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2238 :: Closures/Value capture

• sam (orginal) [2016-04-30T07:45:55+02:00] view original

  I read it from rosettacode:

  var funcs: seq[proc(): int] = @[]
  
  for i in 0..9:
    let x = i
    funcs.add(proc (): int = x * x)
  
  for i in 0..8:
    echo "func[", i, "]: ", funcs[i]()
  Run

  but the output very odd

  
  func[0]: 81
  func[1]: 81
  func[2]: 81
  func[3]: 81
  func[4]: 81
  func[5]: 81
  func[6]: 81
  func[7]: 81
  func[8]: 81
  Run

  how to fix that?

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• Arrrrrrrrr (orginal) [2016-04-30T09:41:01+02:00] view original

  It changed in the last major release http://nim-lang.org/news.html#Z2016-01-18-version-0-13-0-released

  var funcs: seq[proc(): int] = @[]
  
  for i in 0..9:
    (proc() =
      let x = i
      funcs.add(proc (): int = x * x))()
  
  for i in 0..8:
    echo "func[", i, "]: ", funcs[i]()
  Run

  You can ease the pain using templates (Run It):

  template loopClosure(body: untyped) =
    block:
      proc lc = body
      lc()
  
  [...]
  
  for i in 0..9:
    loopClosure:
      let x = i
      add funcs, proc: int = x * x
  Run

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• sam (orginal) [2016-05-01T05:25:29+02:00] view original

  You can ease the pain using templates

  thanks. good idea.

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