How to customize ternary operators in Swift

Question

I know how to customize binary operators, like this

infix operator ** { associativity left precedence 170 }
func ** (left: Double, right: Double) -> Doubl         


        

Answer 1

Here is how you can do it in Swift 4:

precedencegroup SecondaryTernaryPrecedence {
    associativity: right
    higherThan: TernaryPrecedence
    lowerThan: LogicalDisjunctionPrecedence
}

infix operator ~ : SecondaryTernaryPrecedence

func ~ (lhs: @autoclosure () -> Bool, rhs: @escaping @autoclosure () -> T) -> (Bool, () -> T) {
    return (lhs(), rhs)
}

infix operator >< : TernaryPrecedence

@discardableResult func >< (lhs: (Bool, () -> T), rhs: @escaping @autoclosure () -> T) -> T {
    if lhs.0 {
        return lhs.1()
    } else {
        return rhs()
    }
}

Usage

let n = false ~ "it was true" >< "it was false" //"it was false"

true ~ print("it was true") >< print("it was false")
// Prints "it was true"

Note: While this is not a true ternary operator per se, as it uses two infix operators in conjunction with one another, it does in fact somewhat emulate its behaviour when the two operators are used together in the fashion presented above.