| /*============================================================================= |
| Copyright (c) 2001-2010 Joel de Guzman |
| |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
| =============================================================================*/ |
| /////////////////////////////////////////////////////////////////////////////// |
| // |
| // This time, we'll incorporate error handling and reporting. |
| // |
| // [ JDG June 29, 2002 ] spirit1 |
| // [ JDG March 5, 2007 ] spirit2 |
| // |
| /////////////////////////////////////////////////////////////////////////////// |
| |
| #include <boost/config/warning_disable.hpp> |
| #include <boost/spirit/include/qi.hpp> |
| #include <boost/spirit/include/phoenix_operator.hpp> |
| #include <boost/spirit/include/phoenix_object.hpp> |
| |
| #include <iostream> |
| #include <string> |
| |
| namespace client |
| { |
| namespace qi = boost::spirit::qi; |
| namespace phoenix = boost::phoenix; |
| namespace ascii = boost::spirit::ascii; |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // Our calculator grammar |
| /////////////////////////////////////////////////////////////////////////////// |
| template <typename Iterator> |
| struct calculator : qi::grammar<Iterator, int(), ascii::space_type> |
| { |
| calculator() : calculator::base_type(expression) |
| { |
| using namespace qi::labels; |
| using qi::uint_; |
| using qi::on_error; |
| using qi::fail; |
| |
| using phoenix::construct; |
| using phoenix::val; |
| |
| expression = |
| term [_val = _1] |
| >> *( ('+' > term [_val += _1]) |
| | ('-' > term [_val -= _1]) |
| ) |
| ; |
| |
| term = |
| factor [_val = _1] |
| >> *( ('*' > factor [_val *= _1]) |
| | ('/' > factor [_val /= _1]) |
| ) |
| ; |
| |
| factor = |
| uint_ [_val = _1] |
| | '(' > expression [_val = _1] > ')' |
| | ('-' > factor [_val = -_1]) |
| | ('+' > factor [_val = _1]) |
| ; |
| |
| expression.name("expression"); |
| term.name("term"); |
| factor.name("factor"); |
| |
| on_error<fail> |
| ( |
| expression |
| , std::cout |
| << val("Error! Expecting ") |
| << _4 // what failed? |
| << val(" here: \"") |
| << construct<std::string>(_3, _2) // iterators to error-pos, end |
| << val("\"") |
| << std::endl |
| ); |
| } |
| |
| qi::rule<Iterator, int(), ascii::space_type> expression, term, factor; |
| }; |
| } |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // Main program |
| /////////////////////////////////////////////////////////////////////////////// |
| int |
| main() |
| { |
| std::cout << "/////////////////////////////////////////////////////////\n\n"; |
| std::cout << "Expression parser...\n\n"; |
| std::cout << "/////////////////////////////////////////////////////////\n\n"; |
| std::cout << "Type an expression...or [q or Q] to quit\n\n"; |
| |
| using boost::spirit::ascii::space; |
| typedef std::string::const_iterator iterator_type; |
| typedef client::calculator<iterator_type> calculator; |
| |
| calculator calc; // Our grammar |
| |
| std::string str; |
| int result; |
| while (std::getline(std::cin, str)) |
| { |
| if (str.empty() || str[0] == 'q' || str[0] == 'Q') |
| break; |
| |
| std::string::const_iterator iter = str.begin(); |
| std::string::const_iterator end = str.end(); |
| bool r = phrase_parse(iter, end, calc, space, result); |
| |
| if (r && iter == end) |
| { |
| std::cout << "-------------------------\n"; |
| std::cout << "Parsing succeeded\n"; |
| std::cout << "result = " << result << std::endl; |
| std::cout << "-------------------------\n"; |
| } |
| else |
| { |
| std::cout << "-------------------------\n"; |
| std::cout << "Parsing failed\n"; |
| std::cout << "-------------------------\n"; |
| } |
| } |
| |
| std::cout << "Bye... :-) \n\n"; |
| return 0; |
| } |
| |
| |