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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)
- =============================================================================*/
- ///////////////////////////////////////////////////////////////////////////////
- //
- // Yet another calculator example! This time, we will compile to a simple
- // virtual machine. This is actually one of the very first Spirit example
- // circa 2000. Now, it's ported to Spirit2 (and X3).
- //
- // [ JDG Sometime 2000 ] pre-boost
- // [ JDG September 18, 2002 ] spirit1
- // [ JDG April 8, 2007 ] spirit2
- // [ JDG February 18, 2011 ] Pure attributes. No semantic actions.
- // [ JDG April 9, 2014 ] Spirit X3 (from qi calc6)
- //
- ///////////////////////////////////////////////////////////////////////////////
- ///////////////////////////////////////////////////////////////////////////////
- // Uncomment this if you want to enable debugging
- //#define BOOST_SPIRIT_X3_DEBUG
- #if defined(_MSC_VER)
- # pragma warning(disable: 4345)
- #endif
- #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 expression;
- struct operand : x3::variant<
- nil
- , unsigned int
- , x3::forward_ast<signed_>
- , x3::forward_ast<expression>
- >
- {
- using base_type::base_type;
- using base_type::operator=;
- };
- struct signed_
- {
- char sign;
- operand operand_;
- };
- struct operation
- {
- char operator_;
- operand operand_;
- };
- struct expression
- {
- 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::expression,
- first, rest
- )
- namespace client
- {
- ///////////////////////////////////////////////////////////////////////////
- // The Virtual Machine
- ///////////////////////////////////////////////////////////////////////////
- enum byte_code
- {
- op_neg, // negate the top stack entry
- op_add, // add top two stack entries
- op_sub, // subtract top two stack entries
- op_mul, // multiply top two stack entries
- op_div, // divide top two stack entries
- op_int, // push constant integer into the stack
- };
- class vmachine
- {
- public:
- vmachine(unsigned stackSize = 4096)
- : stack(stackSize)
- , stack_ptr(stack.begin())
- {
- }
- int top() const { return stack_ptr[-1]; };
- void execute(std::vector<int> const& code);
- private:
- std::vector<int> stack;
- std::vector<int>::iterator stack_ptr;
- };
- void vmachine::execute(std::vector<int> const& code)
- {
- std::vector<int>::const_iterator pc = code.begin();
- stack_ptr = stack.begin();
- while (pc != code.end())
- {
- switch (*pc++)
- {
- case op_neg:
- stack_ptr[-1] = -stack_ptr[-1];
- break;
- case op_add:
- --stack_ptr;
- stack_ptr[-1] += stack_ptr[0];
- break;
- case op_sub:
- --stack_ptr;
- stack_ptr[-1] -= stack_ptr[0];
- break;
- case op_mul:
- --stack_ptr;
- stack_ptr[-1] *= stack_ptr[0];
- break;
- case op_div:
- --stack_ptr;
- stack_ptr[-1] /= stack_ptr[0];
- break;
- case op_int:
- *stack_ptr++ = *pc++;
- break;
- }
- }
- }
- ///////////////////////////////////////////////////////////////////////////
- // The Compiler
- ///////////////////////////////////////////////////////////////////////////
- struct compiler
- {
- typedef void result_type;
- std::vector<int>& code;
- compiler(std::vector<int>& code)
- : code(code) {}
- void operator()(ast::nil) const { BOOST_ASSERT(0); }
- void operator()(unsigned int n) const
- {
- code.push_back(op_int);
- code.push_back(n);
- }
- void operator()(ast::operation const& x) const
- {
- boost::apply_visitor(*this, x.operand_);
- switch (x.operator_)
- {
- case '+': code.push_back(op_add); break;
- case '-': code.push_back(op_sub); break;
- case '*': code.push_back(op_mul); break;
- case '/': code.push_back(op_div); break;
- default: BOOST_ASSERT(0); break;
- }
- }
- void operator()(ast::signed_ const& x) const
- {
- boost::apply_visitor(*this, x.operand_);
- switch (x.sign)
- {
- case '-': code.push_back(op_neg); break;
- case '+': break;
- default: BOOST_ASSERT(0); break;
- }
- }
- void operator()(ast::expression const& x) const
- {
- boost::apply_visitor(*this, x.first);
- for (ast::operation const& oper : x.rest)
- {
- (*this)(oper);
- }
- }
- };
- ///////////////////////////////////////////////////////////////////////////////
- // 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::expression> const expression("expression");
- x3::rule<term_class, ast::expression> 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::expression ast_expression;
- typedef client::compiler compiler;
- std::string str;
- while (std::getline(std::cin, str))
- {
- if (str.empty() || str[0] == 'q' || str[0] == 'Q')
- break;
- client::vmachine mach; // Our virtual machine
- std::vector<int> code; // Our VM code
- auto& calc = client::calculator; // Our grammar
- ast_expression expression; // Our program (AST)
- compiler compile(code); // Compiles the program
- iterator_type iter = str.begin();
- iterator_type const end = str.end();
- boost::spirit::x3::ascii::space_type space;
- bool r = phrase_parse(iter, end, calc, space, expression);
- if (r && iter == end)
- {
- std::cout << "-------------------------\n";
- std::cout << "Parsing succeeded\n";
- compile(expression);
- mach.execute(code);
- std::cout << "\nResult: " << mach.top() << std::endl;
- std::cout << "-------------------------\n";
- }
- else
- {
- std::string rest(iter, end);
- std::cout << "-------------------------\n";
- std::cout << "Parsing failed\n";
- std::cout << "-------------------------\n";
- }
- }
- std::cout << "Bye... :-) \n\n";
- return 0;
- }
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