anchor.diff:      | Some state ->
           let digest = md5_of_file src_fn in
           if state.identity.source_digest = digest then
  -            fuel_trace := ReplayFuelTrace state.fuels
  +            fuel_trace := ReplayFuelTrace (val_fn, state.fuels)
           else
               fuel_trace := RecordFuelTrace []
       | None ->
  
positive.code: type fuel_trace_status =
      | FuelTraceUnavailable
      | RecordFuelTrace of list<(int * int)>
      | ReplayFuelTrace of list<(int * int)>
  
  let fuel_trace : ref<fuel_trace_status> = Util.mk_ref <| FuelTraceUnavailable
  
  
negative.code:         @[Term.CheckSat]
          @suffix in
  
      let check (p:decl) =        
          let cached_config =
              match !fuel_trace with 
              | ReplayFuelTrace (fname, hd::tl) ->
                  let fuel, ifuel = hd in
                  fuel_trace := ReplayFuelTrace (fname, tl);
                  Some (fname, fuel, ifuel)
              | _ ->
                  None
          in
          let initial_config = 
              match cached_config with 
              | Some (_, fuel, ifuel) -> (fuel, ifuel)
              | None -> (!Options.initial_fuel, !Options.initial_ifuel) 
          in
          let alt_configs = 
  