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196 :: Can object variants share data?

• enurlyx (orginal) [2013-08-06T12:48:03+02:00] view original

  Hello,

  i am playing with nimrod and got some question about object variants.

  1. Will every variable be created in memory, even i am not allowed to access it?
  2. Is there a way to create a variant that shares a variable with an other variant? Like in the following example, a will have var1 and b will have var1 and var2.

  type
    Node = object
      case kind: NodeKind
      of NodeKind.a, NodeKind.b:
        var1: float
      of NodeKind.b:
        var2: float
  Run

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• Araq (orginal) [2013-08-06T14:02:20+02:00] view original

  No but you can do this:

  
  type
    Node = object
      var1: float
      case kind: NodeKind
      of NodeKind.b:
        var2: float
      else: nil
  Run

  The implementation compiles it to a C union.

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• enurlyx (orginal) [2013-08-06T19:14:25+02:00] view original

  Thank you for reply.

  For my example it works this way. Now if I build something like a double linked list I would like to use the feature in the following way (middle will have next and prev):

  type
    NodePtr = ref Node
    Node = object
      case kind: NodeKind
      of start, middle:
        next: NodePtr
      of end, middle:
        prev: NodePtr
  Run

  As I understand that is currently not possible. Would it make sense to extend the compiler to support this kind of construction? It seems to be usefull.

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• Araq (orginal) [2013-08-08T19:57:58+02:00] view original

  Yes it's useful. However I don't think it will be implemented before 1.0.0 is released.

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