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4148 :: Units of measurement and universal zero

• cdome (orginal) [2018-08-22T15:08:09+02:00] view original

  Hi Everyone,

  I am trying to improve units of measurements usability I currently have in Nim.

  Basic idea is if value is compile time zero than it is automatically convertible to other unit of measurement.

  For example, I have the following type definition

  type Kg = distinct float
  Run

  I am trying to write converter that converts 0.0 float to Kg automatically, but only zero. Other values should require explicit conversion. I have tried so far

  converter mykg_conv(x: range[0.0 .. 0.0]{lit} = x.Kg
  Run

  doesn't work, as far as I call tell because 0.0 is range[0.0 .. 0.0] returns false.

  Any clever tricks I can use to achieve much desired effect? Possible I can utilize static[T] in some way?

  Thank you

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• mratsim (orginal) [2018-08-23T08:39:53+02:00] view original

  You can't have selective conversion of run-time values.

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• Araq (orginal) [2018-08-23T08:42:53+02:00] view original

  as far as I call tell because 0.0 is range[0.0 .. 0.0] returns false

  Isn't this a bug worth reporting? :-)

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• cdome (orginal) [2018-08-23T15:03:31+02:00] view original

  Hi Mratsim, I want to convert compile time zeros

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• timothee (orginal) [2018-08-23T15:27:06+02:00] view original

  1 is range[0 .. 2] is also false what's the correct usage?

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• cdome (orginal) [2018-08-23T15:49:33+02:00] view original

  Hi Araq, I can report as a bug no problem. I thought it is natural, because 0.0 is float and float is not range[0.0 .. 0.0]. range[0.0 .. 0.0] is float, but not vice versa. Therefore you need to go beyond type relation to get correct answer in this example.

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• cdome (orginal) [2018-08-23T15:54:37+02:00] view original

  @timothee, see my explanation. If you use only types than the answer you are going to get is false, because to 2 is int. You need to consider actual values to get the right answer.

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• cdome (orginal) [2018-08-23T16:18:55+02:00] view original

  Ah, Actually, TType.n in makes it clear how it can be implement it. Nice... I'll try make a PR instead of bug report.

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• cdome (orginal) [2018-08-23T19:26:37+02:00] view original

  TType.n is nil for zero ;(

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