anchor.diff:      {wl with ctr=wl.ctr + 1}
   
   let extend_solution pid sol wl =
  -    if Env.debug wl.tcenv <| Options.Other "RelCheck"
  +    if Env.debug wl.tcenv <| Options.Other "Rel"
       then BU.print2 "Solving %s: with [%s]\n" (string_of_int pid) (List.map (uvi_to_string wl.tcenv) sol |> String.concat ", ");
       commit sol;
       {wl with ctr=wl.ctr+1}
  
positive.code:             TProb p, wl
          in
          let pairwise t1 t2 wl =
              if Env.debug env <| Options.Other "RelCheck"
              then BU.print2 "pairwise: %s and %s" (Print.term_to_string t1) (Print.term_to_string t2);
              let mr, ts = head_matches_delta env () t1 t2 in
              match mr with
  
negative.code:          let head1 = U.head_and_args t1 |> fst in
           let head2 = U.head_and_args t2 |> fst in
           let _ =
               if debug env (Options.Other "Rel")
               then BU.print3 ">> (%s)\n>>> head1 = %s\n>>> head2 = %s\n" (string_of_int problem.pid)
                                   (Print.term_to_string head1)
                                   (Print.term_to_string head2)
  