let subproof_idx id = match id.p_kind with
| PKProp | PKPre _ | PKPropLoop -> 0 (* 1/1 *)
| PKPreserved -> 0 (* 1/2 *)
| PKEstablished-> 1 (* 2/2 *)
| PKVarDecr -> 0 (* 1/2 *)
| PKVarPos -> 1 (* 2/2 *)
| PKAFctOut -> 0 (* 1/2 *)
| PKAFctExit -> 1