rotate list around list of Nth elements

rotate.erl

-module(rotate).
-export([rotate/2]).

rotate(N, List) -> 
  if
    is_number(N) ->
      rot([N], List);
    true -> rot(N, List)
  end.

rot([], List)  -> List;
rot([0|Ns], List) -> rot(Ns, List);
rot([1|Ns], List) -> rot(Ns, List);
rot([N|Ns], List) ->
  if
    N > length(List) -> rot(Ns, List);
    N < 0 -> rot(Ns, List);
    N >= 0 ->
      {List1, List2} = lists:split(N-1, List),
      rot(Ns, List2 ++ List1)
  end.