A type constraint specifies that a generic type must inherit from a specific class or conform to a particular protocol. This allows us to use the methods or properties defined by the parent class or protocol with the generic types. Let's look at how to use type constraints by rewriting the genericEqual() function to use the Comparable protocol:
func testGenericComparable<T: Comparable>(a: T, b: T) -> Bool {
return a == b
}
To specify the type constraint, we put the type or protocol constraint after the generic placeholder, thus separating the generic placeholder and the constraint with a colon. This new function works in ways that we might expect it to, and it will compare the values of the two parameters and return true if they are equal, or false if they are not.
We can declare multiple constraints, just like we can declare...