anchor.diff:      | MisMatch(i, j) -> MisMatch(i, j)
       | _ -> HeadMatch
   
  +// GM: This is unused, maybe delete
   let and_match m1 m2 =
       match m1 with
       | MisMatch (i, j) -> MisMatch (i, j)
  
positive.code: 
      | _ -> MisMatch(delta_depth_of_term env t1, delta_depth_of_term env t2)
  
  (* Does t1 match t2, after some delta steps? *)
  let head_matches_delta env wl t1 t2 : (match_result * option<(typ*typ)>) =
      let maybe_inline t =
          let head, _ = U.head_and_args t in
  
negative.code:             | _ -> success n_delta r t1 t2 in
      let r = aux true 0 t1 t2 in
      if Env.debug env <| Options.Other "RelDelta" then
          BU.print4 "head_matches_delta (%s, %s) = %s (%s)\n"
              (Print.term_to_string t1)
              (Print.term_to_string t2)
              (string_of_match_result (fst r))
  