euler27

euler27.erl

-module(euler27).

%% API exports
-export([run/0]).

%%====================================================================
%% API functions
%%====================================================================

run() -> lists:foldl(
	  fun({A, B}, {Longest, Product}) -> 
			  QuadFn = quad(A,B),
			  RunLength = countConsecutivePrimes(QuadFn),
			  if RunLength > Longest -> {RunLength, A*B};
			     RunLength =< Longest -> {Longest,  Product}
			  end
	  end,
	  {0, 0},
	  values()
	  ) .

%%====================================================================
%% Internal functions
%%====================================================================
%%
 
values() -> [ {X, Y} || X <-lists:seq(-1000,1000), Y <- lists:seq(-1000,1000)]. 

quad(A,B) -> fun(N) -> N * N + A * N + B end .

countConsecutivePrimes(Fn) -> count_acc(Fn, 0) .

count_acc(QuadFn, N) -> 
	case primes:is_prime(QuadFn(N)) of
	   true -> count_acc(QuadFn, N+1);
	   false -> N
	end.