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7077 :: What does this expression mean?

• linwaytin (orginal) [2020-11-11T23:32:32+01:00] view original

  Hi community,

  I'm new to Nim and try to learn the basics from Exercism.
  In the exercise React, I need to implement a spreadsheet-like function.
  

  This exercise has little information and thus I have to figure out the structure of the code from the test suite as follows.

  suite "React":
    test "setting the value of an input cell changes the observable value":
      let
        reactor = newReactor()
        i1 = reactor.createInput(1)
      check i1.value == 1
      i1.value = 2
      check i1.value == 2
    
    test "the value of a compute is determined by the value of the dependencies":
      let
        reactor = newReactor()
        i1 = reactor.createInput(1)
        # Using @[Cell i1] to avoid the compiler inferring the array type as seq[InputCell],
        # which is incompatible with seq[Cell].
        c1 = reactor.createCompute(@[Cell i1], proc(vals: seq[int]): int = vals[0] + 1)
      check c1.value == 2
      i1.value = 2
      check c1.value == 3
  Run

  I have no idea of what @[Cell i1], mentioned in the comment, means.
  Does anybody have some idea?
  

  Thank you.

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• pietroppeter (orginal) [2020-11-12T01:11:51+01:00] view original

  There are probably two types Cell and InputCell. i1 as returned by createInput is of type InputCell. createCompute needs a seq[Cell] as second argument. Cell i1 is an explicit conversion of type from InputCell to Cell.

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• linwaytin (orginal) [2020-11-12T02:47:01+01:00] view original

  Thank you. I never thought it is a conversion. That looks reasonable.

  Do I need to write the conversion function by myself? Or, if there is an relation like inheritance between Cell and InputCell, the conversion is automatically generated?

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