(motive : Option Std.Tactic.BVDecide.LRAT.IntAction → Sort u_1) →
  (step? : Option Std.Tactic.BVDecide.LRAT.IntAction) →
    ((step : Std.Tactic.BVDecide.LRAT.IntAction) → motive (some step)) → (Unit → motive none) → motive step?