Hi,

> My team just noticed that the behavior of Map.fold changed in OCaml 
> version 3.08.4.

a program of mine suffers a lot from this change. In fact 
my boss found today a remaining hidden bug related to this change :-(

What about to provide a "fold_left" (= new version) and "fold_right" 
(= old version)? Fixing old programs would be simple. Combined with 
exceptions there would be a fast solution (O(1) instead of O(n)) 
to find a minimum and maximum key from a large map.

Christoph Bauer