The APL Orchard

12:43 AM

Was trying to implement "pretty printing" of APL arrays, mimicking the ]box on style. I have to say, I just kept wishing Python was array oriented because manipulating all those strings was annoying as hell

I got the main things working, at least. May still have some hidden bugs, but some things already print decently:

 >> 2 2⍴⊂2 2⍴⍳4
┌──────┬──────┐
│ 0 1  │  0 1 │
│ 2 3  │  2 3 │
├──────┼──────┤
│ 0 1  │  0 1 │
│ 2 3  │  2 3 │
└──────┴──────┘

Bubbler

12:57 AM

Cool. Are the extra spaces around the center intended?

RGS

@Bubbler They were "intended" in that I put them in, but then didn't do the side margins with extra spaces, so I removed them meanwhile

Was doing some debugging, now I also got this:
        2 3⍴(1 2 3)(2 2⍴0)1(3 1⍴0J1 0.001 0)
┌───────┬───────┬─────┐
│ 1 2 3 │ 0 0   │1    │
│       │ 0 0   │     │
│       │       │     │
├───────┼───────┼─────┤
│   0J1 │ 1 2 3 │ 0 0 │
│ 0.001 │       │ 0 0 │
│     0 │       │     │
└───────┴───────┴─────┘

Bubbler

Oh wow... but that scalar

RGS

You mean the lonely 1? Dyalog APL prints this more or less like I have it there.... Except that Dyalog APL aligns decimal points and I think J's for complex numbers as well

Well, gotta go sleep. Ttyl

Bubbler

Good night.

(Just checked dfns.disp, and it gives all contents left-justified with no margins at all)

Adám

4:28 AM

@Bubbler @RGS it actually has an option to centre:

      0 1 disp 2 3⍴(1 2 3)(2 2⍴0)1(3 1⍴0J1 0.001 0)
┌───────┬─────┬───┐
│ 1 2 3 │ 0 0 │ 1 │
│       │ 0 0 │   │
├───────┼─────┼───┤
│0.000J1│     │0 0│
│0.001  │1 2 3│0 0│
│0      │     │   │
└───────┴─────┴───┘

Razetime

5:30 AM

@Adám for {P5.G.ln↓⍉↑⍵×⍺∘-@3⍳¨⍺1 1⍺}:

for {P5.G.ln↓⍉↑⍵×(⍳⍺)⍬⍬(⍺-⍳⍺)} :

Adám

@Razetime What is ⎕IO?

@Razetime No idea. @dzaima what is going on here?

Razetime

5:46 AM

@Adám ok , works with ⎕IO←0

Adám

@Razetime Then simply use 4 instead of 3 for ⎕IO←1 :-)

Razetime

@Adám he did say it was sort of unfinished

with ⎕IO←1

Adám

@Razetime Is tis right, or is that a stray line?

Razetime

stray line

it doesn't do this with ⎕IO←0

Adám

Oh, of course, ⎕IO affects the ⍳s too.

Razetime

6:11 AM

so that causes the stray

RGS

8:59 AM

@Adám I'm not gonna go down that rabbit hole

Elias Mårtenson

@Adám And that's why I never implemented ⎕IO :-)

Adám

@EliasMårtenson Good choice.

Elias Mårtenson

Last night I had this idea. In APL, you can modify arrays using the ← operation. Like foo[2;3] ← whatever. Now, when your language has immutable objects, this use of ← is not useful. However, the general idea of deriving an object based on some other with a subset of it modified is still useful. So a general syntax for this may be the following:

Let's choose the symbol ⇺ for immutable modification. Now, the expression foo[2;3] ⇺ 5 will return a new array, similar to foo but with one cell changed. So you could do something like foo ← foo[2;3] ⇺ 5 to create this new array, and reassign it to foo. You could even imagine a new operation, like ⇷ that would do the two things at the same time foo[2;3] ⇷ 5 which then would behave remarkably similar to the APL way of doing it, without having to suffer from modified arrays.

Please critique this idea.

It feels like this is something that someone must have done already. It's not particularly bleeding-edge language research.

Adám

9:15 AM

@EliasMårtenson Why require the array to be named? You could write something like 5@(⊂2 3)

Elias Mårtenson

It doesn't have to be named. I just used it as an example.

You can definitely do something like (⍳10)[4] ⇺ 100 this would evaluate to a n array: 0 1 2 100 4 5 6 7 8 9

Adám

So this is just a different syntax for the @ operator.

Elias Mårtenson

I figured someone thought about it already.

Adám

      100@4⍳10
1 2 3 100 5 6 7 8 9 10

Elias Mårtenson

This puts me in a dilemma. I was to be compatible with Dyalog where it makes sense, and this is a case where it makes sense. But I use @ for character literals already so I need to find a different character for that :-)

Adám

9:20 AM

@EliasMårtenson I told you back then that @ already was used, no?

