133 lines
4.3 KiB
C++
133 lines
4.3 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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// Full calculator example demonstrating Phoenix
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// This is discussed in the "Closures" chapter in the Spirit User's Guide.
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//
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// [ JDG 6/29/2002 ]
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//
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////////////////////////////////////////////////////////////////////////////
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#include <boost/spirit/include/classic_core.hpp>
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#include <boost/spirit/include/classic_attribute.hpp>
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#include <iostream>
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#include <string>
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////////////////////////////////////////////////////////////////////////////
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using namespace std;
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using namespace BOOST_SPIRIT_CLASSIC_NS;
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using namespace phoenix;
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////////////////////////////////////////////////////////////////////////////
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//
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// Our calculator grammar using phoenix to do the semantics
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//
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// Note: The top rule propagates the expression result (value) upwards
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// to the calculator grammar self.val closure member which is
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// then visible outside the grammar (i.e. since self.val is the
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// member1 of the closure, it becomes the attribute passed by
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// the calculator to an attached semantic action. See the
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// driver code that uses the calculator below).
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//
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////////////////////////////////////////////////////////////////////////////
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struct calc_closure : BOOST_SPIRIT_CLASSIC_NS::closure<calc_closure, double>
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{
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member1 val;
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};
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struct calculator : public grammar<calculator, calc_closure::context_t>
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{
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template <typename ScannerT>
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struct definition
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{
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definition(calculator const& self)
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{
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top = expression[self.val = arg1];
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expression
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= term[expression.val = arg1]
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>> *( ('+' >> term[expression.val += arg1])
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| ('-' >> term[expression.val -= arg1])
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)
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;
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term
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= factor[term.val = arg1]
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>> *( ('*' >> factor[term.val *= arg1])
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| ('/' >> factor[term.val /= arg1])
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)
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;
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factor
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= ureal_p[factor.val = arg1]
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| '(' >> expression[factor.val = arg1] >> ')'
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| ('-' >> factor[factor.val = -arg1])
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| ('+' >> factor[factor.val = arg1])
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;
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}
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typedef rule<ScannerT, calc_closure::context_t> rule_t;
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rule_t expression, term, factor;
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rule<ScannerT> top;
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rule<ScannerT> const&
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start() const { return top; }
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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\tExpression parser using Phoenix...\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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double n = 0;
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parse_info<> info = parse(str.c_str(), calc[var(n) = arg1], space_p);
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// calc[var(n) = arg1] invokes the calculator and extracts
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// the result of the computation. See calculator grammar
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// note above.
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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 << "result = " << n << endl;
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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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