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2248 :: SOme questions with iterators and for loops

• vasya_t (orginal) [2016-05-06T00:57:21+02:00] view original

  1. Why for loops use implicit call of pairs? Isn't using explicit pairs call with possibility of tuple unpacking more obvious and scalable?

  2. Is there any way to iterate multiple collections simultaneously, like with python:

  for x, y in zip(xs, ys):
      ...
  Run

  As far as I know, there is no zip analog in standard library. How can I implement it myself?

  3. Are there any plans to adding tuple unpacking for for loops? I think, it's reasonable to have it in variable definition in for loops as you already have it in variable definition in let and var.
  4. Why does functional stuff like sequtils.filter or math.sum operate on sequences? Isn't it more convenient and reasonable to operate on iterators?

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• Arrrrrrrrr (orginal) [2016-05-06T10:02:13+02:00] view original

  2. <http://nim-lang.org/docs/sequtils.html#zip,seq[S],seq[T]>
  3. You can using items (Run it):

  let s = @[(1, false, "abc"), (2, true, "def")]
  for num, bo, str in items(s):
    echo num, ' ', bo, ' ', str
  Run

  4. Not sure why, but you can do more things with seqs than with iterators (and getting an iterator from seq is a no brain). Also (Don't quote me on this) i think there are some optimizations that may remove the allocation on heap under certain circustances. But i'm not sure and i dont want to spread myths.

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• OderWat (orginal) [2016-05-06T12:17:31+02:00] view original

  You may want to look at https://github.com/petermora/nimLazy

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• Krux02 (orginal) [2016-05-08T23:11:04+02:00] view original

  actually, this code works for your example:

  iterator zip[A,B](a:seq[A], b:seq[B]) : tuple[a:A,b:B] =
    for i in 0 .. min(len(a), len(b))-1:
      yield (a[i], b[i])
  
  let
    xs = @[1,2,3,4]
    ys = @["a", "b", "c", "d"]
  
  
  for x,y in zip(xs,ys):
    echo x, y
  
  Run

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