Elias Mårtenson

Yes, but I didn't pay attention to what it was used for :-)

I didn't realise it may actually be a useful feature.

Adám

It is used for changing values at positions ;-)

However, implementing a "structural under" operator gives much more power.

Elias Mårtenson

My operation would be as generic as possible. Every operation/function would have a "modification method" that, if it exists, means that the ⇺ operation can be applied to it. So you could, for example, do something like: (↑x)⇺100 to modify the first element of an array.

Well, not modify. Return a new array with the first element replaced.

Adám

That is exactly what structural under does.

Elias Mårtenson

So is @ the structural under operation?

Adám

9:24 AM

No, but it should have been imo. We propose ⍢ for it, which is what Extended Dyalog APL and dzaima/APL use, and is probably what Dyalog will use if we ever get around to add it.

Elias Mårtenson

OK, sounds good, and I don't use that symbol yet :-)

Adám

Current Dyalog @ is but a subset of structural under.

@EliasMårtenson Just don't give it special syntax, please. Make it a normal operator!

Elias Mårtenson

Well, yes. The special part happens in the backend

Adám

So it'd be 100⍢↑x

Elias Mårtenson

OK. But what about structural change of a dyadic function?

Oh wait, You are applying an operator on a number?

Or did you mean to write 100↑⍢x

Adám

9:29 AM

@EliasMårtenson Yes.

@EliasMårtenson You'd write e.g. 100⍢(2∘↑)x

The idea is that an array is treated as the corresponding constant function.

Elias Mårtenson

I haven't implemented Dyalog style ∘ at this point, and I never considered doing it. Is there some good documentation somwhere that explains precisely how it works?

RGS

@EliasMårtenson You mean this?

Elias Mårtenson

9:45 AM

@RGS I mean exactly that. Thank you.

RGS

np, I'm gonna be here all morning :P

      ]create # C:/users/rodri/documents/test -source=both
Linked: # ←→ C:\users\rodri\documents\test
      ]link.list
┌─────────┬─────────────────────────────┬─────┐
│Namespace│Directory                    │Items│
├─────────┼─────────────────────────────┼─────┤
│#        │C:/users/rodri/documents/test│0    │
└─────────┴─────────────────────────────┴─────┘
      ]link.break #
Unlinked 0 items: #
      ]link.list
No active links

The message after ]link.break is very unclear

Adám

@RGS Can you make a GitHub issue about that, and explain what you'd want instead?

RGS

@Adám Yeah. Now I understand it says it unlinked 0 items because the link was syncing 0 things, and I thought it meant it broke 0 links. Maybe it is not that unclear, I am just a dummy

Elias Mårtenson

10:15 AM

Hmm, the ∘ operator makes sense. However, from a parsing perspective it collides with its use as the Null function (left argument of .). So I'd need to special-case it when building the AST.

Perhaps I should go back to my original idea of having outer join be a separate symbol, and not a special case of .

Adám

@EliasMårtenson Absolutely. That ∘. is a real wart. I suggest dyadic f\ and/or f⍀

RGS

Does anyone have the magic TIO apl incantation at hand?

Adám

@EliasMårtenson Also, should you ever want object.member syntax then I'd recommend even separating f.g outer product a different symbol.

Elias Mårtenson

KAP already supports ⌺ for outer join. I could easily use \ or ⍀ of course instead. What is the reasoning behind that?

Adám

@EliasMårtenson But ⌺ is used by Dyalog for stencil code.

@RGS tio.run/##SyzI0U2pTMzJT////3/ao7YJj3r7HnU1P@pd86h3y6H1xo/…

Elias Mårtenson

10:19 AM

@Adám Good point. Although I'll deal with that when the time comes :-)

@Adám Oh is it? I don't know what that is. And I thought that symbol was so appropriate :-)

Adám

@EliasMårtenson You can always look up symbols from the IDE, or even use APLcart.

@EliasMårtenson You could use ˙

Elias Mårtenson

@Adám I don't have Dyalog. I should probably install it.

@Adám sorry for a stupid question, but the IDE is not included in the free linux release?

Adám

@EliasMårtenson The GUI IDE (called RIDE) isn't. But it is easy to get from GitHub. Not a bad question at all, btw.

RGS

@Adám thanks...

Adám

@EliasMårtenson I'm trying to conserve glyphs, and dyadic f\ and f⍀ are not defined. J uses dyadic f/ for outer product.

RGS

10:32 AM

(@Adám turns out I was right after all: codegolf.meta.stackexchange.com/users/56656/wheat-wizard)

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