x3/directive/seek.hpp

0001 /*=============================================================================
0002     Copyright (c) 2011 Jamboree
0003     Copyright (c) 2014 Lee Clagett
0004
0005     Distributed under the Boost Software License, Version 1.0. (See accompanying
0006     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0007 ==============================================================================*/
0008 #if !defined(BOOST_SPIRIT_X3_SEEK_APRIL_13_2014_1920PM)
0009 #define BOOST_SPIRIT_X3_SEEK_APRIL_13_2014_1920PM
0010
0011 #include <boost/spirit/home/x3/core/parser.hpp>
0012
0013 namespace boost { namespace spirit { namespace x3
0014 {
0015     template<typename Subject>
0016     struct seek_directive : unary_parser<Subject, seek_directive<Subject>>
0017     {
0018         typedef unary_parser<Subject, seek_directive<Subject>> base_type;
0019         static bool const is_pass_through_unary = true;
0020         static bool const handles_container = Subject::handles_container;
0021
0022         constexpr seek_directive(Subject const& subject) :
0023             base_type(subject) {}
0024
0025         template<typename Iterator, typename Context
0026           , typename RContext, typename Attribute>
0027         bool parse(
0028             Iterator& first, Iterator const& last
0029           , Context const& context, RContext& rcontext, Attribute& attr) const
0030         {
0031             for (Iterator current(first);; ++current)
0032             {
0033                 if (this->subject.parse(current, last, context, rcontext, attr))
0034                 {
0035                     first = current;
0036                     return true;
0037                 }
0038
0039                 // fail only after subject fails & no input
0040                 if (current == last)
0041                     return false;
0042             }
0043         }
0044     };
0045
0046     struct seek_gen
0047     {
0048         template<typename Subject>
0049         constexpr seek_directive<typename extension::as_parser<Subject>::value_type>
0050         operator[](Subject const& subject) const
0051         {
0052             return { as_parser(subject) };
0053         }
0054     };
0055
0056     constexpr auto seek = seek_gen{};
0057 }}}
0058
0059 #endif