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7325 :: Own numeric type

• micunek (orginal) [2021-01-02T22:08:50+01:00] view original

  Hi All,

  Could someone pls. help me with this: I would like to create own numeric type which consists for example only from these numbers "0,1,3,6,8,9".

  I was successful with range:

  type my_num_type = range[0..9]

  However I do not want to have 2,4,5,7 there.

  Thanks Peter

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• lqdev (orginal) [2021-01-02T23:52:02+01:00] view original

  That's not a language feature, possibly due to the low number of actual use cases for it.

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• Zoom (orginal) [2021-01-03T02:43:15+01:00] view original

  The point of having a numerical type is to have the ability to perform mathematical operations, but in case of a restricted set of numbers most of the time you'll be getting answers outside of the set, so you still need to perform checks afterwards. So either you just use the regular numbers and pretend all other don't exist, while validating what you have after each operation, or you use an enum and implement the required operations by hand.

  Can't imagine any use-case at a go, though.

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• cantanima (orginal) [2021-01-03T05:22:14+01:00] view original

  Do you have some unusual arithmetic going on here? in that case you might want to define a class, and/or use an enumeration.

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• snej (orginal) [2021-01-03T05:44:00+01:00] view original

  Sounds like you want an enum, with those integers assigned to the values.

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• micunek (orginal) [2021-01-03T09:43:09+01:00] view original

  yes, you are right. I just thought to use something as enum for SMPP protocol defined values for example for NPI (Numbering Plan Indicator)

  npi_type = enum

  UNKNOWN = 0x00 ISDN = 0x01 DATA = 0x03 TELEX = 0x04 LAND_MOB = 0x06 NATIONAL = 0x08 PRIVATE = 0x09 ERMES = 0x0A IP = 0x0E WAP = 0x12

  I do not really need "names". Of course I can get num value by ord() function but it is not appropriate. There is no arithmetic just small set of numbers. I checked some go-lang implementation and they use uint8 so it seems I use it also for NIM implementation.

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• snej (orginal) [2021-01-06T00:16:07+01:00] view original

  Why do you want to use the numbers instead of names? The names are much easier to recognize and remember.

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• JohnAD (orginal) [2021-01-06T20:16:37+01:00] view original

  There are many ways to do it. Perhaps something like:

  # a data type called Example
  type
    ExampleDigits = enum
      ed0 = 0,
      ed1 = 1,
      ed2 = 3,
      ed6 = 6,
      ed8 = 8,
      ed9 = 9
  
  type
    Example = object
      characteristic = seq[MyDigits]
      mantissa = seq[MyDigits]
  
  proc newExample(string): Example =
     # do stuff here
  
  proc toFloat(Example): float =
     # do stuff
  
  assert newExample("812.6").toFloat == 322.3  # or whatever 812.6 should equal :)
  Run

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