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13432 :: How to pass a closure iterator with arguments as an argument to a function

• rusty (orginal) [2025-09-28T06:27:16+02:00] view original

  Hi,

  As a fairly new but mostly happy Nim user, I have a question whose answer has so far eluded me, despite some trial and error and some googling. I have a closure iterator that works, as long as the iterator itself doesn't take any arguments. I pass that iterator as an argument to a function. That also works. But I can't figure out how to declare an iterator that accepts one or more arguments and then pass the iterator to a function and get that to work. Google AI hallucinated an example that failed with type errors, which is what I'm getting.

  I'm not posting my failed code, since I don't want help in fixing it (that's my job). All I need is an example that works in nim-2.2.4.

  Thanks.

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• janAkali (orginal) [2025-09-28T11:45:59+02:00] view original

  
  proc processNumbers(iter: iterator(a, b: int): int) =
    for i in iter(7, 2):
      echo i
  
  iterator myCountUp(max, incr: int): int {.closure.} =
    var i = 0
    while i <= max:
      yield i
      i += incr
  
  processNumbers(myCountUp)
  Run

  Interactive: https://play.nim-lang.org/#pasty=tNtjqhEL

  Need more info or some examples what you're trying to do if this doesn't help.

  Google AI hallucinated an example

  Deepseek, in my experience, is best for Nim (still gets a lot of stuff wrong), Claude is OK, everything else is pretty much unusable.

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• mabon (orginal) [2025-09-28T12:52:00+02:00] view original

  Why not give Gork a try

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• rusty (orginal) [2025-09-28T13:30:29+02:00] view original

  Thanks much @janAkali for your suggested code (and your advice about which LLMs might provide useful info). I had already found another method that I think may suffice for my needs: I wrote an iterator-generating proc that takes the argument that I want passed to the iterator, then coded the iterator inside the proc so it has access to the arg within the scope of the proc (no need to pass the arg to the iterator itself), then return the iterator as the return value of the proc. I can then reuse the same proc to create other similar iterators with different arg values.

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