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555 :: How to call iterator?

• Cyther606 (orginal) [2014-09-10T23:34:03+02:00] view original

  I was trying to filter a seq1: seq[seq[int]], so that seq1[X][0] would not appear more than once in the resulting seq. I have since figured out how to do this, e.g:

  proc dedup(seq0: seq[seq[int]]): seq[seq[int]] =
    # given seq0, returns seq0 with no more than one occurence of seq[X][0]
    var seq3 = newSeq[seq[int]]()
    proc threadUniqs(seq1: seq[seq[int]], i: int): seq[int] =
      var seq2 = newSeq[seq[int]]()
      seq2.add seq1.filter do (x: seq[int]) -> bool: x[0] == seq1[i][0]
      return seq2[seq2.high]
    for i in 0 .. <seq0.len:
      seq3.add seq0.threadUniqs(i)
    return seq3.deduplicate
  Run

  Why does this iterator fail?

  import sequtils
  
  let thread = @[@[0, 0],
                 @[0, 1],
                 @[2, 2],
                 @[2, 3]]
  
  iterator threadUniqs(seq1: seq[seq[int]]): seq[seq[int]] =
    for i in 0 .. <seq1.len:
      yield seq1.filter do (x: seq[int]) -> bool: x[0] == seq1[i][0]
  
  for uniqs in thread.threadUniqs:
    echo uniqs
  Run

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• will (orginal) [2014-09-11T02:21:30+02:00] view original

  I guess some variables may not be getting lifted into the closure?

  maybe this work around works:

  
  import sequtils
  
  let thread = @[@[0, 0],
                 @[0, 1],
                 @[2, 2],
                 @[2, 3]]
  
  iterator threadUniqs(seq1: seq[seq[int]]): seq[seq[int]] =
    let wrapper = proc (a: seq[seq[int]], index: int): seq[seq[int]] = a.filter do (x: seq[int]) -> bool: x[0] == a[index][0]
    for i in 0 .. <seq1.len:
      yield wrapper(seq1,i)
  
  for uniqs in thread.threadUniqs:
    echo uniqs
  Run

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• Araq (orginal) [2014-09-11T09:14:40+02:00] view original

  Instead of

  
  iterator threadUniqs(seq1: seq[seq[int]]): seq[seq[int]] =
    for i in 0 .. <seq1.len:
      yield seq1.filter do (x: seq[int]) -> bool: x[0] == seq1[i][0]
  Run

  try this:

  
  iterator threadUniqs(seq1: seq[seq[int]]): seq[seq[int]] =
    for i in 0 .. <seq1.len:
      let j = i
      yield seq1.filter do (x: seq[int]) -> bool: x[0] == seq1[j][0]
  Run

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• Cyther606 (orginal) [2014-09-11T17:34:34+02:00] view original

  will's wrapper version seems to work. Araq's code doesn't compile [1]:

  threaduniqs.nim(13, 0) Info: instantiation from here
  threaduniqs.nim(13, 0) Info: instantiation from here
  threaduniqs.nim(10, 8) Error: internal error: transformVarSection
  No stack traceback available
  Run

  [1] on today's devel HEAD (v0.9.4.639), and on earlier devel (v0.9.4.605)

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• Araq (orginal) [2014-09-11T20:10:14+02:00] view original

  I created a bug report: https://github.com/Araq/Nimrod/issues/1527

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