1 /*=============================================================================
2 Copyright (c) 2001-2011 Joel de Guzman
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 ///////////////////////////////////////////////////////////////////////////////
8 //
9 // A calculator example demonstrating the grammar and semantic actions
10 // using phoenix to do the actual expression evaluation. The parser is
11 // essentially an "interpreter" that evaluates expressions on the fly.
12 //
13 // [ JDG June 29, 2002 ] spirit1
14 // [ JDG March 5, 2007 ] spirit2
15 //
16 ///////////////////////////////////////////////////////////////////////////////
17
18 // Spirit v2.5 allows you to suppress automatic generation
19 // of predefined terminals to speed up complation. With
20 // BOOST_SPIRIT_NO_PREDEFINED_TERMINALS defined, you are
21 // responsible in creating instances of the terminals that
22 // you need (e.g. see qi::uint_type uint_ below).
23 #define BOOST_SPIRIT_NO_PREDEFINED_TERMINALS
24
25 #include <boost/config/warning_disable.hpp>
26 #include <boost/spirit/include/qi.hpp>
27 #include <boost/spirit/include/phoenix_operator.hpp>
28
29 #include <iostream>
30 #include <string>
31
32 namespace client
33 {
34 namespace qi = boost::spirit::qi;
35 namespace ascii = boost::spirit::ascii;
36
37 ///////////////////////////////////////////////////////////////////////////
38 // Our calculator grammar
39 ///////////////////////////////////////////////////////////////////////////
40 template <typename Iterator>
41 struct calculator : qi::grammar<Iterator, int(), ascii::space_type>
42 {
calculatorclient::calculator43 calculator() : calculator::base_type(expression)
44 {
45 qi::_val_type _val;
46 qi::_1_type _1;
47 qi::uint_type uint_;
48
49 expression =
50 term [_val = _1]
51 >> *( ('+' >> term [_val += _1])
52 | ('-' >> term [_val -= _1])
53 )
54 ;
55
56 term =
57 factor [_val = _1]
58 >> *( ('*' >> factor [_val *= _1])
59 | ('/' >> factor [_val /= _1])
60 )
61 ;
62
63 factor =
64 uint_ [_val = _1]
65 | '(' >> expression [_val = _1] >> ')'
66 | ('-' >> factor [_val = -_1])
67 | ('+' >> factor [_val = _1])
68 ;
69 }
70
71 qi::rule<Iterator, int(), ascii::space_type> expression, term, factor;
72 };
73 }
74
75 ///////////////////////////////////////////////////////////////////////////////
76 // Main program
77 ///////////////////////////////////////////////////////////////////////////////
78 int
main()79 main()
80 {
81 std::cout << "/////////////////////////////////////////////////////////\n\n";
82 std::cout << "Expression parser...\n\n";
83 std::cout << "/////////////////////////////////////////////////////////\n\n";
84 std::cout << "Type an expression...or [q or Q] to quit\n\n";
85
86 typedef std::string::const_iterator iterator_type;
87 typedef client::calculator<iterator_type> calculator;
88
89 boost::spirit::ascii::space_type space; // Our skipper
90 calculator calc; // Our grammar
91
92 std::string str;
93 int result;
94 while (std::getline(std::cin, str))
95 {
96 if (str.empty() || str[0] == 'q' || str[0] == 'Q')
97 break;
98
99 std::string::const_iterator iter = str.begin();
100 std::string::const_iterator end = str.end();
101 bool r = phrase_parse(iter, end, calc, space, result);
102
103 if (r && iter == end)
104 {
105 std::cout << "-------------------------\n";
106 std::cout << "Parsing succeeded\n";
107 std::cout << "result = " << result << std::endl;
108 std::cout << "-------------------------\n";
109 }
110 else
111 {
112 std::string rest(iter, end);
113 std::cout << "-------------------------\n";
114 std::cout << "Parsing failed\n";
115 std::cout << "stopped at: \" " << rest << "\"\n";
116 std::cout << "-------------------------\n";
117 }
118 }
119
120 std::cout << "Bye... :-) \n\n";
121 return 0;
122 }
123
124
125