+let remove node = List.filter (fun node' -> node <=> node');;
+
+let add_leq_arc ((_,_,leq,_) as node) ((_,_,_,geq') as node') =
+ leq := node' :: !leq;
+ geq' := node :: !geq'
+;;
+
+let add_geq_arc ((_,_,_,geq) as node) ((_,_,leq',_) as node') =
+ geq := node' :: !geq;
+ leq' := node :: !leq'
+;;
+
+let remove_leq_arc ((_,_,leq,_) as node) ((_,_,_,geq') as node') =
+ leq := remove node' !leq;
+ geq' := remove node !geq'
+;;
+
+let remove_geq_arc ((_,_,_,geq) as node) ((_,_,leq',_) as node') =
+ geq := remove node' !geq;
+ leq' := remove node !leq'
+;;
+
+let leq_transitive_closure node node' =
+ add_leq_arc node node';
+ let rec remove_transitive_arcs ((_,_,_,geq) as node) (_,_,leq',_) =
+ let rec remove_arcs_to_ascendents =
+ function
+ [] -> ()
+ | (_,_,leq,_) as node'::tl ->
+ remove_leq_arc node node';
+ remove_arcs_to_ascendents (!leq@tl)
+ in
+ remove_arcs_to_ascendents !leq';
+ List.iter (function son -> remove_transitive_arcs son node) !geq
+ in
+ remove_transitive_arcs node node'
+;;
+
+let geq_transitive_closure node node' =
+ add_geq_arc node node';
+ let rec remove_transitive_arcs ((_,_,leq,_) as node) (_,_,_,geq') =
+ let rec remove_arcs_to_descendents =
+ function
+ [] -> ()
+ | (_,_,_,geq) as node'::tl ->
+ remove_geq_arc node node';
+ remove_arcs_to_descendents (!geq@tl)
+ in
+ remove_arcs_to_descendents !geq';
+ List.iter (function father -> remove_transitive_arcs father node) !leq
+ in
+ remove_transitive_arcs node node'
+;;
+
+let (@@) l1 n = if List.exists (function n' -> n===n') l1 then l1 else l1@[n]
+
+let rec leq_reachable node =
+ function
+ [] -> false
+ | node'::_ when node === node' -> true
+ | (_,_,leq,_)::tl -> leq_reachable node (!leq@tl)
+;;
+
+let rec geq_reachable node =
+ function
+ [] -> false
+ | node'::_ when node === node' -> true
+ | (_,_,_,geq)::tl -> geq_reachable node (!geq@tl)
+;;
+
+exception SameEquivalenceClass of set * equivalence_class * equivalence_class;;
+
+let locate_using_leq to_be_considered_and_now ((repr,_,leq,geq) as node)
+ set start
+=
+ let rec aux ((nodes,inf,sup) as set) already_visited =