scala, Passing an operator as argument of a function

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说谎
说谎 2021-02-20 08:06

I have this code:

for( i <- 0 to 8){
  ((numbers(i) - i)/3).abs + ((numbers(i) - i)%3).abs
}

and I would like to do, as the title says, some

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  • 2021-02-20 08:17

    First, you need to correctly define op as a function (specifically, a Function2)

    def operate(a: Int, b: Int, op: (Int, Int) => Int ) : Int = (op ((a - b), 3)).abs

    Operators in Scala are actually methods: + is a method of Int(and Long, Double, ...) in Scala OO foundation. Then, to pass a operator (method) as a function, you can lift it using the underscore notation: operate(5, 3, _ + _)

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  • 2021-02-20 08:33

    To get rid of the underscores you need to define the functions as values.

    val / = (a:Int, b: Int) => a / b
    val % = (a:Int, b: Int) => a % b
    
    def by3(a: Int, b: Int, fn: (Int, Int) => Int): Int = fn(a - b, 3).abs
    
    (0 to 8).foreach(i => by3(numbers(i), i, /) + by3(numbers(i), i, %))
    
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  • 2021-02-20 08:37

    Edited/Update:

    Being concise, the shortest way to do it is:

    def doStuff(a: Int, b: Int, op: (Int, Int) => Int) = {op(a - b, 3).abs}

    doStuff(4,1,_%_)

    So you can doStuff(numbers(i), i, _ / _) + doStuff(numbers(i), i, _ % _)

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