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- /*=============================================================================
- Copyright (c) 2001-2014 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)
- =============================================================================*/
- ///////////////////////////////////////////////////////////////////////////////
- //
- // Same as Calc4, this time, we'll incorporate debugging support,
- // plus error handling and reporting.
- //
- // [ JDG April 28, 2008 ] For BoostCon 2008
- // [ JDG February 18, 2011 ] Pure attributes. No semantic actions.
- // [ JDG April 9, 2014 ] Spirit X3
- //
- ///////////////////////////////////////////////////////////////////////////////
- ///////////////////////////////////////////////////////////////////////////////
- // Uncomment this if you want to enable debugging
- //#define BOOST_SPIRIT_X3_DEBUG
- #include <boost/config/warning_disable.hpp>
- #include <boost/spirit/home/x3.hpp>
- #include <boost/spirit/home/x3/support/ast/variant.hpp>
- #include <boost/fusion/include/adapt_struct.hpp>
- #include <iostream>
- #include <string>
- #include <list>
- #include <numeric>
- namespace x3 = boost::spirit::x3;
- namespace client { namespace ast
- {
- ///////////////////////////////////////////////////////////////////////////
- // The AST
- ///////////////////////////////////////////////////////////////////////////
- struct nil {};
- struct signed_;
- struct program;
- struct operand : x3::variant<
- nil
- , unsigned int
- , x3::forward_ast<signed_>
- , x3::forward_ast<program>
- >
- {
- using base_type::base_type;
- using base_type::operator=;
- };
- struct signed_
- {
- char sign;
- operand operand_;
- };
- struct operation
- {
- char operator_;
- operand operand_;
- };
- struct program
- {
- operand first;
- std::list<operation> rest;
- };
- // print function for debugging
- inline std::ostream& operator<<(std::ostream& out, nil) { out << "nil"; return out; }
- }}
- BOOST_FUSION_ADAPT_STRUCT(client::ast::signed_,
- sign, operand_
- )
- BOOST_FUSION_ADAPT_STRUCT(client::ast::operation,
- operator_, operand_
- )
- BOOST_FUSION_ADAPT_STRUCT(client::ast::program,
- first, 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);
- for (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);
- for (operation const& oper : x.rest)
- {
- state = (*this)(oper, state);
- }
- return state;
- }
- };
- }}
- namespace client
- {
- ///////////////////////////////////////////////////////////////////////////////
- // The calculator grammar
- ///////////////////////////////////////////////////////////////////////////////
- namespace calculator_grammar
- {
- using x3::uint_;
- using x3::char_;
- struct expression_class;
- struct term_class;
- struct factor_class;
- x3::rule<expression_class, ast::program> const expression("expression");
- x3::rule<term_class, ast::program> const term("term");
- x3::rule<factor_class, ast::operand> const factor("factor");
- auto const expression_def =
- term
- >> *( (char_('+') > term)
- | (char_('-') > term)
- )
- ;
- auto const term_def =
- factor
- >> *( (char_('*') > factor)
- | (char_('/') > factor)
- )
- ;
- auto const factor_def =
- uint_
- | '(' > expression > ')'
- | (char_('-') > factor)
- | (char_('+') > factor)
- ;
- BOOST_SPIRIT_DEFINE(
- expression
- , term
- , factor
- );
- struct expression_class
- {
- // Our error handler
- template <typename Iterator, typename Exception, typename Context>
- x3::error_handler_result
- on_error(Iterator&, Iterator const& last, Exception const& x, Context const& context)
- {
- std::cout
- << "Error! Expecting: "
- << x.which()
- << " here: \""
- << std::string(x.where(), last)
- << "\""
- << std::endl
- ;
- return x3::error_handler_result::fail;
- }
- };
- auto calculator = expression;
- }
- using calculator_grammar::calculator;
- }
- ///////////////////////////////////////////////////////////////////////////////
- // 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::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;
- auto& calc = client::calculator; // Our grammar
- ast_program program; // Our program (AST)
- ast_print print; // Prints the program
- ast_eval eval; // Evaluates the program
- iterator_type iter = str.begin();
- iterator_type end = str.end();
- boost::spirit::x3::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::cout << "-------------------------\n";
- std::cout << "Parsing failed\n";
- std::cout << "-------------------------\n";
- }
- }
- std::cout << "Bye... :-) \n\n";
- return 0;
- }
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