>> […]
>> Set conforming to Collection is even worse than just conforming to Sequence
>> as a quote from the documentation shows: "In addition to the operations that
>> collections inherit from the Sequence protocol, you gain access to methods
>> that depend on accessing an element at a specific position in a collection."
>> Clearly the elements of a Set do not have specific positions.
>>
>
> That’s not at all clear to me, could you elaborate? My understanding is that
> elements of Set definitely *do* have a position, and that’s why you can use
> an index on a set to retrieve the element. The same index on the same set
> retrieves the same element.
A Set only has "indices" because it confirms to a protocol where almost all the
requirements are meaningless for an unordered collection. Or at best, for the
same reason it has an "order": as a side-effect of the fact that it can be
iterated over, you can give indices for each element on a specific iteration;
those indices are meaningless for the set itself, and should not be used for
anything but a full, order-independent iteration.
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