Re: Empty arguments

[Dr . Jürgen Sauermann]

Hi Colin,

interesting. If I remember correctly then some older interpreters tried to implement special
properties (such as constructors to pretend support for object orientation) by means of
special labels in defined functions.

This idea apparently didn't make it into the ISO standard, most likely because no agreement
could be reached between the vendors that were participating in the standardization.

IBM APL2 has a similar quirk with special variable names S∆DEFN_NAME and T∆DEFN_NAME
which were then replaced by ⎕STOP and ⎕TRACE in the ISO standard.

I suppose the lack of standardization then convinced IBM to better drop the feature.

Best regards,
Jürgen

On 5/4/20 9:35 PM, Colin Verrilli wrote:

I have a copy of the first edition APL2 LRM from 1982. It specifies two special System Labels: ⎕FL and ⎕ID. ⎕FL: was used to label the fill function so that the programmer could specify precisely what the fill function should be within the scope of the function definition. Similarly, ⎕ID was used to denote the identity operation (for defined operators with empty arguments). This facility was removed from later versions of the manual. There must have been some issue with this approach. Any ideas?

On Mon, May 4, 2020 at 1:08 PM Kacper Gutowski <address@hidden> wrote:

On Mon, May 04, 2020 at 10:43:25AM +0100, Jay Foad wrote:
>Interesting. Dyalog APL is different: if you apply f¨ to empty
>argument(s), it applies f once to the prototypical items of the
>argument(s) to determine the prototypical item of the result.

Yes, I liked the idea until I realized this includes side effects.

>I'm not sure what NARS2000 does.

DOMAIN ERROR


-k