val set_eq : MathQL.result -> MathQL.result -> MathQL.result
val set_union : 'a list -> 'a list -> 'a list
-(*
-val set_intersect : 'a list -> 'a list -> 'a list
-*)
+
+val mql_subj : MathQL.value -> MathQL.result
+
val mql_union : ('a * 'b list) list -> ('a * 'b list) list ->
('a * 'b list) list