func removeAll<C : RangeReplaceableCollectionType>(inout: C, keepCapacity: Bool) Remove all elements from x Invalidates all indices with respect to x. keepCapacity, if true, is a non-binding request to avoid releasing storage, which can be a useful optimization when x is going to be grown again. Complexity: O(count(x)). Declaration func removeAll<C : RangeReplaceableCollectionType>(inout x: C, keepCapacity: Bool = default)