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505 :: critbits: "Error: for a 'var' type a variable needs to be passed"

• sjakobi (orginal) [2014-07-21T07:36:30+02:00] view original

  The following code returns an error that I don't quite know how to handle:

  
  import critbits
  
  proc `==`[T](a, b: TCritBitTree[T]): bool =
    if a.len != b.len:
      return
    for key, val in a:
      if b[key] != val:
        return
    return true
  
  when isMainModule:
    var x, y: TCritBitTree[int]
    assert(x == y)
  Run

  The error message:

  
  > nimrod c -r --verbosity=0 *_test.nim
  lib/nimrod/pure/collections/critbits.nim(122, 6) Hint: 'n' is declared but not used [XDeclaredButNotUsed]
  word_count_test.nim(13, 11) Info: instantiation from here
  word_count_test.nim(7, 7) Error: for a 'var' type a variable needs to be passed
  Run

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• sjakobi (orginal) [2014-07-21T07:41:05+02:00] view original

  Uh, I figured it out myself: I need to pass a and b as var TCritBitTree[T].

  But can somebody explain why this is necessary? I clearly don't want to change a or b. (The error message could be improved too…)

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• Araq (orginal) [2014-07-21T09:52:49+02:00] view original

  For some reason the header of [] is declared as:

  
  
  proc `[]`*[T](c: var TCritBitTree[T], key: string): T {.inline.}
  Run

  Which is wrong. Please fill in a bug report.

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