Project Euler. Problem 8.

euler8.erl

-module(euler8).
-export([start/0]).

start() ->
  lists:max(start_acc("7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450", [])).

start_acc(List, Acc) when length(List) >= 5 ->
  {Head, _} = lists:split(5, List),
  [_ | Tail] = List,
  start_acc(Tail, Acc ++ [product(Head)]);

start_acc(_, Acc) ->
  Acc.

product(List) ->
  product_acc(List, 1).

product_acc([], Acc) ->
  Acc;

product_acc(List, Acc) ->
  {Head, Tail} = lists:split(1, List),
  product_acc(Tail, erlang:list_to_integer(Head)*Acc).