fix: Add arrow back in dot visu for directed graphs

tools/rdbg4sasa/dot4sasa.ml

@@ -160,9 +160,11 @@ let to_pdf engine par_var only_parent rn g f e =
          (fun n ->
             let l = g.succ n.id in
             List.mapi (fun i t ->
-                if is_parent "par" n.id i e then
+                if g.directed then            
+                  Printf.sprintf "%s -> %s" t n.id  
+                else if is_parent "par" n.id i e  then
                   Printf.sprintf "%s -> %s" n.id t 
-                else if n.id < t then
+                else if n.id < t then (* to avoid duplication in undir graphs *)
                   Printf.sprintf "%s -- %s" n.id t
                 else
                   Printf.sprintf "%s -- %s" t n.id