method category = function
| Never_tried | Unknown _ -> st_unknown <- succ st_unknown ; "-"
| Considered_valid -> st_extern <- succ st_extern ; "Extern"
| Valid _ -> st_complete <- succ st_complete ; "Valid"
| Invalid _ -> st_bug <- succ st_bug ; "Bug"
| Valid_under_hyp _ -> st_partial <- succ st_partial ; "Partial"
| Invalid_under_hyp _ -> st_alarm <- succ st_alarm ; "Alarm"
| Valid_but_dead _ | Invalid_but_dead _ | Unknown_but_dead _ ->
st_dead <- succ st_dead ; "Dead"
| Inconsistent _ -> st_inconsistent <- succ st_inconsistent ; "Unsound"