140 lines
4.5 KiB
C++
140 lines
4.5 KiB
C++
/*=============================================================================
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Copyright (c) 2001-2014 Joel de Guzman
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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///////////////////////////////////////////////////////////////////////////////
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//
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// A Calculator example demonstrating the grammar and semantic actions
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// using lambda functions. The parser prints code suitable for a stack
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// based virtual machine.
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//
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// [ JDG May 10, 2002 ] spirit 1
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// [ JDG March 4, 2007 ] spirit 2
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// [ JDG February 21, 2011 ] spirit 2.5
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// [ JDG June 6, 2014 ] spirit x3 (from qi calc2, but using lambda functions)
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//
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///////////////////////////////////////////////////////////////////////////////
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#include <boost/config/warning_disable.hpp>
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#include <boost/spirit/home/x3.hpp>
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#include <boost/spirit/home/x3/support/ast/variant.hpp>
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#include <boost/fusion/include/adapt_struct.hpp>
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#include <iostream>
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#include <string>
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#include <list>
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#include <numeric>
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namespace x3 = boost::spirit::x3;
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namespace client
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{
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///////////////////////////////////////////////////////////////////////////////
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// Semantic actions
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////////////////////////////////////////////////////////1///////////////////////
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namespace
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{
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using x3::_attr;
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auto do_int = [](auto& ctx) { std::cout << "push " << _attr(ctx) << std::endl; };
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auto do_add = []{ std::cout << "add\n"; };
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auto do_subt = []{ std::cout << "subtract\n"; };
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auto do_mult = []{ std::cout << "mult\n"; };
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auto do_div = []{ std::cout << "divide\n"; };
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auto do_neg = []{ std::cout << "negate\n"; };
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}
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///////////////////////////////////////////////////////////////////////////////
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// The calculator grammar
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///////////////////////////////////////////////////////////////////////////////
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namespace calculator_grammar
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{
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using x3::uint_;
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using x3::char_;
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x3::rule<class expression> const expression("expression");
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x3::rule<class term> const term("term");
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x3::rule<class factor> const factor("factor");
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auto const expression_def =
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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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auto const term_def =
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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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auto const factor_def =
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uint_ [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_DEFINE(
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expression
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, term
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, factor
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);
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auto calculator = expression;
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}
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using calculator_grammar::calculator;
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}
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///////////////////////////////////////////////////////////////////////////////
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// Main program
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///////////////////////////////////////////////////////////////////////////////
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int
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main()
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{
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std::cout << "/////////////////////////////////////////////////////////\n\n";
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std::cout << "Expression parser...\n\n";
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std::cout << "/////////////////////////////////////////////////////////\n\n";
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std::cout << "Type an expression...or [q or Q] to quit\n\n";
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typedef std::string::const_iterator iterator_type;
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std::string str;
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while (std::getline(std::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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auto& calc = client::calculator; // Our grammar
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iterator_type iter = str.begin();
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iterator_type end = str.end();
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boost::spirit::x3::ascii::space_type space;
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bool r = phrase_parse(iter, end, calc, space);
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if (r && iter == end)
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{
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std::cout << "-------------------------\n";
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std::cout << "Parsing succeeded\n";
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std::cout << "-------------------------\n";
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}
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else
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{
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std::string rest(iter, end);
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std::cout << "-------------------------\n";
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std::cout << "Parsing failed\n";
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std::cout << "stopped at: \"" << rest << "\"\n";
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std::cout << "-------------------------\n";
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}
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}
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std::cout << "Bye... :-) \n\n";
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return 0;
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}
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