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9465 :: One lookup table indexed by multiple enums

• KerryC (orginal) [2022-09-14T07:28:39+02:00] view original

  I have some enum types which I am using to access values from lookup tables. I thought for instances where the values would be the same for each enum that I might be able to do this:

  
  type
    aEnum = enum A1, A2, A3
    bEnum = enum B1, B2, B3
    eitherEnum = aEnum | bEnum
  
  let  lookup: array[eitherEnum, int] = [1, 2, 3]
  Run

  But it fails and returns Error: ordinal type expected. Is there anyway other than defining the lookup table for each enum separately?

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• ElegantBeef (orginal) [2022-09-14T07:36:01+02:00] view original

  The easiest way to do this would be to make a procedure that does the look up as such:

  type
    aEnum = enum A1, A2, A3
    bEnum = enum B1, B2, B3
  
  let lookupArr = [1, 2, 3]
  proc lookup*(enm: aEnum or bEnum): int = lookupArr[ord enm]
  
  for i in 0..2:
    assert lookup(aEnum(i)) == lookup(bEnum(i))
  Run

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• KerryC (orginal) [2022-09-14T07:48:36+02:00] view original

  Ah great! That is actually what I was trying to do before stripping things down to a minimal example but I failed to realize that I needed the ord in order for enm to work as an index. Thanks a lot!

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