ghc-equivalence 0.3.5 Maintaining an equivalence relation implemented as union-find

This is an implementation of Tarjan's Union-Find algorithm (Robert E.: Tarjan. "Efficiency of a Good But Not Linear Set Union Algorithm",JACM 22(2), 1975) in order to maintain an equivalence relation. This implementation is a port of the union-find package using the ST monad transformer (instead of the IO monad).