From:  Rav <PaulR@cais.com>
Date:  05 Feb 2018 22:19:08 Hong Kong Time
Newsgroup:  news.alt119.net/comp.lang.apl
Subject:  

Re: [Apl Nars] Why it is different?

NNTP-Posting-Host:  null

On 2/5/2018 8:48 AM, asetofsymbols@gmail.com wrote:
> If i have one array of 1 element
> if I eliminate that element of array
> what remain is a void list
> Without type of the first element
> 
> Possible there are other reasons for retain it type (but are not so clear to me)
> 
> Than why make different the void string '' from the void list ⍬ ?
> 
> Why not make ''=⍬?
> 

Take a look at http://www.sudleyplace.com/APL/Prototype%20Functions.pdf 
(by Bob Smith, the author of NARS2000).

The APL community is "full" of what are called empty vector jokes.  That 
article starts with one.  The point is that an empty vector is not 
different than a vector that contains elements -- it just happens to 
contain zero of them.  It is NOT "nothing."  Otherwise, it still retains 
the other characteristics that the original vector contained, i.e. 
datatype and depth, and even shape.  For example:

       3↑2↓(1 2 3) (4 5 6)
  0 0 0  0 0 0  0 0 0

Anyway, that article does a much better job than I can of explaining.