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5198 :: How to create a proc from an object?

• hugogranstrom (orginal) [2019-09-16T22:20:04+02:00] view original

  I have a Spline (interpolation) type:

  type
    Spline*[T] = ref object
      x: seq[float]
      coeffs: seq[tuple[float, float, T, T]]
  Run

  And I can evaluate it at a point t using:

  eval*[T](spline: Spline[T], t: float): T
  Run

  What I would like to do, is to create a proc for a specific spline so that I can call it without having to supply the Spline. Something like this:

  var spline = newSpline(x, y)
  # Current way to evaluate it:
  echo spline.eval(2.5)
  
  # How I would like it:
  var f = Spline2Proc(spline) # this is just a placeholder for the magic I want.
  echo f(2.5)
  Run

  The reason for this is that I want to be able to pass a Spline as a proc to for example a proc that does numerical integration of a function.

  Is this possible to do in Nim (without too much troubles)?

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• LeuGim (orginal) [2019-09-16T23:03:42+02:00] view original

  proc Spline2Proc[T](spline: Spline[T]): proc(t: float): T = (proc(t: float): T = eval(spline, t))

  Run

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• hugogranstrom (orginal) [2019-09-17T08:05:14+02:00] view original

  Aaahhhh makes total sense :) this is what's called a closure?

  Thank you very much @LeuGim :-D

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• mratsim (orginal) [2019-09-17T17:45:21+02:00] view original

  yes it's a closure

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