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8673 :: Dynamic usage of arithmetic operators in nim

• cobbycobby (orginal) [2021-12-02T20:52:56+01:00] view original

  Hi guys

  I am looking for a way to write code in nim that behaves similar to this Python piece

  In [1]: import operator
  
  In [2]: d = {'*': operator.mul, '+': operator.add}
  
  In [3]: op = '+'
  
  In [4]: d[op](2, 3)
  Out[4]: 5
  
  The problem is that I do not understand how I can store reference to an operator in a Table

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• DavideGalilei (orginal) [2021-12-02T20:56:31+01:00] view original

  Here's an example on how you can do this using a table of procs: https://play.nim-lang.org/#ix=3GOe

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• treeform (orginal) [2021-12-02T20:59:01+01:00] view original

  Nim does not have "operator" module but you can quickly create your own little closure functions that use the operator. Looks nearly identical to python then:

  import tables
  
  let d = {
    '*': proc(a, b: int): int = a * b,
    '+': proc(a, b: int): int = a + b
  }.toTable()
  
  let op = '+'
  
  echo d[op](2, 3)
  Run

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• xigoi (orginal) [2021-12-02T21:33:43+01:00] view original

  I think it would be interesting to have a convenient way to get a specific overload of a procedure. It feels weird to write things like arr.mapIt(frobnicate(it)).

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• DeletedUser (orginal) [2021-12-02T22:06:25+01:00] view original

  The problem isn't that it's overloaded. + is a "magic" proc, it generates different inline code per backend, so it's not a real function. Overloads, including generic overloads, work:

  import sequtils
  
  proc foo[T](x: T): int = x + 1
  proc foo[T: bool](x: T): int = -1
  
  echo @[1, 2, 3].map(foo)
  Run

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