which one would expect to cause sort to go into an infinite loop

Not this "one". And the documentation is pretty clear that this can't happen:

In 5.7, the quicksort implementation was replaced with a stable mergesort algorithm whose worst-case behavior is O(NlogN).

An infinite loops is a way worse case than O(NlogN).

And, no, I'm pretty sure that the following bit in the documentation doesn't trump that part:

If it returns inconsistent results (sometimes saying $x[1] is less than $x[2] and sometimes saying the opposite, for example) the results are not well-defined.

"Not well-defined" means that you might not be able to predict the order in which the items are returned. All of the items will be returned, one alias each, and in under O(NlogN) "time". It is just their precise order that is not well-defined.

- tye        

In reply to Re: Sort mechanics problems with objects and potentially contradicting comparisons (can't cause infinite loop) by tye
in thread Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) by anonymized user 468275

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