141 lines
4.2 KiB
C++
141 lines
4.2 KiB
C++
/*=============================================================================
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Copyright (c) 2002-2003 Joel de Guzman
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http://spirit.sourceforge.net/
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Use, modification and distribution is subject to the Boost Software
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License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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///////////////////////////////////////////////////////////////////////////////
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//
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// This calculator example demontrates the use of subrules.
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// This is discussed in the "Subrule" chapter in the Spirit User's Guide.
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//
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// [ JDG 4/11/2002 ]
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//
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///////////////////////////////////////////////////////////////////////////////
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//#define BOOST_SPIRIT_DEBUG // define this for debug output
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#include <boost/spirit/include/classic_core.hpp>
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#include <iostream>
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#include <string>
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using namespace std;
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using namespace BOOST_SPIRIT_CLASSIC_NS;
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///////////////////////////////////////////////////////////////////////////////
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//
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// Semantic actions
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//
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///////////////////////////////////////////////////////////////////////////////
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namespace
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{
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void do_int(char const* str, char const* end)
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{
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string s(str, end);
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cout << "PUSH(" << s << ')' << endl;
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}
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void do_add(char const*, char const*) { cout << "ADD\n"; }
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void do_subt(char const*, char const*) { cout << "SUBTRACT\n"; }
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void do_mult(char const*, char const*) { cout << "MULTIPLY\n"; }
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void do_div(char const*, char const*) { cout << "DIVIDE\n"; }
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void do_neg(char const*, char const*) { cout << "NEGATE\n"; }
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}
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///////////////////////////////////////////////////////////////////////////////
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//
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// Our calculator grammar (using subrules)
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//
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///////////////////////////////////////////////////////////////////////////////
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struct calculator : public grammar<calculator>
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{
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template <typename ScannerT>
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struct definition {
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definition(calculator const& /*self*/)
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{
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first = (
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expression =
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term
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>> *( ('+' >> term)[&do_add]
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| ('-' >> term)[&do_subt]
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)
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,
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term =
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factor
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>> *( ('*' >> factor)[&do_mult]
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| ('/' >> factor)[&do_div]
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)
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,
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factor
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= lexeme_d[(+digit_p)[&do_int]]
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| '(' >> expression >> ')'
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| ('-' >> factor)[&do_neg]
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| ('+' >> factor)
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);
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BOOST_SPIRIT_DEBUG_NODE(first);
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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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subrule<0> expression;
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subrule<1> term;
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subrule<2> factor;
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rule<ScannerT> first;
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rule<ScannerT> const&
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start() const { return first; }
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};
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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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///////////////////////////////////////////////////////////////////////////////
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int
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main()
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{
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cout << "/////////////////////////////////////////////////////////\n\n";
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cout << "\t\tA calculator using subrules...\n\n";
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cout << "/////////////////////////////////////////////////////////\n\n";
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cout << "Type an expression...or [q or Q] to quit\n\n";
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calculator calc; // Our parser
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string str;
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while (getline(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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parse_info<> info = parse(str.c_str(), calc, space_p);
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if (info.full)
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{
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cout << "-------------------------\n";
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cout << "Parsing succeeded\n";
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cout << "-------------------------\n";
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}
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else
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{
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cout << "-------------------------\n";
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cout << "Parsing failed\n";
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cout << "stopped at: \": " << info.stop << "\"\n";
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cout << "-------------------------\n";
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}
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}
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cout << "Bye... :-) \n\n";
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return 0;
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}
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