Re: warning: unused value: $3

[henrik . sorensen]

On Friday 27 October 2006 00:12, you wrote:
> On Thu, 26 Oct 2006 address@hidden wrote:
> > > in semantic actions at any level in the parse tree.  Bison would have
> > > to check every possible expansion of every possible RHS symbol.  That
> > > implementation seems like more work than I want to do.
> >
> > ... but how hard would it be to check just one level ?
>
> Not as hard surely, but not trivial.  If warning about just the current
> rule is misleading, arbitrarily choosing to go only one level down seems
> just as confusing or more confusing in general.  
true, good point,
... but this is what you can realistically check,
> Then again, I try to 
> avoid mid-rules, $0, and $-n, so maybe I don't have the right feel for
> this.  
maybe disable the check completely if $0 or $-n is used.

What is the impact of the unused $n ?

> I think we need input from other users to get a better feel for 
> what's common.
I doubt there will be many uses of $0 beyond one level.
And also since bison are LALR(1) the restriction of checking by looking just 
one level ahead is not that far off.

Henrik