anchor.diff:    K = (L + R) div 2,
     KX = item_k(element(K, E)),
     if X < KX -> binsearch(E, X, L, K - 1);
  -     X =:= KX -> {found, K};
  +     X =:= KX -> ?found(K);
        true -> binsearch(E, X, K + 1, R)
     end;
   binsearch(_E, _X, _L, R) ->
  -  {not_found, R}.
  +  ?not_found(R).
   
   %%%_* B-tree Search ============================================================
   %%%
  
positive.code: %%%_* Binary search within a page ==============================================
  %%%
  %%% Search a page's item vector E for key X.
  %%% Return {found, K} if found at index K,
  %%% otherwise {not_found, R} where R is the index where the B-tree traversal
  %%% should descend.
  
  binsearch(E, X) ->
    binsearch(E, X, 1, size(E)).
  
negative.code: 
  search_page(IO, X, P = #page{p0 = P0, e = E}, Path) ->
    case binsearch(E, X) of
      ?not_found(R) ->
        Q =
          if R =:= 0 -> P0;
             true -> item_p(element(R, E))
          end,
        search_pageid(IO, X, Q, [{P, R} | Path]);
      ?found(K) ->
        {true, P, K, Path}
    end.
  
  