In `Iterable.reduce`, why is `T` constrained to be...

# announcements

[nickk]

In Iterable.reduce, why is T constrained to be a subtype of S?
As long as operation produces the correct type, what is the problem?

public inline fun <S, T : S> Iterable<T>.reduce(operation: (acc: S, T) -> S): S

[diesieben07]

The initial value of acc is the first element, so the elements of the Iterable need to fit into S.

[spand]

You want fold