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4965 :: Sequence of typeclass

• thefoxandflea (orginal) [2019-06-25T02:00:43+02:00] view original

  I would like to do something like the following:

  type Encodable = int | string
  type Encoded = object
    ...
  
  proc encode(i: int): Encoded = ...
  proc encode(s: string): Encoded = ...
  proc encode(l: seq[Encodable]): Encoded = ...
  Run

  This seems to compile fine, however I still cannot do something like:

  let encoded = encode(@[1, "a"])
  Run

  because heterogeneous sequences are not supported. In this scenario, shouldn't the common typeclass "unify" the int and string resulting in a homogenous sequence?

  I know I could use a variant type here, but I would prefer to keep the interface as simple as possible.

  Is there a suggested workaround for this? Maybe a macro is necessary?

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• juancarlospaco (orginal) [2019-06-25T04:56:46+02:00] view original

  https://nim-lang.org/docs/manual.html#types-varargs See the Example 2.

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• leorize (orginal) [2019-06-25T10:24:58+02:00] view original

  Typeclasses in Nim is only used for generics, meaning that they're a compile-time constraint, not a runtime one. You'd need an object variant for this case.

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