Implement in Erlang the lazy evaluation/streaming approach taught by Nathan Dotz at CodeMash 2017.

thunk.erl

-module(thunk).
-compile(export_all).

%% > thunk:take(3, thunk:forever_zero()).
%% [0,0,0]
%% > thunk:take(3, thunk:fib()).
%% [1,1,2]
%% > thunk:take(18, thunk:fib()).
%% [1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,1597,2584]

take(0, _Stream) ->
    [];
take(N, Stream) ->
    [hd(Stream())|take(N-1, (tl(Stream())))].

forever_zero() ->
    fun() -> [0 | forever_zero()] end.

fib() ->
    F = fun Fib(A, B) ->
                fun() ->
                        [A | Fib(B, A+B)]
                end
        end,
    F(1, 1).