clamp() in Swift

Clamp.swift

///Returns the input value clamped to the lower and upper limits.
func clamp<T: Comparable>(value: T, lower: T, upper: T) -> T {
	return min(max(value, lower), upper)
}


//-----------------------------------------------
// Example usage

let proposedIndex = 6
let i = clamp(proposedIndex, 0, 5)


// What clamp() replaces
func getIndex(proposedIndex: Int) -> Int {

    if proposedIndex < 0 {
        return 0
    }
    else if proposedIndex <= 5 {
        return proposedIndex
    }
    else {
        return 5
    }
}

Alternative:

extension Comparable
{
    func clamp<T: Comparable>(lower: T, _ upper: T) -> T {
        return min(max(self as! T, lower), upper)
    }
}

Example usage:

let value = 7
let clamped = value.clamp(3, 6)

There is also discussion here http://stackoverflow.com/a/43769799/300224 with a more detailed answer.

To avoid force casting you could do something like that since Self is Comparable

extension Comparable {
  func clamp(lower: Self, upper: Self) -> Self {
    return min(max(self, lower), upper)
  }
}