anchor.diff:      K :: term(),
       V :: term().
   
  -foldl(Fun, Init, Map) when is_function(Fun,3), is_map(Map) ->
  +fold(Fun, Init, Map) when is_function(Fun,3), is_map(Map) ->
       lists:foldl(fun({K,V},A) -> Fun(K,V,A) end,Init,maps:to_list(Map)).
  -
  --spec foldr(Fun,Init,Map) -> Acc when
  -    Fun :: fun((K,V,AccIn) -> AccOut),
  -    Init :: term(),
  -    Acc :: term(),
  -    AccIn :: term(),
  -    AccOut :: term(),
  -    Map :: map(),
  -    K :: term(),
  -    V :: term().
  -
  -foldr(Fun, Init, Map) when is_function(Fun,3), is_map(Map) ->
  -    lists:foldr(fun({K,V},A) -> Fun(K,V,A) end,Init,maps:to_list(Map)).
  -
   
   -spec map(Fun,Map1) -> Map2 when
       Fun :: fun((K, V1) -> V2),
  
positive.code: -module(maps).
  
  -export([
  	foldl/3,
  	foldr/3,
  	map/2,
  	size/1,
  	without/2
  
negative.code: 
  %%% End of BIFs
  
  -spec fold(Fun,Init,Map) -> Acc when
      Fun :: fun((K, V, AccIn) -> AccOut),
      Init :: term(),
      Acc :: term(),
  