+type 'a clause =
+ int
+ * ('a literal * bool) list (* left hand side of the arrow,
+ with flag for selection *)
+ * ('a literal * bool) list (* right hand side of the arrow,
+ with flag for selection *)
+ * varlist
+ * 'a proof
+
+type 'a passive_clause = int * 'a clause (* weight * equation *)
+
+
+let vars_of_term ?(start_acc=[]) t =
+ let rec aux acc = function
+ | Leaf _ -> acc
+ | Var i -> if (List.mem i acc) then acc else i::acc
+ | Node l -> List.fold_left aux acc l
+ in aux start_acc t
+;;