| /*============================================================================= |
| Copyright (c) 2002-2003 Joel de Guzman |
| http://spirit.sourceforge.net/ |
| |
| Use, modification and distribution is subject to 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) |
| =============================================================================*/ |
| //////////////////////////////////////////////////////////////////////////// |
| // |
| // Full calculator example demonstrating Phoenix |
| // This is discussed in the "Closures" chapter in the Spirit User's Guide. |
| // |
| // [ JDG 6/29/2002 ] |
| // |
| //////////////////////////////////////////////////////////////////////////// |
| #include <boost/spirit/include/classic_core.hpp> |
| #include <boost/spirit/include/classic_attribute.hpp> |
| #include <iostream> |
| #include <string> |
| |
| //////////////////////////////////////////////////////////////////////////// |
| using namespace std; |
| using namespace BOOST_SPIRIT_CLASSIC_NS; |
| using namespace phoenix; |
| |
| //////////////////////////////////////////////////////////////////////////// |
| // |
| // Our calculator grammar using phoenix to do the semantics |
| // |
| // Note: The top rule propagates the expression result (value) upwards |
| // to the calculator grammar self.val closure member which is |
| // then visible outside the grammar (i.e. since self.val is the |
| // member1 of the closure, it becomes the attribute passed by |
| // the calculator to an attached semantic action. See the |
| // driver code that uses the calculator below). |
| // |
| //////////////////////////////////////////////////////////////////////////// |
| struct calc_closure : BOOST_SPIRIT_CLASSIC_NS::closure<calc_closure, double> |
| { |
| member1 val; |
| }; |
| |
| struct calculator : public grammar<calculator, calc_closure::context_t> |
| { |
| template <typename ScannerT> |
| struct definition |
| { |
| definition(calculator const& self) |
| { |
| top = expression[self.val = arg1]; |
| |
| expression |
| = term[expression.val = arg1] |
| >> *( ('+' >> term[expression.val += arg1]) |
| | ('-' >> term[expression.val -= arg1]) |
| ) |
| ; |
| |
| term |
| = factor[term.val = arg1] |
| >> *( ('*' >> factor[term.val *= arg1]) |
| | ('/' >> factor[term.val /= arg1]) |
| ) |
| ; |
| |
| factor |
| = ureal_p[factor.val = arg1] |
| | '(' >> expression[factor.val = arg1] >> ')' |
| | ('-' >> factor[factor.val = -arg1]) |
| | ('+' >> factor[factor.val = arg1]) |
| ; |
| } |
| |
| typedef rule<ScannerT, calc_closure::context_t> rule_t; |
| rule_t expression, term, factor; |
| rule<ScannerT> top; |
| |
| rule<ScannerT> const& |
| start() const { return top; } |
| }; |
| }; |
| |
| //////////////////////////////////////////////////////////////////////////// |
| // |
| // Main program |
| // |
| //////////////////////////////////////////////////////////////////////////// |
| int |
| main() |
| { |
| cout << "/////////////////////////////////////////////////////////\n\n"; |
| cout << "\t\tExpression parser using Phoenix...\n\n"; |
| cout << "/////////////////////////////////////////////////////////\n\n"; |
| cout << "Type an expression...or [q or Q] to quit\n\n"; |
| |
| calculator calc; // Our parser |
| |
| string str; |
| while (getline(cin, str)) |
| { |
| if (str.empty() || str[0] == 'q' || str[0] == 'Q') |
| break; |
| |
| double n = 0; |
| parse_info<> info = parse(str.c_str(), calc[var(n) = arg1], space_p); |
| |
| // calc[var(n) = arg1] invokes the calculator and extracts |
| // the result of the computation. See calculator grammar |
| // note above. |
| |
| if (info.full) |
| { |
| cout << "-------------------------\n"; |
| cout << "Parsing succeeded\n"; |
| cout << "result = " << n << endl; |
| cout << "-------------------------\n"; |
| } |
| else |
| { |
| cout << "-------------------------\n"; |
| cout << "Parsing failed\n"; |
| cout << "stopped at: \": " << info.stop << "\"\n"; |
| cout << "-------------------------\n"; |
| } |
| } |
| |
| cout << "Bye... :-) \n\n"; |
| return 0; |
| } |
| |
| |