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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