VER) && (_MSC_VER >= 1020)
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#pragma once // MS compatible compilers support #pragma once
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#endif
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#include <boost/spirit/home/support/component.hpp>
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#include <boost/spirit/home/support/attribute_transform.hpp>
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#include <boost/mpl/assert.hpp>
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#include <boost/optional.hpp>
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namespace boost { namespace spirit { namespace karma
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{
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namespace detail
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{
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template <typename Parameter>
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inline bool
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optional_is_valid(boost::optional<Parameter> const& opt)
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{
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return opt;
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}
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inline bool
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optional_is_valid(unused_type)
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{
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return true;
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}
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template <typename Parameter>
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inline Parameter const&
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optional_get(boost::optional<Parameter> const& opt)
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{
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return get(opt) ;
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}
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inline unused_type
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optional_get(unused_type)
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{
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return unused;
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}
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}
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struct optional
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{
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template <typename T>
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struct build_attribute_container
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{
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typedef boost::optional<T> type;
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};
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template <typename Component, typename Context, typename Iterator>
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struct attribute :
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build_container<optional, Component, Iterator, Context>
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{
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};
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template <typename Component, typename OutputIterator,
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typename Context, typename Delimiter, typename Parameter>
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static bool
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generate(Component const& component, OutputIterator& sink,
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Context& ctx, Delimiter const& d, Parameter const& param)
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{
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typedef typename
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result_of::subject<Component>::type::director
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director;
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if (detail::optional_is_valid(param))
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{
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director::generate(subject(component), sink, ctx, d,
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detail::optional_get(param));
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}
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return true;
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}
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template <typename Component, typename Context>
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static std::string what(Component const& component, Context const& ctx)
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{
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std::string result = "optional[";
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typedef typename
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spirit::result_of::subject<Component>::type::director
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director;
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result += director::what(spirit::subject(component), ctx);
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result += "]";
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return result;
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}
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};
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}}}
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#endif
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