Hello,

I just pushed on https://github.com/craff/block_sort.git an old piece of code: a
stable sorting algorithm which is in O(n ln k) where n is the size of the list
and k the number of changes of direction.  It is often much faster than
List.sort, on my tests, never more than 10% slower.  The tests are available on
github.

If people are interested I could provide a version for arrays.

A challenge would be to provide a O(n ln k) sorting on list that is always
faster than List.sort. Any ideas ?

Cheers,
Christophe