Lazy list generator in erlang.

llist.erl

-module (llist).

-compile(export_all).

unfold(X, F) ->
  case F(X) of
    {ok, X1} -> [X1 | fun() -> unfold(X1, F) end];

    false    -> []
  end.

generator(Project, Last) ->
  fun (X) ->
    case Last(X) of
      true  -> false;

      false -> {ok, Project(X)}
    end
  end.

head(LList) -> hd(LList).
tail(LList) -> (tl(LList))().

force([]) -> [];
force([Val | Next]) -> [Val | force(Next())].