ceph/src/boost/boost/spirit/home/karma/operator/optional.hpp

   1 //  Copyright (c) 2001-2011 Joel de Guzman
   2 //  Copyright (c) 2001-2011 Hartmut Kaiser
   3 //
   4 //  Distributed under the Boost Software License, Version 1.0. (See accompanying
   5 //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #if !defined(SPIRIT_KARMA_OPTIONAL_MARCH_31_2007_0852AM)
   8 #define SPIRIT_KARMA_OPTIONAL_MARCH_31_2007_0852AM
   9
  10 #if defined(_MSC_VER)
  11 #pragma once
  12 #endif
  13
  14 #include <boost/spirit/home/karma/domain.hpp>
  15 #include <boost/spirit/home/karma/generator.hpp>
  16 #include <boost/spirit/home/karma/meta_compiler.hpp>
  17 #include <boost/spirit/home/support/info.hpp>
  18 #include <boost/spirit/home/support/unused.hpp>
  19 #include <boost/spirit/home/karma/detail/attributes.hpp>
  20 #include <boost/spirit/home/support/container.hpp>
  21 #include <boost/spirit/home/support/has_semantic_action.hpp>
  22 #include <boost/spirit/home/support/handles_container.hpp>
  23 #include <boost/mpl/assert.hpp>
  24 #include <boost/optional.hpp>
  25 #include <boost/type_traits/is_convertible.hpp>
  26
  27 namespace boost { namespace spirit
  28 {
  29     ///////////////////////////////////////////////////////////////////////////
  30     // Enablers
  31     ///////////////////////////////////////////////////////////////////////////
  32     template <>
  33     struct use_operator<karma::domain, proto::tag::negate> // enables -g
  34       : mpl::true_ {};
  35
  36 }}
  37
  38 ///////////////////////////////////////////////////////////////////////////////
  39 namespace boost { namespace spirit { namespace karma
  40 {
  41     ///////////////////////////////////////////////////////////////////////////
  42     template <typename Subject>
  43     struct optional : unary_generator<optional<Subject> >
  44     {
  45         typedef Subject subject_type;
  46         typedef typename subject_type::properties properties;
  47
  48         // Build a boost::optional from the subject's attribute. Note
  49         // that boost::optional may return unused_type if the
  50         // subject's attribute is an unused_type.
  51         template <typename Context, typename Iterator = unused_type>
  52         struct attribute
  53           : traits::build_optional<
  54                 typename traits::attribute_of<Subject, Context, Iterator>::type
  55             >
  56         {};
  57
  58         optional(Subject const& subject)
  59           : subject(subject) {}
  60
  61         template <
  62             typename OutputIterator, typename Context, typename Delimiter
  63           , typename Attribute>
  64         bool generate(OutputIterator& sink, Context& ctx
  65           , Delimiter const& d, Attribute const& attr) const
  66         {
  67             if (traits::has_optional_value(attr))
  68                 subject.generate(sink, ctx, d, traits::optional_value(attr));
  69             return sink_is_good(sink);
  70         }
  71
  72         template <typename Context>
  73         info what(Context& context) const
  74         {
  75             return info("optional", subject.what(context));
  76         }
  77
  78         Subject subject;
  79     };
  80
  81     ///////////////////////////////////////////////////////////////////////////
  82     // Generator generators: make_xxx function (objects)
  83     ///////////////////////////////////////////////////////////////////////////
  84     template <typename Elements, typename Modifiers>
  85     struct make_composite<proto::tag::negate, Elements, Modifiers>
  86       : make_unary_composite<Elements, optional> {};
  87
  88 }}}
  89
  90 namespace boost { namespace spirit { namespace traits
  91 {
  92     ///////////////////////////////////////////////////////////////////////////
  93     template <typename Subject>
  94     struct has_semantic_action<karma::optional<Subject> >
  95       : unary_has_semantic_action<Subject> {};
  96
  97     ///////////////////////////////////////////////////////////////////////////
  98     template <typename Subject, typename Attribute, typename Context
  99       , typename Iterator>
 100     struct handles_container<karma::optional<Subject>, Attribute, Context
 101           , Iterator>
 102       : mpl::true_ {};
 103 }}}
 104
 105 #endif