anchor.diff:  decode([0|Rest], {L={_,_}, _}, Tree, Result) ->
   	decode(Rest, L, Tree, Result);
   
  -decode(L, {Sym,-1},  Tree, Result) -> 
  +decode(L, {Sym, -1},  Tree, Result) -> 
   	decode(L, Tree, Tree, [Sym|Result]).
   
  -descomprimir(Entrada, Salida) -> 
  -	{ok, Binary} = file:read_file(Entrada),
  -	{Tree, Code} = read_tree(Binary),
  -	Dump = decode(Code, Tree),
  -	ok = file:write_file(Salida, Dump).
  
positive.code: main([Opt,Entrada,Salida]) when Opt =:= 'd' -> descomprimir(Entrada, Salida);
  main([_]) -> io:format(?USAGE).
  
  
  
  comprimir(Entrada, Salida) -> 
  	{ok, Binary} = file:read_file(Entrada),
  	Bytes = binary_to_list(Binary),
  
negative.code: 	{Block, Rest} = lists:splitwith(fun (X) -> X == Head end, Tail),
  	calc_freqs(Rest, [{Head, 1+length(Block)} | Acum]).
  
  % decode a binary using Tree
  decode(Code, Tree) -> 
  	L = [X || <<X:1>> <= Code],
  	decode(L, Tree, Tree, []).
  