let pp_node_type fmt n = match n with
| Vstart -> Format.fprintf fmt "<start>"
| VfctIn -> Format.fprintf fmt "<fctIn>"
| VfctOut -> Format.fprintf fmt "<fctOut>"
| Vend -> Format.fprintf fmt "<end>"
| Vexit -> Format.fprintf fmt "<exit>"
| VblkIn (bk,_) -> Format.fprintf fmt "<blkIn-%d>" (bkind_sid bk)
| VblkOut (bk,_) -> Format.fprintf fmt "<blkOut-%d>" (bkind_sid bk)
| VcallIn (s, _, _, _) -> Format.fprintf fmt "<callIn-%d>" s.sid
| VcallOut (s, _, _, _) -> Format.fprintf fmt "<callOut-%d>" s.sid
| VcallExit (s, _, _, _) -> Format.fprintf fmt "<callExit-%d>" s.sid
| Vstmt s -> Format.fprintf fmt "<stmt-%d>" s.sid
| Vtest (b, s, _) ->
Format.fprintf fmt "<test%s-%d>" (if b then "In" else "Out") s.sid
| Vswitch (s,_) -> Format.fprintf fmt "<switch-%d>" s.sid
| Vloop (_, s) -> Format.fprintf fmt "<loop-%d>" s.sid