anchor.diff:  
   % last prime in prime_cache/0
   -define(PrimeCache, 5003).
  -
  -%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  -
  --spec get_nearest_feeder(1..5250) -> {1..5250}.
  +-define(TESTER_MAX_PRIME, 5250).
  +
  +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  +
  +-spec get_nearest_feeder(1..?TESTER_MAX_PRIME) -> {1..?TESTER_MAX_PRIME}.
   get_nearest_feeder(N) -> {N}.
   
   % @doc returns first prime larger than N
  
positive.code: 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()}.
  find_primes_feeder(_Add, N, [] = Primes) ->
      {2, N, Primes};
  find_primes_feeder(Add, N, [H|_] = Primes) ->
  
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
  