CODEWITHSUNDEEP
swiftgenericstypes
Woodstock
Woodstock

Reputation: 22926

Can't constrain generic types to be equivalent in Swift 5

Why doesn't Swift allow this generic function:

I'm trying to express a generic function that will take two "number" types, and compare them, could be Ints, Floats, Doubles etc...

Why does Swift say Same-type requirement makes generic parameters 'T' and 'U' equivalent, what's wrong with that?

func isSameNumber <T, U> (lhs: T, rhs: U) where T: Numeric, U:Numeric, T == U {
    if lhs == rhs {
        print("true")
    }
    else{
        print("false")
    }
}

Upvotes: 1

Views: 378

Answers (1)

David Pasztor
David Pasztor

Reputation: 54706

If T == U, then you only have a single generic type, so don't declare 2 generic types. You simply need to constraint both input arguments to the same generic type, T.

func isSameNumber<T>(lhs: T, rhs: T) where T: Numeric {
    if lhs == rhs {
        print("true")
    }
    else{
        print("false")
    }
}

Upvotes: 5

Related Questions