Make only one copy of the data

[make-github-pseudonymous-again]

Since we do not deep copy values and since we do not expose copies this makes no difference. Would suffice to keep track of indices for each copy in a single buffer, when all indices > 0 we can shift the deque left and decrease all counters. To make this check efficient we can use a +1/-1 heap.

[make-github-pseudonymous-again]

Note that this would in almost all cases use less space, and be considerably more efficient in the case where we have a a few copies where one of them gets read much more than the others.

PS: Having one copy read much more than the others is what happens when using product([infiniteIterable], 10).

[make-github-pseudonymous-again]

Use a singly linked list instead.

[make-github-pseudonymous-again]

If implementing this, test the following:

• An item is only pulled from the source iterable if it is accessed at least once
• A pulled item can be garbage collected as soon as it has been pulled in all copies and the consumer has lost all references to it (cannot really check this?)