module
data Allows comparision of values for equality. Declare and pass a witness for custom equality.
In contrast to the default equality operator ==, you can define custom equality.
If you explicitly want the strict behavior, pick the strict witness.
equal lhs, rhs
func negated witness
Negates the result of the given Equatable.
func pullback transform, witness
Transforms the inputs of an Equatable-witness.
cmp.pullback { person => person.name }, insensitiveEquatable, Person "Somebody"