Re: Problem with precedence and symbolic tokens

[T. S. Ferreira]

I got it. My application has lots of operators and I was looking for
some way of simplifying my grammar but there seems to be no other way.

Thanks a lot.

-- tsf


On Mon, Mar 17, 2008 at 3:51 PM, Hans Aberg <address@hidden> wrote:
> It just looks at the tokens in the rules, so you can't throw in extra
>  rules like you have done below. That is, AddOp must be expanded into
>  two rules "Expr: ...".
>
>  Look in the .outout file for the S/R conflicts, and the tokens
>  immediately before and after the parsing position dot ".".
>
>    Hans Aberg
>
>
>
>
>  On 17 Mar 2008, at 19:30, T. S. Ferreira wrote:
>
>  > I am trying to use precedences in Bison. After several trials, a
>  > simplified version of the relevant part of my input file is (it is
>  > supposed to produce reversed Polish notation):
>  >
>  > ----------------------------------------------------------------------
>  > --------------
>  > %{ ... %}
>  >
>  > %left ADD
>  > %left MULT
>  > %right EXP
>  > %left UNARY
>  >
>  > %%
>  > ...
>  > Expr
>  >         : Expr AddOp  Expr   %prec ADD    { printf("+"); }
>  >         | Expr MultOp Expr   %prec MULT   { printf("*"); }
>  >         | Expr ExpOp  Expr   %prec EXP     { printf("^"); }
>  >         | 'a'                                               { printf
>  > ("a"); }
>  >         | '(' Expr ')'
>  >         | '-' Expr                  %prec UNARY  { printf("~"); }
>  >         ;
>  > AddOp
>  >         :  '+'
>  >         |  '-'
>  >         ;
>  > MultOp
>  >         :  '*'
>  >         |  '/'
>  > ExpOp
>  >         :  '^'
>  >         ;
>  > %%
>  > ...
>  > ----------------------------------------------------------------------
>  > --------
>  >
>  > Unfortunately precedences do not seem to work. On the other hand, if I
>  > replace operator nonterminals by (like Addop) their symbols ('+') and
>  > put specs like %left '+', it works (without any %prec).
>  >
>  > Any hints?
>  >
>  > -- tsf
>  >
>  >
>  > _______________________________________________
>  > address@hidden http://lists.gnu.org/mailman/listinfo/help-bison
>
>



-- 
T. S. Ferreira