About passing parameters to yylex

[Jesus M. Diaz Hernandez]

Hi, i'm working with the c++ parser generator genarated by flex, but i
need to pass a parameter to the function yylex(). I follow the steps:

1.- i declare a new prototype for my lexical function and i set the
%option yyclass= to the class i'm defining:


%{
#include "Parser.h"

#undef YY_DECL
#define YY_DECL int Lexer::yylex (YYSTYPE* yylval)

%}

2.- in Parser.h,  i define the new lexer class:
...
class Lexer : public yyFlexLexer {
public:
 Lexer(istream* arg_yyin = 0, ostream* arg_yyout = 0 );

 int yylex(YYSTYPE* yylval);
};

3.- in a .C file i wrote the implementation of the constructor:
(i wrote it on the .y file)

Lexer::Lexer (istream* arg_yyin = 0, ostream* arg_yyout = 0)
 : yyFlexLexer(arg_yyin,arg_yyout) {};

then, i get a link error: 

parser/sforza.tab.o: In function `Lexer::Lexer(istream *, ostream *)':
/home/jesus/wdir/sforza/sforza.y:1038: undefined reference to `Lexer
virtual table'

That confuses me...if somone can help, i will apreciate it ;)

-- 
 Jesus Miguel Diaz Hdez
 __________________________________

 Grupo de Redes
 Facultad de Matematica y Cibernetica
 Universidad de la Habana, Cuba

e-mail:
   address@hidden