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Comment by jph00 | Hacker News Reader

Combinators are elegantly expressed in array languages, especially J. Here's a great recent paper with details : https://raw.githubusercontent.com/codereport/Content/main/Pu...

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Unfortunately (as an array language fan) this isn't really true. Certain function composition operators that exist in array languages appear to have similarity with combinators, however array languages are unable to express true lambda calculus style combinatory logic (without just implementing the reduction rules yourself, which defeats the point).

Can you expand on this some? I am not super familiar with the array-based group of languages, but so was under the impression that implementing S,K, and I combinators was possible. Is it just the restriction of array arguments or is it something else that inhibits the languages?

Yeah, you can implement them like you could in anything - it varies per language but the lack of true higher order functions (anything except K) and lazy evaluation (all) means that there's not really an 'elegant' way for anything more than 1 term deep.

That's not to say that the 'combinators' in array languages are bad, they're very useful and a nice form of function composition that I wish most other languages had, but they're not really a true combinator in the lambda calculus sense. You can't pass the array language 'combinators' to other combinators.

BQN[1] has higher order functions. Of the array languages I've used, it's by far my favourite. That said, I mostly solve small problems for fun in them.

[1] https://mlochbaum.github.io/BQN/index.html

Yeah BQN sort of has higher order functions but it still distinguishes between functions and data, so I don't think it would be that possible/easy to use combinatory logic style combinators. I haven't used BQN much though, so I could be wrong.

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