anchor.diff:  
   decr_counter(CounterPid) ->
       CounterPid ! down.
  +
  +count_test() ->
  +    ?assert(eqc:quickcheck(prop_count_correct())).
  +
  +prop_count_correct() ->
  +    ?FORALL(List, list(bool()),
  +            count(fun(E) -> E end, List) =:= length([E || E <- List, E])).
   
   multi_keydelete_test_() ->
       Languages = [{lisp, 1958},
  
positive.code:          safe_rpc/5,
           rpc_every_member/4,
           rpc_every_member_ann/4,
           keydelete/2,
           multi_keydelete/2,
           multi_keydelete/3,
  
negative.code: 	{error, {already_started, App}} ->
  	    ok
      end.
  
  %% @doc Applies `Pred' to each element in `List', and returns a count of how many
  %% applications returned `true'.
  -spec count(fun((term()) -> boolean()), [term()]) -> non_neg_integer().
  count(Pred, List) ->
      FoldFun = fun(E, A) ->
                        case Pred(E) of
                            false -> A;
                            true -> A + 1
                        end
                end,
      lists:foldl(FoldFun, 0, List).
  
  %% @doc Returns a copy of `TupleList' where the first occurrence of a tuple whose
  %% first element compares equal to `Key' is deleted, if there is such a tuple.
  