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727 :: Empty clause in object variants

• zio_tom78 (orginal) [2015-01-07T00:13:46+01:00] view original

  Hi to everybody,

  It is not clear to me how to declare an empty clause in a object case section:

  type
      Kind = enum
          kNone, kInt, kFloat
      
      value = object
          case k : Kind
          of kNone: # None here
          of kInt: intVal : int
          of kFloat: floatVal : float
  Run

  This produces the error:

  
  test.nim(8, 10) Error: identifier expected, but found 'keyword of'
  Run

  If I put a discard after of true:, I get this error:

  
  test.nim(7, 25) Error: identifier expected, but found 'keyword discard'
  Run

  What is the correct syntax to use in this case?

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• beardo (orginal) [2015-01-07T00:43:18+01:00] view original

  Hello. Just put 'nil' to declare an empty clause. Like this:

  type
      Kind = enum
          kNone, kInt, kFloat
      
      value = object
          case k : Kind
          of kNone: nil
          of kInt: intVal : int
          of kFloat: floatVal : float
  Run

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• Varriount (orginal) [2015-01-07T09:03:03+01:00] view original

  Hrm, I think that's an issue that needs to be fixed. For the rest of the language, using nil for empty clauses was deprecated in favor of 'discard'. It's even worse now, since using nil is inconsistent with the rest of the language.

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• gokr (orginal) [2015-01-08T00:17:39+01:00] view original

  I stumbled at this one too. I clearly agree that "nil" is very unintuitive.

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• zio_tom78 (orginal) [2015-01-08T10:17:02+01:00] view original

  Thanks for the help! I was thinking of adding this information in the Nim manual and send a PR, but perhaps it is better for me to wait for the matter to be settled? (I would favor the usage of discard, as it would be analogous to the control-flow case statement: in fact, this was my first attempt when I tried to compile the code above).

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• Araq (orginal) [2015-01-08T10:18:20+01:00] view original

  We will support discard. It's just an oversight that this hasn't been done already.

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