| /*============================================================================= |
| Copyright (c) 2001-2011 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 Calculator example demonstrating generation of AST. The AST, |
| // once created, is traversed, 1) To print its contents and |
| // 2) To evaluate the result. |
| // |
| // [ JDG April 28, 2008 ] For BoostCon 2008 |
| // [ JDG February 18, 2011 ] Pure attributes. No semantic actions. |
| // |
| /////////////////////////////////////////////////////////////////////////////// |
| |
| // Spirit v2.5 allows you to suppress automatic generation |
| // of predefined terminals to speed up complation. With |
| // BOOST_SPIRIT_NO_PREDEFINED_TERMINALS defined, you are |
| // responsible in creating instances of the terminals that |
| // you need (e.g. see qi::uint_type uint_ below). |
| #define BOOST_SPIRIT_NO_PREDEFINED_TERMINALS |
| |
| #if defined(_MSC_VER) |
| # pragma warning(disable: 4345) |
| #endif |
| |
| #include <boost/config/warning_disable.hpp> |
| #include <boost/spirit/include/qi.hpp> |
| #include <boost/variant/recursive_variant.hpp> |
| #include <boost/variant/apply_visitor.hpp> |
| #include <boost/fusion/include/adapt_struct.hpp> |
| #include <boost/foreach.hpp> |
| |
| #include <iostream> |
| #include <string> |
| |
| namespace client { namespace ast |
| { |
| /////////////////////////////////////////////////////////////////////////// |
| // The AST |
| /////////////////////////////////////////////////////////////////////////// |
| struct nil {}; |
| struct signed_; |
| struct program; |
| |
| typedef boost::variant< |
| nil |
| , unsigned int |
| , boost::recursive_wrapper<signed_> |
| , boost::recursive_wrapper<program> |
| > |
| operand; |
| |
| struct signed_ |
| { |
| char sign; |
| operand operand_; |
| }; |
| |
| struct operation |
| { |
| char operator_; |
| operand operand_; |
| }; |
| |
| struct program |
| { |
| operand first; |
| std::list<operation> rest; |
| }; |
| }} |
| |
| BOOST_FUSION_ADAPT_STRUCT( |
| client::ast::signed_, |
| (char, sign) |
| (client::ast::operand, operand_) |
| ) |
| |
| BOOST_FUSION_ADAPT_STRUCT( |
| client::ast::operation, |
| (char, operator_) |
| (client::ast::operand, operand_) |
| ) |
| |
| BOOST_FUSION_ADAPT_STRUCT( |
| client::ast::program, |
| (client::ast::operand, first) |
| (std::list<client::ast::operation>, rest) |
| ) |
| |
| namespace client { namespace ast |
| { |
| /////////////////////////////////////////////////////////////////////////// |
| // The AST Printer |
| /////////////////////////////////////////////////////////////////////////// |
| struct printer |
| { |
| typedef void result_type; |
| |
| void operator()(nil) const {} |
| void operator()(unsigned int n) const { std::cout << n; } |
| |
| void operator()(operation const& x) const |
| { |
| boost::apply_visitor(*this, x.operand_); |
| switch (x.operator_) |
| { |
| case '+': std::cout << " add"; break; |
| case '-': std::cout << " subt"; break; |
| case '*': std::cout << " mult"; break; |
| case '/': std::cout << " div"; break; |
| } |
| } |
| |
| void operator()(signed_ const& x) const |
| { |
| boost::apply_visitor(*this, x.operand_); |
| switch (x.sign) |
| { |
| case '-': std::cout << " neg"; break; |
| case '+': std::cout << " pos"; break; |
| } |
| } |
| |
| void operator()(program const& x) const |
| { |
| boost::apply_visitor(*this, x.first); |
| BOOST_FOREACH(operation const& oper, x.rest) |
| { |
| std::cout << ' '; |
| (*this)(oper); |
| } |
| } |
| }; |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // The AST evaluator |
| /////////////////////////////////////////////////////////////////////////// |
| struct eval |
| { |
| typedef int result_type; |
| |
| int operator()(nil) const { BOOST_ASSERT(0); return 0; } |
| int operator()(unsigned int n) const { return n; } |
| |
| int operator()(operation const& x, int lhs) const |
| { |
| int rhs = boost::apply_visitor(*this, x.operand_); |
| switch (x.operator_) |
| { |
| case '+': return lhs + rhs; |
| case '-': return lhs - rhs; |
| case '*': return lhs * rhs; |
| case '/': return lhs / rhs; |
| } |
| BOOST_ASSERT(0); |
| return 0; |
| } |
| |
| int operator()(signed_ const& x) const |
| { |
| int rhs = boost::apply_visitor(*this, x.operand_); |
| switch (x.sign) |
| { |
| case '-': return -rhs; |
| case '+': return +rhs; |
| } |
| BOOST_ASSERT(0); |
| return 0; |
| } |
| |
| int operator()(program const& x) const |
| { |
| int state = boost::apply_visitor(*this, x.first); |
| BOOST_FOREACH(operation const& oper, x.rest) |
| { |
| state = (*this)(oper, state); |
| } |
| return state; |
| } |
| }; |
| }} |
| |
| namespace client |
| { |
| namespace qi = boost::spirit::qi; |
| namespace ascii = boost::spirit::ascii; |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // The calculator grammar |
| /////////////////////////////////////////////////////////////////////////////// |
| template <typename Iterator> |
| struct calculator : qi::grammar<Iterator, ast::program(), ascii::space_type> |
| { |
| calculator() : calculator::base_type(expression) |
| { |
| qi::uint_type uint_; |
| qi::char_type char_; |
| |
| expression = |
| term |
| >> *( (char_('+') >> term) |
| | (char_('-') >> term) |
| ) |
| ; |
| |
| term = |
| factor |
| >> *( (char_('*') >> factor) |
| | (char_('/') >> factor) |
| ) |
| ; |
| |
| factor = |
| uint_ |
| | '(' >> expression >> ')' |
| | (char_('-') >> factor) |
| | (char_('+') >> factor) |
| ; |
| } |
| |
| qi::rule<Iterator, ast::program(), ascii::space_type> expression; |
| qi::rule<Iterator, ast::program(), ascii::space_type> term; |
| qi::rule<Iterator, ast::operand(), ascii::space_type> 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"; |
| |
| typedef std::string::const_iterator iterator_type; |
| typedef client::calculator<iterator_type> calculator; |
| typedef client::ast::program ast_program; |
| typedef client::ast::printer ast_print; |
| typedef client::ast::eval ast_eval; |
| |
| std::string str; |
| while (std::getline(std::cin, str)) |
| { |
| if (str.empty() || str[0] == 'q' || str[0] == 'Q') |
| break; |
| |
| calculator calc; // Our grammar |
| ast_program program; // Our program (AST) |
| ast_print print; // Prints the program |
| ast_eval eval; // Evaluates the program |
| |
| std::string::const_iterator iter = str.begin(); |
| std::string::const_iterator end = str.end(); |
| boost::spirit::ascii::space_type space; |
| bool r = phrase_parse(iter, end, calc, space, program); |
| |
| if (r && iter == end) |
| { |
| std::cout << "-------------------------\n"; |
| std::cout << "Parsing succeeded\n"; |
| print(program); |
| std::cout << "\nResult: " << eval(program) << 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; |
| } |
| |
| |