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11304 :: Access operator on distinct type of array

• lollinux (orginal) [2024-03-27T12:43:14+01:00] view original

  type
      ## Define a generic vector type with a fixed size and element type.
      Vec[N: static[int], V] = array[N, V]
  
  
  echo `[]`(array[3, float]([1.0, 2.0, 3.0]), 1) # 2.0
  echo `[]`(Vec[3, float]([1.0, 2.0, 3.0]), 1) # 2.0
  Run

  This code works fine, but when I define some distinct type of Vec[N, V] and borrow the base access operator I get this error: "no symbol to borrow from found".

  type Color = distinct Vec[3, float]
  proc `[]`(a: Color, i: int): float {.borrow.}
  Run

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• Clonk (orginal) [2024-03-27T16:36:45+01:00] view original

  I think this is because [] is not a normal proc but a magic proc : https://github.com/nim-lang/Nim/blob/c934d5986d241c2a34c89ae3c16047299fd3a86b/lib/system.nim#L354

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• xigoi (orginal) [2024-03-29T12:07:14+01:00] view original

  But why does {.borrow.} not work with magic procs?

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• sls1005 (orginal) [2024-03-29T14:02:31+01:00] view original

  I don't think so. A large part of procs in the system module, including +, - and * for int, are {.magic.}, and we have no problem borrowing them. I think the problem is that it is a generic proc, so the signature didn't match.

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