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5384 :: Passing iterators

• cdunn2001 (orginal) [2019-10-22T16:30:15+02:00] view original

  I'm trying to pass an iterator to a proc, the way I pass a generator in Python. I've submitted a bug: https://github.com/nim-lang/Nim/issues/12487

  I have a feeling it's not really a bug, and I'm just doing it wrong. I have searched this Forum, but nothing I've found has worked. Any ideas?

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• cdunn2001 (orginal) [2019-10-22T18:37:58+02:00] view original

  My best guess is that there is a problem when an iterator parameter is passed as "var". Or I might just be doing something wrong.

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• jyapayne (orginal) [2019-10-22T19:39:51+02:00] view original

  This seems to work for me:

  template toClosure*(i): auto =
    iterator j: type(i) {.closure.} =
      for x in i:
        yield x
    j
  
  iterator countUp(i, j: int): int =
    for g in i..<j:
      yield g
  
  proc takeInCountUp(iter: iterator) =
    for j in iter():
      echo j
  
  takeInCountUp(toClosure(countUp(0, 100)))
  Run

  So it's likely there is something else going on.

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• cdunn2001 (orginal) [2019-10-22T19:55:13+02:00] view original

  Hmm. This works too:

  import typetraits
  
  template toClosure*(i): auto =
    iterator j: type(i) {.closure.} =
      for x in i:
        yield x
    j
  
  iterator countUp(i, j: int, k: var string): int =
    for g in i..<j:
      k = $g
      yield g
  
  proc takeInCountUp(iter: iterator, k: var string) =
    for j in iter():
      echo j, " $", k
  
  var hello = "world"
  var x = toClosure(countUp(0, 3, hello))
  echo "type:", x.type.name
  takeInCountUp(x, hello)
  Run

  
  type:iterator (): int{.closure, locks: 0.}
  0 $0
  1 $1
  2 $2
  Run

  And actually, I thought my original code was working for me, and then suddenly stopped for no apparent reason. I couldn't reproduce the original, so I figured I my mind was playing tricks on me.

  There might be a subtle compiler bug.

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