karma/directive/omit.hpp

0001 //  Copyright (c) 2001-2011 Hartmut Kaiser
0002 //
0003 //  Distributed under the Boost Software License, Version 1.0. (See accompanying
0004 //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0005
0006 #ifndef BOOST_SPIRIT_KARMA_DIRECTIVE_OMIT_HPP
0007 #define BOOST_SPIRIT_KARMA_DIRECTIVE_OMIT_HPP
0008
0009 #if defined(_MSC_VER)
0010 #pragma once
0011 #endif
0012
0013 #include <boost/spirit/home/karma/meta_compiler.hpp>
0014 #include <boost/spirit/home/karma/generator.hpp>
0015 #include <boost/spirit/home/karma/domain.hpp>
0016 #include <boost/spirit/home/support/unused.hpp>
0017 #include <boost/spirit/home/support/info.hpp>
0018 #include <boost/spirit/home/support/common_terminals.hpp>
0019 #include <boost/spirit/home/support/has_semantic_action.hpp>
0020 #include <boost/spirit/home/support/handles_container.hpp>
0021 #include <boost/spirit/home/karma/detail/attributes.hpp>
0022 #include <boost/spirit/home/karma/detail/output_iterator.hpp>
0023
0024 namespace boost { namespace spirit
0025 {
0026     ///////////////////////////////////////////////////////////////////////////
0027     // Enablers
0028     ///////////////////////////////////////////////////////////////////////////
0029     template <>
0030     struct use_directive<karma::domain, tag::omit> // enables omit
0031       : mpl::true_ {};
0032
0033     template <>
0034     struct use_directive<karma::domain, tag::skip> // enables skip
0035       : mpl::true_ {};
0036 }}
0037
0038 namespace boost { namespace spirit { namespace karma
0039 {
0040 #ifndef BOOST_SPIRIT_NO_PREDEFINED_TERMINALS
0041     using spirit::omit;
0042     using spirit::skip;
0043 #endif
0044     using spirit::omit_type;
0045     using spirit::skip_type;
0046
0047     ///////////////////////////////////////////////////////////////////////////
0048     // omit_directive consumes the attribute of subject generator without
0049     // generating anything
0050     ///////////////////////////////////////////////////////////////////////////
0051     template <typename Subject, bool Execute>
0052     struct omit_directive : unary_generator<omit_directive<Subject, Execute> >
0053     {
0054         typedef Subject subject_type;
0055
0056         typedef mpl::int_<
0057             generator_properties::disabling | subject_type::properties::value
0058         > properties;
0059
0060         omit_directive(Subject const& subject)
0061           : subject(subject) {}
0062
0063         template <typename Context, typename Iterator = unused_type>
0064         struct attribute
0065           : traits::attribute_of<subject_type, Context, Iterator>
0066         {};
0067
0068         template <typename OutputIterator, typename Context, typename Delimiter
0069           , typename Attribute>
0070         bool generate(OutputIterator& sink, Context& ctx, Delimiter const& d
0071           , Attribute const& attr) const
0072         {
0073             // We need to actually compile the output operation as we don't
0074             // have any other means to verify, whether the passed attribute is
0075             // compatible with the subject.
0076
0077 #if defined(_MSC_VER) && _MSC_VER < 1900
0078 # pragma warning(push)
0079 # pragma warning(disable: 4127) // conditional expression is constant
0080 #endif
0081             // omit[] will execute the code, while skip[] doesn't execute it
0082             if (Execute) {
0083 #if defined(_MSC_VER) && _MSC_VER < 1900
0084 # pragma warning(pop)
0085 #endif
0086                 // wrap the given output iterator to avoid output
0087                 detail::disable_output<OutputIterator> disable(sink);
0088                 return subject.generate(sink, ctx, d, attr);
0089             }
0090             return true;
0091         }
0092
0093         template <typename Context>
0094         info what(Context& context) const
0095         {
0096             return info(Execute ? "omit" : "skip", subject.what(context));
0097         }
0098
0099         Subject subject;
0100     };
0101
0102     ///////////////////////////////////////////////////////////////////////////
0103     // Generator generators: make_xxx function (objects)
0104     ///////////////////////////////////////////////////////////////////////////
0105     template <typename Subject, typename Modifiers>
0106     struct make_directive<tag::omit, Subject, Modifiers>
0107     {
0108         typedef omit_directive<Subject, true> result_type;
0109         result_type operator()(unused_type, Subject const& subject
0110           , unused_type) const
0111         {
0112             return result_type(subject);
0113         }
0114     };
0115
0116     template <typename Subject, typename Modifiers>
0117     struct make_directive<tag::skip, Subject, Modifiers>
0118     {
0119         typedef omit_directive<Subject, false> result_type;
0120         result_type operator()(unused_type, Subject const& subject
0121           , unused_type) const
0122         {
0123             return result_type(subject);
0124         }
0125     };
0126 }}}
0127
0128 namespace boost { namespace spirit { namespace traits
0129 {
0130     ///////////////////////////////////////////////////////////////////////////
0131     template <typename Subject, bool Execute>
0132     struct has_semantic_action<karma::omit_directive<Subject, Execute> >
0133       : unary_has_semantic_action<Subject> {};
0134
0135     ///////////////////////////////////////////////////////////////////////////
0136     template <typename Subject, bool Execute, typename Attribute
0137         , typename Context, typename Iterator>
0138     struct handles_container<karma::omit_directive<Subject, Execute>, Attribute
0139         , Context, Iterator>
0140       : unary_handles_container<Subject, Attribute, Context, Iterator> {};
0141 }}}
0142
0143 #endif