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9147 :: Var + varargs = 🤯

• archnim (orginal) [2022-05-07T21:09:54+02:00] view original

  Hello world. Please, what is wrong with my code ?

  var
    i1 = 1
    i2 = 2
    i3 = 3
  
  proc show(i: var int) = echo i # A proc that needs var
  
  proc myProc(ii: var varargs[int]) =
    for i in mitems ii:
      show i
  
  myProc(i1, i2, i3);
  Run

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• xigoi (orginal) [2022-05-07T21:29:27+02:00] view original

  Interestingly, if you do ii: varargs[var int] instead, it will accept the arguments, but won't allow you to mutate the array. This should probably be changed.

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• archnim (orginal) [2022-05-07T21:35:33+02:00] view original

  With varargs[var int], I get:

  
  Error: invalid type: 'var int' in this context: 'proc (ii: varargs[var int])' for proc
  Run

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• ElegantBeef (orginal) [2022-05-07T21:45:24+02:00] view original

  The way varargs works prevents it from being mutable, if you pass in i1, i2, i3 it implicitly creates an array of [i1, i2, i3] which means it's an immutable data type. You should probably use an array and take var openArray[int] instead of i1, i2, i3. In present Nim I do not think varargs can represent what you're after. Though I could be wrong.

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• archnim (orginal) [2022-05-07T21:46:39+02:00] view original

  Thank you.

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• ElegantBeef (orginal) [2022-05-07T22:34:44+02:00] view original

  Well view types should allow it to happen, but until then you can either do the open array or use a macro like:

  import std/macros
  
  macro myPretendProc(ii: varargs[var int]): untyped =
    result = newStmtList()
    for x in ii:
      result.add newCall("show", x)
  
  var
    i1 = 1
    i2 = 2
    i3 = 3
  
  proc show(i: var int) = echo i # A proc that needs var
  
  myPretendProc(i1, i2, i3);
  Run

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