@GreenSaguaro really you need just (⊂⍬); ⍬ is an empty list, but ⍬⍬ is a 2-item list of empty lists; ~⍬ removes all items that are in the empty list (but it's empty, so you remove nothing)

There’s also compress.

⋄ F←{2|⍵}⋄{(F⍵)/⍵}⍳10

@doug 1 3 5 7 9

and now it's gone full circle - compress to ~⊂⍬ to ~⍬⍬ to ~⊂⍬ to compress

Are nullary functions possible in Dyalog APL? I have an action that does not take parameters that generates random data, and I want to run it multiple times

⋄{17} 2

@doug 17

Yes but you need to call them with an arbitrary argument.

⋄{17}

@doug (1 trailing line)
{17}

␄

@doug Ah, I see. Thank you.

@GreenSaguaro @doug Yes, but not dfns or tacit functions; only tradfns:

      ∇r←rand10
       r←?10
      ∇
      rand10
1
      rand10
3
      rand10
4
      rand10
1
      rand10
5

@smartmic Hi there. Interested in APL?

@AviFS #nial on the APL Farm is relatively active.

@Adám Ah neat, will have to check it out later.

The APL wiki mentions a couple things as being noteworthy, but it doesn't mention the error handling. It looks like Nial has a native "fault" data type. Which means you can do:

     1 ÷ 0
?div
     5 ÷ 5 10 0 8
1. 0.5 ?div 0.625

Which means you can even error handle in the matrix-based style with something like:

     0@(?div∘=)5÷5 10 1 8
1 0.5 0 0.625

By all means, feel free to expand this (and anything) on the wiki.

Roughly translated into APL from:

     % A basic divide by zero error: ;
     1 / 0
?div
     % Errors are values called faults.
       This allows for powerful error handling: ;
     5 / 5 10 0 8
1. 0.5 ?div 0.625
     each (op x (if isfault x then 0 else x endif)) (5 / 5 10 0 8)
1. 0.5 0 0.625

     % You can also define custom faults using 'fault': ;
     fault 'this_is_an_error'
?this_is_an_error

     % Or by using a fault literal: ;
     ?this_is_an_error
?this_is_an_error

@Adám Good point. Is this way of error handling with a native vectorizable data type a known idea in the APL world?

Does Dyalog (or bqn/ngn/extended/j/k) have an analog?

@AviFS Well, NARS2000 and J can return infinities and indeterminates, while k has nulls…

@Adám @doug Thank you for your help with my unmatched bracket question!

> You can traverse and update a state with {state←initial_value ⋄ expression state⊣{traverser}¨⍵}

This state machine form is neat, thanks!

CMC restricted-source: Write an expression which, under Dyalog Unicode, returns … (scalar or vector) but under Classic returns ... without your code containing the … character.

Additional restriction: Under Classic, you must not cause the … character to exist at any time, so evaluating ⎕UCS 8230 isn't allowed under Classic.

Announcement: New job opening at Dyalog Ltd.

@Adám does classic edition has ⎕AVU?

@Adám Hi @Adám, yes, definitely! I am just looking around the various resources for learning APL. I was using J for some experiments a while ago but felt like giving the original a try. Have not regretted it so far. I mean I just spend a few hours getting my feet wet in the language but I am surprised how much I like the symbol notation much more than its ASCII equivalent in J…

@LdBeth Yes. In fact, that's the only version where it is really important.

@smartmic Great. Let us know if you need anything in particular. I trust you've found apl.wiki/learning_resources?