/*============================================================================= 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) =============================================================================*/ /////////////////////////////////////////////////////////////////////////////// // // A Roman Numerals Parser (demonstrating the symbol table). This is // discussed in the "Symbols" chapter in the Spirit User's Guide. // // [ JDG August 22, 2002 ] spirit1 // [ JDG March 13, 2007 ] spirit2 // /////////////////////////////////////////////////////////////////////////////// #include #include #include #include #include namespace client { namespace qi = boost::spirit::qi; namespace ascii = boost::spirit::ascii; /////////////////////////////////////////////////////////////////////////////// // Parse roman hundreds (100..900) numerals using the symbol table. // Notice that the data associated with each slot is the parser's attribute // (which is passed to attached semantic actions). /////////////////////////////////////////////////////////////////////////////// //[tutorial_roman_hundreds struct hundreds_ : qi::symbols { hundreds_() { add ("C" , 100) ("CC" , 200) ("CCC" , 300) ("CD" , 400) ("D" , 500) ("DC" , 600) ("DCC" , 700) ("DCCC" , 800) ("CM" , 900) ; } } hundreds; //] /////////////////////////////////////////////////////////////////////////////// // Parse roman tens (10..90) numerals using the symbol table. /////////////////////////////////////////////////////////////////////////////// //[tutorial_roman_tens struct tens_ : qi::symbols { tens_() { add ("X" , 10) ("XX" , 20) ("XXX" , 30) ("XL" , 40) ("L" , 50) ("LX" , 60) ("LXX" , 70) ("LXXX" , 80) ("XC" , 90) ; } } tens; //] /////////////////////////////////////////////////////////////////////////////// // Parse roman ones (1..9) numerals using the symbol table. /////////////////////////////////////////////////////////////////////////////// //[tutorial_roman_ones struct ones_ : qi::symbols { ones_() { add ("I" , 1) ("II" , 2) ("III" , 3) ("IV" , 4) ("V" , 5) ("VI" , 6) ("VII" , 7) ("VIII" , 8) ("IX" , 9) ; } } ones; //] /////////////////////////////////////////////////////////////////////////////// // roman (numerals) grammar // // Note the use of the || operator. The expression // a || b reads match a or b and in sequence. Try // defining the roman numerals grammar in YACC or // PCCTS. Spirit rules! :-) /////////////////////////////////////////////////////////////////////////////// //[tutorial_roman_grammar template struct roman : qi::grammar { roman() : roman::base_type(start) { using qi::eps; using qi::lit; using qi::_val; using qi::_1; using ascii::char_; start = eps [_val = 0] >> ( +lit('M') [_val += 1000] || hundreds [_val += _1] || tens [_val += _1] || ones [_val += _1] ) ; } qi::rule start; }; //] } /////////////////////////////////////////////////////////////////////////////// // Main program /////////////////////////////////////////////////////////////////////////////// int main() { std::cout << "/////////////////////////////////////////////////////////\n\n"; std::cout << "\t\tRoman Numerals Parser\n\n"; std::cout << "/////////////////////////////////////////////////////////\n\n"; std::cout << "Type a Roman Numeral ...or [q or Q] to quit\n\n"; typedef std::string::const_iterator iterator_type; typedef client::roman roman; roman roman_parser; // Our grammar std::string str; unsigned 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(); //[tutorial_roman_grammar_parse bool r = parse(iter, end, roman_parser, result); if (r && iter == end) { std::cout << "-------------------------\n"; std::cout << "Parsing succeeded\n"; std::cout << "result = " << result << std::endl; std::cout << "-------------------------\n"; } else { std::string rest(iter, end); std::cout << "-------------------------\n"; std::cout << "Parsing failed\n"; std::cout << "stopped at: \": " << rest << "\"\n"; std::cout << "-------------------------\n"; } //] } std::cout << "Bye... :-) \n\n"; return 0; }