Any idea what Across 15 & 23's ⌶s are supposed to be?

What kind of puzzle is that D:

@Bubbler Which one, the one I linked to or the question about ⌶?

The crossword one.

@Bubbler Well, it is an APL crossword. You're supposed to fill in one character in each square so the expressions do/evaluate to what the clues say.

I once had a hard time with number crossword where all the clues were based on some unknown values, and this one is even worse...

And 25⌶ isn't a thing, is it?

@Bubbler No. Hence my question.

Ah, solved it. ⌶ should be ×.

Why you can do (⊃,⊃), but not (⍬⍴,⍬⍴)?

@lelf Trains are parsed from the right, grouping 3 items into one. So abcdefg becomes ab(cd(efg)).

⍬⍴,⍬⍴ means ⍬⍴(,⍬⍴), but ⍬ is not a function. So it's syntax error.

If you want it to do the same as (⊃,⊃), you can write (⍬∘⍴,⍬∘⍴).

@lelf ^ or alternatively (2⍴⍬⍴⊢)

CMC: Implement xnor's formula for my 20-cap set challenge.

Note that any affine transformation to the formula is also valid.