* http://cs.unibo.it/helm/.
*)
-exception UnificationFailure of string;;
+type failure_msg
+
+exception UnificationFailure of failure_msg;;
exception Uncertain of string;;
-exception AssertFailure of string;;
+exception AssertFailure of failure_msg;;
+
+val failure_msg_of_string: string -> failure_msg
+val explain_error: failure_msg -> string
(* fo_unif metasenv context t1 t2 *)
(* unifies [t1] and [t2] in a context [context]. *)