anchor.diff:  %%%   redundant I/Os.
   %%% - Our use cases only want sets, so this does not associate
   %%%   attributes with the keys.
  +%%% - Bulk-loading into an empty tree has been added.
   %%%
   %%%----------------------------------------------------------------
   %%%
  
positive.code:            pageid = ?NOPAGEID,
             p0 = ?NOPAGEID,
             e = {}}}.
  
  %%%_* Membership check =========================================================
  %%%
  
negative.code: 
  -module(btree).
  -export([ new/1
          , from_list/3
          , member/3
          , all_keys/2
          , insert/3
  