fib.erl

-module(fib).

-export([fib/1]).

%% api

%% @doc generates the fibonacci sequence - a naïve solution
-spec fib(N::pos_integer()) -> {pos_integer(), [pos_integer()]}.
fib(0) ->
  io:format("N must be greater than 0.\n");
fib(N) ->
  fib(0, N, []).

%% private

fib(C, N, Acc) when C == N ->
  {hd(Acc), lists:reverse(Acc)};
fib(C, N, Acc) ->
  fib(C+1, N, f(C+1, Acc)).

%% helpers

f(0, _Acc) -> [];
f(1, Acc) -> [0] ++ Acc;
f(2, Acc) -> [1] ++ Acc;
f(N, Acc) -> [lists:nth(1, Acc) + lists:nth(2, Acc)] ++ Acc.