125 lines
4.3 KiB
C++
125 lines
4.3 KiB
C++
/*=============================================================================
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Copyright (c) 2001-2011 Joel de Guzman
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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///////////////////////////////////////////////////////////////////////////////
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//
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// A calculator example demonstrating the grammar and semantic actions
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// using phoenix to do the actual expression evaluation. The parser is
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// essentially an "interpreter" that evaluates expressions on the fly.
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//
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// [ JDG June 29, 2002 ] spirit1
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// [ JDG March 5, 2007 ] spirit2
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//
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///////////////////////////////////////////////////////////////////////////////
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// Spirit v2.5 allows you to suppress automatic generation
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// of predefined terminals to speed up complation. With
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// BOOST_SPIRIT_NO_PREDEFINED_TERMINALS defined, you are
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// responsible in creating instances of the terminals that
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// you need (e.g. see qi::uint_type uint_ below).
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#define BOOST_SPIRIT_NO_PREDEFINED_TERMINALS
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#include <boost/config/warning_disable.hpp>
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#include <boost/spirit/include/qi.hpp>
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#include <boost/spirit/include/phoenix_operator.hpp>
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#include <iostream>
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#include <string>
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namespace client
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{
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namespace qi = boost::spirit::qi;
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namespace ascii = boost::spirit::ascii;
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///////////////////////////////////////////////////////////////////////////
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// Our calculator grammar
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///////////////////////////////////////////////////////////////////////////
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template <typename Iterator>
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struct calculator : qi::grammar<Iterator, int(), ascii::space_type>
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{
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calculator() : calculator::base_type(expression)
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{
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qi::_val_type _val;
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qi::_1_type _1;
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qi::uint_type uint_;
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expression =
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term [_val = _1]
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>> *( ('+' >> term [_val += _1])
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| ('-' >> term [_val -= _1])
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)
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;
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term =
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factor [_val = _1]
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>> *( ('*' >> factor [_val *= _1])
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| ('/' >> factor [_val /= _1])
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)
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;
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factor =
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uint_ [_val = _1]
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| '(' >> expression [_val = _1] >> ')'
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| ('-' >> factor [_val = -_1])
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| ('+' >> factor [_val = _1])
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;
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}
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qi::rule<Iterator, int(), ascii::space_type> expression, term, factor;
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};
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}
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///////////////////////////////////////////////////////////////////////////////
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// Main program
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///////////////////////////////////////////////////////////////////////////////
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int
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main()
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{
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std::cout << "/////////////////////////////////////////////////////////\n\n";
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std::cout << "Expression parser...\n\n";
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std::cout << "/////////////////////////////////////////////////////////\n\n";
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std::cout << "Type an expression...or [q or Q] to quit\n\n";
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typedef std::string::const_iterator iterator_type;
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typedef client::calculator<iterator_type> calculator;
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boost::spirit::ascii::space_type space; // Our skipper
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calculator calc; // Our grammar
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std::string str;
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int result;
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while (std::getline(std::cin, str))
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{
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if (str.empty() || str[0] == 'q' || str[0] == 'Q')
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break;
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std::string::const_iterator iter = str.begin();
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std::string::const_iterator end = str.end();
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bool r = phrase_parse(iter, end, calc, space, result);
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if (r && iter == end)
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{
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std::cout << "-------------------------\n";
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std::cout << "Parsing succeeded\n";
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std::cout << "result = " << result << std::endl;
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std::cout << "-------------------------\n";
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}
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else
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{
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std::string rest(iter, end);
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std::cout << "-------------------------\n";
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std::cout << "Parsing failed\n";
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std::cout << "stopped at: \" " << rest << "\"\n";
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std::cout << "-------------------------\n";
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}
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}
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std::cout << "Bye... :-) \n\n";
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return 0;
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}
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