Re: [Bug-apl] crash on each of empty

[David B. Lamkins]

Thanks, Jürgen.

I'm comfortable with this resolution.

I noticed the same typos on p. 110 of the ISO spec. It didn't occur to
me, though, to substitute Z←(R) ≠ (R).

Best wishes,
  David

On Fri, 2014-05-16 at 16:40 +0200, Juergen Sauermann wrote:
> Hi David,
> 
> not sure if it contradicts.
> 
> (1) First of all the ISO standard says this about A f¨ B and f¨ B:
> 
> 9.2.6 Each
> ...
> For both forms:
>    If B is not empty, Signal domain-error.
> ...
> 
> I believe this is a typo and they mean "if B is empty". Thus according
> to the ISO standard +¨'' is undefined.
> 
> (2) Then we have the IBM language reference. On page 56, "Fill
> Function for Primitive Scalar Functions"
> they describe the fill function for scalar f (i.e. + in your example)
> which, as I read it, always returns
> values with numeric 0 for all simple ravel elements.
> 
> On page 110, Figure 20 they give a completely different definition of
> the fill function for scalar function
> as Z←(R) ≠ (L). As far as I can tell, both definitions are equivalent
> for dyadic scalar functions, but the
> definition on page 110 does not work for monadic scalar functions due
> to the lack of L. If we fix that by
> using Z←(R) ≠ (R) for monadic functions then both definitions become
> equivalent again.
> 
> GNU APL has hopefully implemented the description on page 56.
> 
> (3) But then, surprise, in IBM APL2 +¨'' returns:
> ┌⊖┐
> │ │
> └─┘
> while GNU APL returns:
>       +¨''
> ┌⊖┐
> │0│
> └─┘
> My best explanation for this that IBM may have used the same fill
> function for + as for user-defined functions.
> 
> I feel more comfortable with the written documentation of IBM APL2
> because it is rather difficult
> to implement things based on what another implementation produces.
> 
> /// Jürgen
> 
> 
> On 05/15/2014 06:49 PM, David B. Lamkins wrote:
> 
> > Thank you. Confirmed working with the original test cases.
> > 
> > Pushing a bit further, I believe that the following behavior may still
> > be contrary to the IBM spec in SVN 268:
> > 
> >       +¨''
> > ┌⊖┐
> > │0│
> > └─┘
> > 
> > Here we have a numeric function passed an empty character. Transforming
> > this via the identity given previously, we get the equivalent
> > expression:
> > 
> >       (⍴'')⍴⊂+↑''
> > DOMAIN ERROR
> >       (⍴'')⍴⊂+↑''
> >              ^^
> > 
> > (I don't know whether there's a corresponding case for ⍬. Is there a
> > primitive monadic function that only accepts character arguments?)
> > 
> > 
> > 
> > 
> > 
>