Luhn checksum check with Erlang

luhn.erl

-module(luhn).

-export([check/1]).


-spec check([integer()]) -> boolean().
check(Number) ->
    {Check, _} = lists:foldr(
        fun
            (N, {A, odd}) ->
                {A + N, even};
            (N, {A, even}) ->
                N1 = case N * 2 of
                    Big when Big > 9 -> Big - 9;
                    Small -> Small
                end,
                {A + N1, odd}
        end, {0, odd}, Number),
    (Check rem 10) == 0.