Re: FYI: default %printer/%destructor

[Hans Aberg]

On 25 Oct 2006, at 00:09, Joel E. Denny wrote:

> > <!> is really too hieroglyphic for
> > me.
>
> I realize <!> looks odd when considered in isolation, but I'm  
> trying to be
> consistent with a couple of other proposals....
>
> First, named semantic values:
>
>   exp(sum): exp(term1) '+' exp(term2) {
>     $sum = $term1 + $term2
>   }
>   ;
>
>   grammar(): defs() rules() epilogue(!) {
>     $grammar = new_grammar ($defs, $rules);
>   }
>   ;
>
> Here, () = unspecified value name = default name = the symbol  
> name.  That
> seems logical to me.  (!) = no value is used at all.  The ! conveys a
> sense of caution, which I think this is appropriate given that its  
> purpose
> would be to disable any Bison warning about unused $3.

I have looked at this, and tried to find an examples of other similar  
uses, though I failed. One variation might be
  exp/sum: exp/term1 '+' exp/term2 {...}
Instead of the proposed
  exp/sum -> exp/term1 '+' exp/term2 {...}
One might use UTF-8 input files, and the symbol U+2192 RIGHTWARDS  
ARROW "→"; thus:
  exp/sum → exp/term1 '+' exp/term2 {...}

This should solve the parsing problem of the .y files, I think.

  Hans Aberg