[m-rev.] for review: atoms in the debugger

[Fergus Henderson]

On 04-Jan-2002, Zoltan Somogyi <zs at cs.mu.OZ.AU> wrote:
> > > No it wouldn't. The formulae are an obvious consequence of the task of the
> > > predicate and the meaning of the input data.
> > 
> > It wasn't obvious to me.
> > I had to think about it for a fair bit.
> 
> Not enough.

Indeed! 

Either my brain has stopped functioning properly (a definite possibility ;-),
or it really isn't obvious.

> I added the comments
> 	% "()", plus Arity-1 times ", "
> and
> 	% "()", " = ", plus Arity-2 times ", "
> in the two arms.

Thanks.

> > > This is not an error message for a function application. It is a
> > > compressed representation for an atom. Deleting the +1 would be
> > > misleading. 
> > Why?
> 
> Because it would imply that there are only n-1 subterms available to be
> browsed, when in fact there are n. It implies that the browser command "^n"
> would fail, when in fact it would succeed.

OK, that makes sense.  If we're treating the function return value as the
"Arity+1"th argument for the purpose of browsing, then I agree it's a
good idea to use the +1 notation.

I'm not sure it's such a great idea to treat the function return value
as the "Arity+1"th argument -- it might be better to use something different,
e.g. "^r", to access the function return value -- but I'm not going to start
redesigning that at this point.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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