@hyper-neutrino Can you give chat.stackexchange.com/users/537199/user1130590 access?

@Adám done

New record?

@user1130590 Welcome. You should now have access. Since you're new to Stack Exchange chat, I highly recommend reading apl.wiki/APL_Orchard#Features. Feel free to introduce yourself too.

@Adám, I feel I should know the answer to this question, but I don't. How do I merge an array of characters into a string?

⋄ '123'≡⍕⍳3 ⋄ '123'≡,⍕⍳3 ⋄ 'ABC'≡,/'A' 'B' 'C'

@AlexB
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reduction will always reduce the rank, so your vector (of vectors) becomes enclosed to a scalar, ⊃,/ will do the trick.

However, in many cases, you can just use ∊

@AlexB What are you trying to say/ask with the first two expressions?

⋄ '123'≡⊃⍕⍳3 ⋄ '123'≡⊃,⍕⍳3 ⋄ 'ABC'≡⊃,/'A' 'B' 'C'

@AlexB
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⋄ '123'≡∊⍕⍳3 ⋄ '123'≡∊,⍕⍳3 ⋄ 'ABC'≡∊,/'A' 'B' 'C'

⍕⍳3 will create a single character vector (with spaces). You'll want ∊⍕¨

@Adám I want to get a numeric string '123'

There's no such thing as "a numeric string".

You want the number 123?

@Adám You're right. I want a string that "looks like" a number.

@Adám This works. Thanks!

I didn't realize that ⍕ inserts spaces.

it gives a simple char array that looks like its arg

I should have known...

⋄ ≢⍕⍳3

@AlexB 5

:)

if all your elements are digits 0-9 there's a faster way

Coming from other languages, I find this behavior a bit quirky. In most languages, merging chars does not result in any format.

@Adám this sounds like Python's repr()

@Adám which is...?

@AlexB JavaScript: "1,2,3"===[1,2,3].toString()

@Adám ha ha... JS is not a language... it's marginally better than PHP... absolutely horrifying...

@AlexB No, ⍕ just gives an "image" back, not an expression.

(at most JS and PHP are slangs — pidgin latin)

@AlexB Assuming ⎕IO←0: ⎕D[array]

@Adám ah, cool

@user1027871 Hi bienjensu. If you want to participate here, please email access@apl.chat

@AlexB but most langs provide some generic toString for arbitrary objects that can generate whatever they want. APLs ⍕ is that, always returning a string that Somehow™ represents the argument. It's what you get as a printout from ⎕← or whatever

@dzaima OK, so like Python's repr(). String equivalent of data struct.

Hey, say I have two arrays as described in this paste here sciops.net/paste/1642272589.3f6fe672. How would I return 'board' with the zeros replaced with corresponding elements from 'check'?

@AlexB it's more like str() really

@Adám thank you, I applied for access a while ago but never posted in the end.

@dzaima I guess you're right. repr() ought to return something that looks like the constructor.

(anyway, back to APL... ehm...)

APL's repr is ⎕SE.Dyalog.Utils.repObj

@user1027871 (check/⍨⍥,zeros←0=board)@{zeros}board works

I had check[idx]@(idx←⍸0=board)⊢board

yeah

I was trying to avoid the ⍸ for efficiency but / is probably not efficient either

If you want in-place updating of board you can do board[idx]←check[idx←⍸0=board]

check⊣@(0∘=)¨board is short (but probably slow)

Ouch.

would be nice if you didn't need the ¨ there

but then I suppose that breaks the case where you know what elements you want :/

check{⍺⊣⍣(0=⍵)⊢⍵}¨board too.

Most elegant? board(,¨⊃¨⍨0=⊣)check

nah :P it's nice but ⊣@(0∘=)¨ is nicer if not going for speed

(⊢⌿⊢⊖⍨0=⊢⌿)↑check board is cute too.

yeah, that's nice

Speed doesn't really matter here, because board is already a bad array for speed.

thank you for the help

Well, I hope we didn't confuse you with too much information!

I'm spending some time comprehending the terser solutions, haha

Let us know if you want any explained.