Re: Definition of "first-thingy"

[Jay Foad]

9≡⊂9 is pretty much the whole basis of "floating array theory", upon
which APL2 was based. Other array languages like Sharp APL and J went
in a different direction.

Once you accept the floating array model, this sentence seems
completely redundant, and I don't know why they put it in the spec:
"If B1 is a number or a character, set B to an array, whose ravel-list
contains the single
item B1 , and whose shape-list is empty."

Jay.

On Thu, 20 Feb 2020 at 15:12, Elias Mårtenson <address@hidden> wrote:
>
>
> ---------- Forwarded message ---------
> From: Elias Mårtenson <address@hidden>
> Date: Thu, 20 Feb 2020, 22:39
> Subject: Definition of "first-thingy"
> To: <address@hidden>
>
>
> One benefit of experimenting with low-level PAL behaviours is that I've spent 
> much more time lately reading the ISO spec.
>
> I was reading the specification for ↑ (first), which says that it returns 
> "first-thingy" of the argument.
>
> Now, the definitions section defines "first-thingy" as such:
>
> First-thingy in A : An opration that for A , an array, returns an array B , 
> defined as follows:
> If A is empty, set B1 to the typical-element of A .
> Otherwise, set B1 to the first-item of the ravel-list of A .
> If B1 is a number or a character, set B to an array, whose ravel-list 
> contains the single
> item B1 , and whose shape-list is empty.
> Otherwise, set B to B1 .
>
> My impression from reading this is that this is not consistent with GNU APL's 
> behaviour in the following case: ↑9
>
> GNU APL returns the number 9 in this case, while it would seem it's supposed 
> to return a 9 wrapped in a zero-dimensional array: ⊂9
>
> Now, GNU APL evaluates ⊂9 to the number 9 as well, which I also feel isn't 
> consistent.
>
> Am I misreading the spec, or is there an inconsistency here?
>
> Regards,
> Elias