giles 8188a82a58 ocaml: phase 6 List.sort upgraded to mergesort (+3 tests, 528 total) ...

The previous List.sort was O(n^2) insertion sort. Replaced with a
straightforward mergesort:

  split lst    -> alternating-take into ([odd], [even])
  merge xs ys  -> classic two-finger merge under cmp
  sort cmp xs  -> base cases [], [x]; otherwise split + recursive
                  sort on each half + merge

Tuple destructuring on the split result is expressed via nested
match — let-tuple-destructuring would be cleaner but works today.

This benefits sort_uniq (which calls sort first), Set.Make.add via
sort etc., and any user program using List.sort. Stable_sort is
already aliased to sort.

2026-05-09 03:01:28 +00:00

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