Thank you so much for a rapid answer. With no background into the history of the language, I would not have known where to look for this sort of thing.
I see now in Dyalog's "Mastering Dyalog APL, 1st Ed.", ~p372 "Specialists Section" there are discussions about this and related language differences. There are a few items to digest there in regards to their ⎕ML System Variable and how it handles APL2 (IBM) vs. Dyalog APL dialects. The more I explore, the more I question whether I must choose to study "the APL2 path" or "the Dyalog APL path" ... :) I hope I do not have to choose! So far, trying both dialects while learning has illuminated some concepts for me, but I fear I might confuse myself with implementation differences. Again, thank you very much for the insight. -Russ On Wed, 23 Dec 2020 at 23:21, Kacper Gutowski <mwgam...@gmail.com> wrote: > On Wed, Dec 23, 2020 at 10:46:13PM -0800, Russtopia wrote: > > [Dyalog] > > 9 2 9/↑'∘⌹∘' ' ⌹ ' > > ∘∘∘∘∘∘∘∘∘⌹⌹∘∘∘∘∘∘∘∘∘ > > ⌹⌹ > > > > [GNU] > > 9 2 9/↑'∘⌹∘' ' ⌹ ' > > ∘∘∘∘∘∘∘∘∘⌹⌹∘∘∘∘∘∘∘∘∘ > > > > Is it unexpected that GNU APL does not apply the Compress (/) across > > multiple right-hand items? > > There are some subtle differences in how / works in Dyalog and in GNU APL, > but here the reason is much more prosaic. > > By default the monadic ↑ and ⊃ are swapped in Dyalog. It has a setting > called ⎕ML that controls it, and if you set ⎕ML←2, it will interpret > this expression the same way GNU APL does: > > 9 2 9/⊃'∘⌹∘' ' ⌹ ' > ∘∘∘∘∘∘∘∘∘⌹⌹∘∘∘∘∘∘∘∘∘ > ⌹⌹ > > > -k >
