From:  Elijah Stone <elronnd@elronnd.net>
Date:  16 Nov 2020 15:31:12 Hong Kong Time
Newsgroup:  news.alt119.net/comp.lang.apl
Subject:  

Re: Problem with Dyalog's arctanh function?

NNTP-Posting-Host:  null

On Thu, 12 Nov 2020, J. Clarke wrote:
> This is kind of the old story.  When there's more than one way to do 
> something and no sound reason to prefer one over the other, let the user 
> or the developer decide.  We do it with quad-IO, why not with the branch 
> directions on complex calculations?

FWIW I have always thought ⎕io was not a great idea.  Most people I have 
spoken to on the matter feel similarly.

Any publication on APL needs to specify whether it has ⎕io as 1 or 0. (Or 
do the trick where you add/subtract ⎕io to/from indices, which is if 
anything even worse.)  It bifurcates the language and makes it harder to 
reason about as a unity.

If you need a trig function with branch cut that goes the other way, 
define one inline.  It's a fairly niche use-case, and not a particularly 
burdensome definition; and it alleviates the main language of overloads.

  -E