Re: FYI: default %printer/%destructor

[Hans Aberg]

On 19 Nov 2006, at 23:04, Joel E. Denny wrote:

> > > Ok, I think I miscommunicated.  The ambiguity I meant is whether  
> > > `b/c' is
> > > the same as `b/ c' as discussed below.  `c :b' and `c:b' have the  
> > > same
> > > issue....
> >
> > I think there should be normal tokenization the Bison .l file,  
> > with a general
> > rule, stripping out space and newlines. I think this leads to the  
> > most
> > intuitive grammar.
>
> I was thinking of the human reader not Bison's scanner.

Me too.

> > The %destructor is only needed with output language C.
>
> Currently, it's also useful for C++.

You mean, of one writes code in the common C/C++ subset. :-)

> There could be other target
> languages some day that need it as well

Perhaps, but I can't really think of any.

> > > If we use `:' for value names ...
> >
> > WHat do you mean by value names, here? Is that the semantic value  
> > variables?
>
> Yes.

Then I think ":" should be avoided.

> > > You mean exp:r?  I don't see how that's easier.
> >
> > It depends what comes first in the definition. It is easier  
> > implementing with
> > defined names first, and then the definee.
>
> I don't see how either is easier to implement than the other.

I guess this is something that show when tried. :-) I don't really know.

> > > How do you declare that the semantic value is unused but still  
> > > use the
> > > location?  Will we make the gamble that this is never necessary?
> >
> > I haven't considered this. Now that you mention this, I think some  
> > special
> > notation might be the prudent way. The location value will  
> > probably be used
> > more often with Bison improved parser diagnostics. This suggests  
> > that one
> > indeed needs some special way to indicate it.
>
> Ok, I hope you'll respond to my other email where I propose a more  
> concise
> alternative to exp($sum, @sum).

I will look at this, but tomorrow - it is getting late here. :-)

  Hans Aberg