Boost C++ Libraries

libs/spirit/example/qi/calc6/calc6b.hpp

/*=============================================================================
    Copyright (c) 2001-2010 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)
=============================================================================*/
#if !defined(BOOST_SPIRIT_CALC6B)
#define BOOST_SPIRIT_CALC6B

#include "calc6.hpp"

///////////////////////////////////////////////////////////////////////////////
//  Our expression grammar and compiler
///////////////////////////////////////////////////////////////////////////////
template <typename Iterator>
expression<Iterator>::expression(std::vector<int>& code, qi::symbols<char, int>& vars)
  : expression::base_type(expr)
  , code(code)
  , vars(vars)
  , op(code)
{
    using qi::lexeme;
    using qi::uint_;
    using namespace qi::labels;
    using qi::on_error;
    using qi::fail;
    using ascii::alnum;

    expr =
        additive_expr.alias()
        ;

    additive_expr =
        multiplicative_expr
        >> *(   ('+' > multiplicative_expr  [op(op_add)])
            |   ('-' > multiplicative_expr  [op(op_sub)])
            )
        ;

    multiplicative_expr =
        unary_expr
        >> *(   ('*' > unary_expr           [op(op_mul)])
            |   ('/' > unary_expr           [op(op_div)])
            )
        ;

    unary_expr =
            primary_expr
        |   ('-' > primary_expr             [op(op_neg)])
        |   ('+' > primary_expr)
        ;

    primary_expr =
        uint_                               [op(op_int, _1)]
        |   variable
        |   '(' > expr > ')'
        ;

    variable =
        (
            lexeme[
                vars
                >> !(alnum | '_')           // make sure we have whole words
            ]
        )                                   [op(op_load, _1)]
        ;

    expr.name("expression");
    additive_expr.name("additive-expression");
    multiplicative_expr.name("multiplicative-expression");
    unary_expr.name("unary-expression");
    primary_expr.name("primary-expression");
    variable.name("variable");

    on_error<fail>(expr, error_handler(_4, _3, _2));
}

#endif