Swift: generic power function as infix operator

Question

Below is the answer to the original question of how to add a power operator for Int numbers:

infix operator ^^ { associativity left precedence 160 }
func ^^ (radix: Int, power: Int) -> Int {
    return Int(pow(CGFloat(radix), CGFloat(power)))
}

How would one generalise this so that it works for Double, Float, and Int?

matt · Accepted Answer · 2015-07-16T21:51:18.257

0

You cannot "generalize" it. You have to implement it for each type separately.

If you look in the Swift header, you will see that that is exactly what Swift itself does for the built-in operators such as +. There is no "general" + function; there is one + function for every numeric type.

Thus:

infix operator ^^ { associativity left precedence 160 }
func ^^ (radix: Int, power: Int) -> Int {
    return Int(pow(CGFloat(radix), CGFloat(power)))
}
func ^^ (radix: Double, power: Double) -> Double {
    return Double(pow(CGFloat(radix), CGFloat(power)))
}
// ... and so on for as many types as you like ...

edited Jul 16 '15 at 21:51

answered Jul 16 '15 at 21:39

matt

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But if I copy the code and replace all `Int` with `Double`, I get a compiler error "operator redeclared" – fiship Jul 16 '15 at 21:42
@fiship you might find the `pow` function useful for `Double` and the like – Matteo Piombo Jul 16 '15 at 21:47
1

Oh, I should have mentioned - you declare the `operator` once but the `func` many times. – matt Jul 16 '15 at 21:50
@fiship Consider that if you just substitute `Int` with `Double` you are squeezing doubles into cgfloat ... it might lead to some nasty bugs. – Matteo Piombo Jul 16 '15 at 21:54
Ah, thanks! I was missing this bit of how to connect the `func` and the `operator` like that – fiship Jul 16 '15 at 22:03

Swift: generic power function as infix operator

1 Answers1