Re: [Bug-apl] A few problems

[Dr . Jürgen Sauermann]

Hi,

I am pretty sure that GNU APL behaves according to the ISO
standard up to the point where it crashes. The only wrong
behaviour that I currently see is that it should catch the bad
alloc exception and signal WS full instead of looping forever.
I will look into this.

Thanks. Every design decision depends on local constraints. Though,
why not to use look-ahead and detect that as incorrect assignment to a
function? I see it as a more direct and clean approach. Would it be
too difficult to implement?

With best regards.

There are a nu,ber of reasons for not doing this. The first one that comes to my mind
is that assignments are only one case of a niladic function causing infinite recursion. Considert

∇A
 A+1
HALT: 'HALTED'
∇

∇B
 B×1
HALT: 'HALTED'
∇

∇C
 A+G
HALT: 'HALTED'
∇
...

All ot them are legal APL and would make perfectly sense if  each function
would contain a check that terminates the recursion. As far as I understand
computer science, this directly leads to the halting problem which is known
to be not decidable.

Attempting to solve a not decidable problem at runtime is nothing
that I would dare to try.

Best Regards,
/// Jürgen Sauermann