> But if you do this you will get a different compiler error, because your > struct will no longer conform to Sequence, which requires makeIterator to be > non-mutating. This is important, especially assuming your array is eventually > going to conform to Collection as well. One of the requirements of > collections is that they give an accurate count, but in the case of your > array, the count returned might be different (greater) than the number of > elements returned when you actually iterate the array, and this is not > allowed (you may find that some standard library functions will trap when > they discover that this has happened).
Btw, isn’t it strange that the next() method in `IteratorProtocol` *is* mutating, and makeIterator() is not?
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