This file is deprecated, for a tree on list, use
Mergesort.v.
A development of Treesort on Heap trees. It has an average
complexity of O(n.log n) but of O(n²) in the worst case (e.g. if
the list is already sorted)
From trees to multisets
contents of a tree as a multiset
Nota Bene : In what follows the definition of SingletonBag
in not used. Actually, we could just take as postulate:
Parameter SingletonBag : A->multiset.