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- /*=============================================================================
- Copyright (c) 2001-2015 Joel de Guzman
- Copyright (c) 2015 Ahmed Charles
- 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
- // [ JDG May 13, 2015 ] spirit X3
- //
- ///////////////////////////////////////////////////////////////////////////////
- #include <boost/config/warning_disable.hpp>
- #include <boost/spirit/home/x3.hpp>
- #include <iostream>
- #include <string>
- namespace client
- {
- namespace x3 = boost::spirit::x3;
- namespace ascii = boost::spirit::x3::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).
- ///////////////////////////////////////////////////////////////////////////////
- struct hundreds_ : x3::symbols<unsigned>
- {
- 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.
- ///////////////////////////////////////////////////////////////////////////////
- struct tens_ : x3::symbols<unsigned>
- {
- 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.
- ///////////////////////////////////////////////////////////////////////////////
- struct ones_ : x3::symbols<unsigned>
- {
- 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! :-)
- ///////////////////////////////////////////////////////////////////////////////
- namespace parser
- {
- using x3::eps;
- using x3::lit;
- using x3::_val;
- using x3::_attr;
- using ascii::char_;
- auto set_zero = [](auto& ctx){ _val(ctx) = 0; };
- auto add1000 = [](auto& ctx){ _val(ctx) += 1000; };
- auto add = [](auto& ctx){ _val(ctx) += _attr(ctx); };
- x3::rule<class roman, unsigned> const roman = "roman";
- auto const roman_def =
- eps [set_zero]
- >>
- (
- -(+lit('M') [add1000])
- >> -hundreds [add]
- >> -tens [add]
- >> -ones [add]
- )
- ;
- BOOST_SPIRIT_DEFINE(roman);
- }
- }
- ///////////////////////////////////////////////////////////////////////////////
- // 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;
- using client::parser::roman; // Our parser
- std::string str;
- unsigned result;
- while (std::getline(std::cin, str))
- {
- if (str.empty() || str[0] == 'q' || str[0] == 'Q')
- break;
- iterator_type iter = str.begin();
- iterator_type const end = str.end();
- bool r = parse(iter, end, roman, 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;
- }
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