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

   1 /*=============================================================================
   2     Copyright (c) 2002-2003 Joel de Guzman
   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 //
  11 //  Full calculator example demonstrating Phoenix
  12 //  This is discussed in the "Closures" chapter in the Spirit User's Guide.
  13 //
  14 //  [ JDG 6/29/2002 ]
  15 //
  16 ////////////////////////////////////////////////////////////////////////////
  17 #include <boost/spirit/include/classic_core.hpp>
  18 #include <boost/spirit/include/classic_attribute.hpp>
  19 #include <iostream>
  20 #include <string>
  21
  22 ////////////////////////////////////////////////////////////////////////////
  23 using namespace std;
  24 using namespace BOOST_SPIRIT_CLASSIC_NS;
  25 using namespace phoenix;
  26
  27 ////////////////////////////////////////////////////////////////////////////
  28 //
  29 //  Our calculator grammar using phoenix to do the semantics
  30 //
  31 //  Note:   The top rule propagates the expression result (value) upwards
  32 //          to the calculator grammar self.val closure member which is
  33 //          then visible outside the grammar (i.e. since self.val is the
  34 //          member1 of the closure, it becomes the attribute passed by
  35 //          the calculator to an attached semantic action. See the
  36 //          driver code that uses the calculator below).
  37 //
  38 ////////////////////////////////////////////////////////////////////////////
  39 struct calc_closure : BOOST_SPIRIT_CLASSIC_NS::closure<calc_closure, double>
  40 {
  41     member1 val;
  42 };
  43
  44 struct calculator : public grammar<calculator, calc_closure::context_t>
  45 {
  46     template <typename ScannerT>
  47     struct definition
  48     {
  49         definition(calculator const& self)
  50         {
  51             top = expression[self.val = arg1];
  52
  53             expression
  54                 =   term[expression.val = arg1]
  55                     >> *(   ('+' >> term[expression.val += arg1])
  56                         |   ('-' >> term[expression.val -= arg1])
  57                         )
  58                 ;
  59
  60             term
  61                 =   factor[term.val = arg1]
  62                     >> *(   ('*' >> factor[term.val *= arg1])
  63                         |   ('/' >> factor[term.val /= arg1])
  64                         )
  65                 ;
  66
  67             factor
  68                 =   ureal_p[factor.val = arg1]
  69                 |   '(' >> expression[factor.val = arg1] >> ')'
  70                 |   ('-' >> factor[factor.val = -arg1])
  71                 |   ('+' >> factor[factor.val = arg1])
  72                 ;
  73         }
  74
  75         typedef rule<ScannerT, calc_closure::context_t> rule_t;
  76         rule_t expression, term, factor;
  77         rule<ScannerT> top;
  78
  79         rule<ScannerT> const&
  80         start() const { return top; }
  81     };
  82 };
  83
  84 ////////////////////////////////////////////////////////////////////////////
  85 //
  86 //  Main program
  87 //
  88 ////////////////////////////////////////////////////////////////////////////
  89 int
  90 main()
  91 {
  92     cout << "/////////////////////////////////////////////////////////\n\n";
  93     cout << "\t\tExpression parser using Phoenix...\n\n";
  94     cout << "/////////////////////////////////////////////////////////\n\n";
  95     cout << "Type an expression...or [q or Q] to quit\n\n";
  96
  97     calculator calc;    //  Our parser
  98
  99     string str;
 100     while (getline(cin, str))
 101     {
 102         if (str.empty() || str[0] == 'q' || str[0] == 'Q')
 103             break;
 104
 105         double n = 0;
 106         parse_info<> info = parse(str.c_str(), calc[var(n) = arg1], space_p);
 107
 108         //  calc[var(n) = arg1] invokes the calculator and extracts
 109         //  the result of the computation. See calculator grammar
 110         //  note above.
 111
 112         if (info.full)
 113         {
 114             cout << "-------------------------\n";
 115             cout << "Parsing succeeded\n";
 116             cout << "result = " << n << endl;
 117             cout << "-------------------------\n";
 118         }
 119         else
 120         {
 121             cout << "-------------------------\n";
 122             cout << "Parsing failed\n";
 123             cout << "stopped at: \": " << info.stop << "\"\n";
 124             cout << "-------------------------\n";
 125         }
 126     }
 127
 128     cout << "Bye... :-) \n\n";
 129     return 0;
 130 }
 131
 132