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9497 :: How to properly typecheck a variable number of array args?

• errata-c (orginal) [2022-09-28T22:58:38+02:00] view original

  I have a statically sized array, and I want to create a constructor proc for it that accepts a list of other (statically sized) arrays. The sum of the sizes of the input arrays must then equal the size of the array being constructed. I know that the information necessary to check this should be available at compile time, but I don't know how to actually implement this in nim. I'm very new to nim in general so I don't have a good idea of were to start with this. I've already tried to do it in a c++ style by making recursive procs that peel one argument off of the varargs at a time, but I don't know how to properly use varargs apparently.

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• auxym (orginal) [2022-09-28T23:36:59+02:00] view original

  proc staticLengthCheck[A, B: static[int]](a: array[A, int], b: array[B, int]): array[4, int] =
    static:
      assert A + B == 4
    
    discard # do stuff here
  
  discard staticLengthCheck([1], [1, 2, 3])  # ok
  discard staticLengthCheck([1, 2], [1, 2, 3]) # compile time assertion error
  Run

  Feel free to use {.error.} insert of assert if you want to provide a customized error message.

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