ceph/src/boost/libs/spirit/classic/example/fundamental/parser_context.cpp

   1 /*=============================================================================
   2     Copyright (c) 2003 Vaclav Vesely
   3     http://spirit.sourceforge.net/
   4
   5     Use, modification and distribution is subject to the Boost Software
   6     License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   7     http://www.boost.org/LICENSE_1_0.txt)
   8 =============================================================================*/
   9 //
  10 //  This example demonstrates usage of the parser_context template with
  11 //  an explicit argument to declare rules with match results different from
  12 //  nil_t. For better understanding, you should read the chapter "In-depth:
  13 //  The Parser Context" in the documentation.
  14 //
  15 //  The default context of non-terminals is the parser_context.
  16 //  The parser_context is a template with one argument AttrT, which is the type
  17 //  of match attribute.
  18 //
  19 //  In this example int_rule is declared as rule with int match attribute's
  20 //  type, so in int_rule variable we can hold any parser, which returns int
  21 //  value. For example int_p or bin_p. And the most important is that we can
  22 //  use returned value in the semantic action binded to the int_rule.
  23 //
  24 //-----------------------------------------------------------------------------
  25 #include <iostream>
  26 #include <boost/cstdlib.hpp>
  27 #include <boost/spirit/include/phoenix1.hpp>
  28 #include <boost/spirit/include/classic_core.hpp>
  29
  30 using namespace std;
  31 using namespace boost;
  32 using namespace phoenix;
  33 using namespace BOOST_SPIRIT_CLASSIC_NS;
  34
  35 //-----------------------------------------------------------------------------
  36
  37 int main()
  38 {
  39     rule<parser_context<int> > int_rule = int_p;
  40
  41     parse(
  42         "123",
  43         // Using a returned value in the semantic action
  44         int_rule[cout << arg1 << endl]
  45     );
  46
  47     return exit_success;
  48 }
  49
  50 //-----------------------------------------------------------------------------
  51