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958 :: Modify loop variable

• axben (orginal) [2015-03-03T10:31:06+01:00] view original

  Is there any possibility to modify a loop variable from within the loop?

  E.g.

  for i in 0..5:
     if i == 2:
        inc i
  Run

  Although this is probably not envisioned, it would be easier to read than:

  var i = 0
  while i <= 5
     if i == 2:
        inc i
     inc i
  Run

  especially it the loop contained conditional break s or continue s.

  An alternative would be using an external variable for the loop's control like:

  var i: int
  for i in 0..5:
     if i == 2:
        inc i
  Run

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• Araq (orginal) [2015-03-03T12:16:12+01:00] view original

  Although this is probably not envisioned, it would be easier to read than ...

  No, it wouldn't. If you have unstructured iteration, it's nice to see that immediately thanks to the 'while'.

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• yglukhov (orginal) [2015-03-03T19:58:50+01:00] view original

  What about iterating over array and modifying it?

  var arr : array[10, int] = ...
  for v in arr:
      v = 123
  Run

  Would be a lot of use for arrays of aggregates. Is this somehow possible?

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• def (orginal) [2015-03-03T20:08:22+01:00] view original

  Would be a lot of use for arrays of aggregates. Is this somehow possible?

  If you get the devel branch of Nim, it is indeed!:

  var arr: array[10, int]
  
  for v in arr.mitems:
    v = 123
  Run

  There is mpairs as well for for i, v in arr.mpairs: ...

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• yglukhov (orginal) [2015-03-03T20:11:49+01:00] view original

  So that is what that cryptic mitems means!! :D I'm on devel, but never thought that's what I need. Thanx!

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• pdw (orginal) [2015-03-04T04:02:32+01:00] view original

  arr.varItems would seem a good bit clearer (assuming it gives var).

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