Is there a way to set the initial state of the accumulator in Dyalog's reduce operator? As a contrived example, to count elements in a list l in Python I could say reduce(lambda acc, _: acc+1, l, 0) where the last argument is the initial state of acc at the first call of the lambda.

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@xpqz Evaluate one line of APL by prefixing it with ⋄. Use ⍞← instead for inline one-liner answers. Use ] to call user commands, including ]help ⍣ for help on a glyph etc. Do not use markdown, but fixed-width (4 initial spaces, Ctrl+K) is fine. Commands: )lb for language bar, )docs for full documentation, )ref for PDF reference card, )idioms for idiom list, )tio to create link or prefix code with f← for link to separated function assignment.

@xpqz i don't think there's a better way than just appending 0

@mappo Thanks. Logged as issue 17870.

@Adám It seems to me that tryapl.org is down. Not sure if that is just on my side or for everyone.

I'm confusing myself with vector shapes. If I have a vector-of-vectors, how do I append to it?

@xpqz
VALUE ERROR
      ll,('A' 65)
      ∧

@JPeroutek Indeed. We noticed it earlier too. I'll see what I can do.

@xpqz ,⊂ maybe?

Yes!

Hmm, I thought ∊ did what ⊂ infact does.

The reason is that you want to add another element, not append the elements of the additional vector to the existing elements.

@xpqz ∊ just unpacks all data into a simple list.