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6675 :: problem with {.borrow.}

• mungosyme (orginal) [2020-08-13T10:29:36+02:00] view original

  Hi, I am new to nim and would be grateful if someone can help me with this -

  (I have changed the back ticks around the operators to single quotes in order to be able to post here)

  type

  Temp* = distinct int

  proc '+'* (A, B: Temp): Temp {.borrow}

  proc '<'* (A, B: Temp): bool {.borrow.}

  proc '<='* (A, B: Temp): bool {.borrow.}

  proc '=='* (A, B: Temp): bool {.borrow}

  works fine but both

  proc '>'* (A, B: Temp): bool {.borrow.}

  and

  proc '>='* (A, B: Temp): bool {.borrow.}

  fail !

  Many thanks

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• mratsim (orginal) [2020-08-13T11:45:07+02:00] view original

  > and >= are catch-all templates defined in system.nim, see

  https://nim-lang.org/docs/system.html#%3E%3D.t%2Cuntyped%2Cuntyped

  A > B just does B < A, there is no need to borrow them (and you can't).

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• mungosyme (orginal) [2020-08-13T17:45:31+02:00] view original

  Thanks mratsim, that makes sense. Without being picky, why does

  type

  Temp* {.borrow: '>' .} = distinct int

  work if > cannot be borrowed ? To be consistent that should also fail.

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• jibal (orginal) [2020-08-13T20:49:49+02:00] view original

  No, that says that '>' is defined for your Temp type. That has nothing to do with the fact that '>' is implemented as '<' with args reversed, which you can't change.

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• cumulonimbus (orginal) [2020-08-14T16:07:18+02:00] view original

  A > B just does B < A, there is no need to borrow them (and you can't).

  That's wrong for float NaNs and any similar system, such as SQL's 3-valued logic. I didn't notice this before .. but I think this is something that should be more prominently documented; or am I wrong?

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