Why does `fun <S, T : S> Iterable<T>.r...

# getting-started

[Lukasz Kalnik]

Why does fun <S, T : S> Iterable<T>.reduce(operation: (acc: S, T) -> S): S have two generic type parameters (S and T) when it operates on the same collection? In its source code acc is taken from the Iterable<T> so S is always the same type as T anyway.

[Lukasz Kalnik]

Ok, I see, T : S, so S can be a supertype of T.