> Le 22 mai 2016 à 03:07, Adam Nemecek via swift-evolution
> <swift-evolution@swift.org> a écrit :
>
> Howdy,
> I think that the SignedNumberType should implement a method called sign that
> will return -1 for negative numbers, 0 for 0 and 1 for positive numbers. This
> is similar to the signum method in e.g. Java and similarly called methods in
> other languages.
>
> The implementation is fairly straight forward
>
> extension SignedNumberType {
> var sign: Self {
> if self == 0 {
> return 0
> }
> else if self > 0 {
> return 1
> }
> return -1
> }
> }
>
> I was trying to implement is without branching by doing (x > 0) - (x < 0) but
> I couldn't get the types right so I'm open to suggestions.
>
Challenge accepted… Removed the if/else if, at the cost of double function call
to a tri-op:
extension Bool {
func as01<T:SignedNumberType>() -> T { return self ? 1 : 0 }
}
extension SignedNumberType {
var sign: Self { return (self > 0).as01() - (self < 0).as01() }
}
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