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- /*=============================================================================
- Copyright (c) 2002-2003 Hartmut Kaiser
- 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 and subrules ]
- //
- // [ Hartmut Kaiser 10/8/2002 ]
- //
- ///////////////////////////////////////////////////////////////////////////////
- //#define BOOST_SPIRIT_DEBUG // define this for debug output
- #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 and subrule's
- // as it's working horses
- //
- // 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 =
- term[self.val = arg1]
- >> *( ('+' >> term[self.val += arg1])
- | ('-' >> term[self.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])
- );
- BOOST_SPIRIT_DEBUG_NODE(top);
- BOOST_SPIRIT_DEBUG_NODE(expression);
- BOOST_SPIRIT_DEBUG_NODE(term);
- BOOST_SPIRIT_DEBUG_NODE(factor);
- }
- subrule<0, calc_closure::context_t> expression;
- subrule<1, calc_closure::context_t> term;
- subrule<2, calc_closure::context_t> 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;
- }
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