Thanks for reminding me of the term "stable sort". It was a contrived example. I suppose I could have abstracted even more: Algorithm B sometimes fails on the

Thanks for reminding me of the term "stable sort". It was a contrived example. I suppose I could have abstracted even more: Algorithm B sometimes fails on the output of Algorithm A. We can fix the issue by making B deal with that case, or we can change A so it never produces that output. Sometimes changing the algorithm in A just makes the problem go away, and maybe that was a good idea anyway. This seems too abstract, so I picked a slightly more specific (sorting) thing for A.