anchor.diff:  (* This is used when computing WHNFs                               *)
   (*******************************************************************)
   let rec closure_as_term cfg (env:env) t =
  -    log cfg  (fun () -> BU.print2 ">>> %s Closure_as_term %s\n" (Print.tag_of_term t) (Print.term_to_string t));
  +    log cfg (fun () -> BU.print2 ">>> %s Closure_as_term %s\n" (Print.tag_of_term t) (Print.term_to_string t));
       match env with
           | [] when not <| cfg.steps.compress_uvars -> t
           | _ ->
  
positive.code: 
  let maybe_simplify cfg env stack tm =
      let tm' = maybe_simplify_aux cfg env stack tm in
      if Env.debug cfg.tcenv <| Options.Other "380"
      then BU.print3 "%sSimplified\n\t%s to\n\t%s\n"
                     (if cfg.steps.simplify then "" else "NOT ")
                     (Print.term_to_string tm) (Print.term_to_string tm');
  
negative.code:     List.map stack_elt_to_string s |> String.concat "; "
  
  let log cfg f =
      if cfg.debug.gen then f () else ()
  
  let log_primops cfg f =
      if cfg.debug.primop then f () else ()
  
  let is_empty = function
      | [] -> true
  