anchor.diff:  get(N) ->
       find_primes(?PrimeCache, N, lists:reverse(prime_cache())).
   
  --spec find_primes_feeder(0 | 2, pos_integer(), rev_prime_list())
  -        -> {pos_integer(), pos_integer(), rev_prime_list()}.
  +-spec find_primes_feeder(0 | 2, 1..?TESTER_MAX_PRIME, rev_prime_list())
  +        -> {pos_integer(), 1..?TESTER_MAX_PRIME, rev_prime_list()}.
   find_primes_feeder(_Add, N, [] = Primes) ->
       {2, N, Primes};
   find_primes_feeder(Add, N, [H|_] = Primes) ->
  
positive.code: 
  % last prime in prime_cache/0
  -define(PrimeCache, 5003).
  
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  
  -spec get_nearest_feeder(1..5250) -> {1..5250}.
  get_nearest_feeder(N) -> {N}.
  
  % @doc returns first prime larger than N
  
negative.code: 
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  
  -spec get_feeder(1..?TESTER_MAX_PRIME) -> {1..?TESTER_MAX_PRIME}.
  get_feeder(N) -> {N}.
      
  % @doc returns all primes less than or equal to N
  