135 lines
4.6 KiB
C++
135 lines
4.6 KiB
C++
/*=============================================================================
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Copyright (c) 2001-2011 Hartmut Kaiser
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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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// Plain calculator example demonstrating the grammar. The parser is a
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// syntax checker only and does not do any semantic evaluation.
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//
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// [ JDG May 10, 2002 ] spirit1
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// [ JDG March 4, 2007 ] spirit2
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// [ HK November 30, 2010 ] spirit2/utree
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//
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///////////////////////////////////////////////////////////////////////////////
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// This rather naive example demonstrates that you can pass an instance of a
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// utree as the attribute for almost any grammar. As the result the utree will
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// be filled with the parse tree as generated during the parsing. This is most
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// of the time not what's desired, but is usually a good first step in order to
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// prepare your grammar to generate a customized AST. See the calc_utree_ast
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// example for a modified version of this grammar filling the attribute with a
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// AST (abstract syntax tree) representing the math expression as matched from
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// the input.
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// #define BOOST_SPIRIT_DEBUG
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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/support_utree.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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namespace spirit = boost::spirit;
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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, ascii::space_type, spirit::utree()>
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{
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calculator() : calculator::base_type(expression)
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{
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using qi::uint_;
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using qi::char_;
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expression =
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term
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>> *( (char_('+') >> term)
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| (char_('-') >> term)
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)
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;
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term =
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factor
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>> *( (char_('*') >> factor)
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| (char_('/') >> factor)
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)
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;
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factor =
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uint_
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| '(' >> expression >> ')'
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| (char_('-') >> factor)
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| (char_('+') >> factor)
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;
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BOOST_SPIRIT_DEBUG_NODE(expression);
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BOOST_SPIRIT_DEBUG_NODE(term);
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BOOST_SPIRIT_DEBUG_NODE(factor);
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}
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qi::rule<Iterator, ascii::space_type, spirit::utree()> expression;
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qi::rule<Iterator, ascii::space_type, spirit::utree::list_type()> term;
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qi::rule<Iterator, ascii::space_type, spirit::utree::list_type()> 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 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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using boost::spirit::ascii::space;
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using boost::spirit::utree;
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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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calculator calc; // Our grammar
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std::string str;
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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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utree ut;
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bool r = phrase_parse(iter, end, calc, space, ut);
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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: " << ut << "\n";
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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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