* http://cs.unibo.it/helm/.
*)
-exception UnificationFailure of string;;
-exception Uncertain of string;;
-exception AssertFailure of string;;
+exception UnificationFailure of string Lazy.t;;
+exception Uncertain of string Lazy.t;;
+exception AssertFailure of string Lazy.t;;
(* fo_unif metasenv context t1 t2 *)
(* unifies [t1] and [t2] in a context [context]. *)