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I'm learning APL through APLX. I see a lot of code using the omega character, but whenever I try to look up what it means, I can't find any information. None of the APLX documentation mentions it, yet it appears in some of the sample code in the very same files. Additionally, the Wikipedia article on APL Syntax and Symbols uses an ⍵ in a block of sample code, yet does not have an explanation of what ⍵ does.

Does the omega even have a meaning in APLX? If not, what is its meaning in other versions of APL?

ren
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4 Answers4

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I can't speak for APLX, I'm a Dyalog-User. In Dyalog APL, ⍵ (0mega) is used in the context of dfns (dynamic functions) as placeholder for the right argument of the dfn. (And ⍺ is used for left arg). Sample:

      mean←{(+/⍵)÷⍴⍵}
      mean¨(2 3)(4 5)
 2.5  4.5
MBaas
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    Trying to find an answer to your question, I browsed the APLX Manual - but as you said, it is not mentioned in any explanatory way - so very likely it has no special use in APLX. The common use in the "APL Community" seems to be to use it (along with ⍺) as a placeholder for right/left arguments in "pseudo APL-ish" notation... BTW, are you aware that APLX has been discontinued? http://www.dyalog.com/dyalogue-newsletters.htm?nl=26&a=155 – MBaas Oct 21 '16 at 14:12
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    Oh, and BTW - the Wikipedia-Article uses the ⍵ in a "Dynamic function" (dfn), so it illustrates usage of ⍵ in Dyalog APL. – MBaas Oct 21 '16 at 14:14
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    Thanks for the info. Yeah I'm using APLX because it's now free, which is nice. I've been waiting for my educational licence of Dyalog APL, using APLX in the meantime. – ren Oct 22 '16 at 04:23
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In an APL dfn, the omega stands for the right argument.

square←{⍵×⍵} square 5 25 2 square 3 9

ein mensch
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  • In a _Dyalog APL_ dfn, that is. – Stormwind Oct 29 '16 at 15:51
  • This applies to other APL systems too – ein mensch Nov 01 '16 at 19:25
  • Which APL systems do in fact have dfns? I don't have the complete picture. – Stormwind Nov 19 '16 at 15:11
  • @Stormwind dfns are standard apl, so every complete system being dyalog, gnu, ... has dfns – ein mensch Nov 19 '16 at 15:12
  • Hmmm... are we talking about the same thing now? :-) I had the impression dfns were a typical (and even exclusive?) Dyalog APL thing...? Never heard of it being standard APL.... Could you give any pointers? APL2, APL2000, APLX, MicroAPL etc? As said i don't have the full picture re. this. – Stormwind Nov 19 '16 at 15:41
  • @Stormwind they work in gnu apl and ngn apl too (and morel but i just tested those) – ein mensch Nov 19 '16 at 15:50
  • Could it be that it's exactly these 3 ones, Dyalog initially, from which John Scholes' work then implemented in the gnu and the js implementations? But the last two ones are kinda new babies? :-) – Stormwind Nov 19 '16 at 16:04
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In "APL: the language and it's usage" by Polivka, Raymond, P. 1975 ISBN:0-13-038885-8 omega and alpha are shown as "undefined" on page 500. Therefore I imagine one can use them as variable names generally within APL.

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The right argument. It's the right argument for a function.

Ikura
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  • Could you extend a bit in your answer so the OP can understand better, also If you could include some source from where you deducted this would be great. – SirPeople Sep 01 '18 at 20:09
  • Extend what? Don't get it! – Ikura Sep 01 '18 at 20:12
  • Look at other answers, they provide wider answers. Your answer maybe right, but its not explained. Why is the right argument? Where is it written that it is the right argument? This kind of information could make your answer more useful – SirPeople Sep 01 '18 at 20:15