Re: [Boost-users] error boost spirit

Subject: Re: [Boost-users] error boost spirit
From: Raindog (raindog_at_[hidden])
Date: 2010-05-18 13:49:18

On 5/18/2010 8:40 AM, khaled hamidouche wrote:
> Hello
>
> with Joel Falcou we are wondring to write a parser to parse 
> mathematical expression like  (N1*3+N2/N3) ...
> with N1, N2, N3 are variables where their value are in an std vector
>
> so I take the calc example and I change it.
>
> my code looks like this
>
>
> #include <boost/config/warning_disable.hpp>
> #include <boost/spirit/include/qi.hpp>
> #include <boost/spirit/include/phoenix_operator.hpp>
> #include <boost/spirit/home/phoenix/container.hpp>
>
>
> #include <iostream>
> #include <string>
> #include <vector>
>
> namespace client
> {
>     namespace qi = boost::spirit::qi;
>     namespace ascii = boost::spirit::ascii;
>
>
>      void do_add()       { std::cout << "add\n"; }
>
>     
> ///////////////////////////////////////////////////////////////////////////
>     //  Our calculator grammar
>     
> ///////////////////////////////////////////////////////////////////////////
>     template <typename Iterator>
>     struct calculator : qi::grammar<Iterator, int(), ascii::space_type>
>     {
>         calculator(std::vector<int> const & vec) : 
> calculator::base_type(expression), vect(vec)
>         {
>             using qi::_val;
>             using qi::_1;
>             using qi::uint_;
>             using ascii::char_;
>
>             int index;
>
>
> //             vect.resize(3);
> //
> //
> //             vect[0]=10;
> //             vect[1]=11;
> //             vect[2]=12;
>                //vect=vec;
>
>             expression =
>                 term                            [_val = _1]
> >> *(   ('+' >> term            [_val += _1])
>                     |   ('-' >> term            [_val -= _1])
>                     )
>                 ;
>
>             term =
>                 factor                          [_val = _1]
> >> *(   ('*' >> factor          [_val *= _1])
>                     |   ('/' >> factor          [_val /= _1])
>                     )
>                 ;
>
>             factor =
>                 uint_                           [_val = _1]
>                 |   char_ >>uint_               [_val = at(vect,_1)]
>                 |   '(' >> expression           [_val = _1] >> ')'
>                 |   ('-' >> factor              [_val = -_1])
>                 |   ('+' >> factor              [_val = _1])
>                 ;
>         }
>
>         qi::rule<Iterator, int(), ascii::space_type> expression, term, 
> factor;
>         std::vector<int> vect;
>
>     };
> }
>
> ///////////////////////////////////////////////////////////////////////////////
> //  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";
>
>     using boost::spirit::ascii::space;
>     typedef std::string::const_iterator iterator_type;
>     typedef client::calculator<iterator_type> calculator;
>
>     std::vector<int> vec(3);
>     vec[0]=10;
>     vec[1]=11;
>     vec[2]=12;
>
>     calculator calc(vec); // Our grammar
>
>     std::string str;
>     int result;
>
>     while (std::getline(std::cin, str))
>     {
>         if (str.empty() || str[0] == 'q' || str[0] == 'Q')
>             break;
>
>         std::string::const_iterator iter = str.begin();
>         std::string::const_iterator end = str.end();
>         bool r = phrase_parse(iter, end, calc, space, result);
>
>         if (r && iter == end)
>         {
>             std::cout << "-------------------------\n";
>             std::cout << "Parsing succeeded\n";
>             std::cout << "result = " << result << std::endl;
>             std::cout << "-------------------------\n";
>         }
>         else
>         {
>             std::string rest(iter, end);
>             std::cout << "-------------------------\n";
>             std::cout << "Parsing failed\n";
>             std::cout << "stopped at: \": " << rest << "\"\n";
>             std::cout << "-------------------------\n";
>         }
>     }
>
>     std::cout << "Bye... :-) \n\n";
>     return 0;
> }
>
>
>
> when I compile I get this error
>
>
> /home/hamidou/LLVM/parser /main.cpp:296:   instantiated from here
> /usr/local/include/boost-1_42/boost/spirit/home/phoenix/core/detail/function_eval.hpp:135: 
> error: invalid initialization of reference of type ‘int&’ from 
> expression of type ‘const int’
> Process terminated with status 1 (0 minutes, 11 seconds)
> 1 errors, 1 warnings
>
>
> when I remove the use of the vector vect inside my grammar  it works 
> fine !!
>
> So, please what I did wrong ??
>
> Thank you so much for helping me
>
>
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