1 /*=============================================================================
2 Copyright (c) 2001-2011 Hartmut Kaiser
3 Copyright (c) 2001-2011 Joel de Guzman
4
5 Distributed under the Boost Software License, Version 1.0. (See accompanying
6 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7 =============================================================================*/
8 ///////////////////////////////////////////////////////////////////////////////
9 //
10 // Plain calculator example demonstrating the grammar. The parser is a
11 // syntax checker only and does not do any semantic evaluation.
12 //
13 // [ JDG May 10, 2002 ] spirit1
14 // [ JDG March 4, 2007 ] spirit2
15 // [ HK November 30, 2010 ] spirit2/utree
16 //
17 ///////////////////////////////////////////////////////////////////////////////
18
19 // This rather naive example demonstrates that you can pass an instance of a
20 // utree as the attribute for almost any grammar. As the result the utree will
21 // be filled with the parse tree as generated during the parsing. This is most
22 // of the time not what's desired, but is usually a good first step in order to
23 // prepare your grammar to generate a customized AST. See the calc_utree_ast
24 // example for a modified version of this grammar filling the attribute with a
25 // AST (abstract syntax tree) representing the math expression as matched from
26 // the input.
27
28 // #define BOOST_SPIRIT_DEBUG
29
30 #include <boost/config/warning_disable.hpp>
31 #include <boost/spirit/include/qi.hpp>
32 #include <boost/spirit/include/support_utree.hpp>
33
34 #include <iostream>
35 #include <string>
36
37 namespace client
38 {
39 namespace qi = boost::spirit::qi;
40 namespace ascii = boost::spirit::ascii;
41 namespace spirit = boost::spirit;
42
43 ///////////////////////////////////////////////////////////////////////////////
44 // Our calculator grammar
45 ///////////////////////////////////////////////////////////////////////////////
46 template <typename Iterator>
47 struct calculator : qi::grammar<Iterator, ascii::space_type, spirit::utree()>
48 {
calculatorclient::calculator49 calculator() : calculator::base_type(expression)
50 {
51 using qi::uint_;
52 using qi::char_;
53
54 expression =
55 term
56 >> *( (char_('+') >> term)
57 | (char_('-') >> term)
58 )
59 ;
60
61 term =
62 factor
63 >> *( (char_('*') >> factor)
64 | (char_('/') >> factor)
65 )
66 ;
67
68 factor =
69 uint_
70 | '(' >> expression >> ')'
71 | (char_('-') >> factor)
72 | (char_('+') >> factor)
73 ;
74
75 BOOST_SPIRIT_DEBUG_NODE(expression);
76 BOOST_SPIRIT_DEBUG_NODE(term);
77 BOOST_SPIRIT_DEBUG_NODE(factor);
78 }
79
80 qi::rule<Iterator, ascii::space_type, spirit::utree()> expression;
81 qi::rule<Iterator, ascii::space_type, spirit::utree::list_type()> term;
82 qi::rule<Iterator, ascii::space_type, spirit::utree::list_type()> factor;
83 };
84 }
85
86 ///////////////////////////////////////////////////////////////////////////////
87 // Main program
88 ///////////////////////////////////////////////////////////////////////////////
main()89 int main()
90 {
91 std::cout << "/////////////////////////////////////////////////////////\n\n";
92 std::cout << "Expression parser...\n\n";
93 std::cout << "/////////////////////////////////////////////////////////\n\n";
94 std::cout << "Type an expression...or [q or Q] to quit\n\n";
95
96 using boost::spirit::ascii::space;
97 using boost::spirit::utree;
98 typedef std::string::const_iterator iterator_type;
99 typedef client::calculator<iterator_type> calculator;
100
101 calculator calc; // Our grammar
102
103 std::string str;
104 while (std::getline(std::cin, str))
105 {
106 if (str.empty() || str[0] == 'q' || str[0] == 'Q')
107 break;
108
109 std::string::const_iterator iter = str.begin();
110 std::string::const_iterator end = str.end();
111 utree ut;
112 bool r = phrase_parse(iter, end, calc, space, ut);
113
114 if (r && iter == end)
115 {
116 std::cout << "-------------------------\n";
117 std::cout << "Parsing succeeded: " << ut << "\n";
118 std::cout << "-------------------------\n";
119 }
120 else
121 {
122 std::string rest(iter, end);
123 std::cout << "-------------------------\n";
124 std::cout << "Parsing failed\n";
125 std::cout << "stopped at: \": " << rest << "\"\n";
126 std::cout << "-------------------------\n";
127 }
128 }
129
130 std::cout << "Bye... :-) \n\n";
131 return 0;
132 }
133
134
135