four_arg_fib.erl

-module(four_arg_fib).
-export([fib/1, test_fib/0]).

%four argument fib function
fib(N) ->
    fib(0, 0, 1, N).
fib(From, Current, _Next, From) ->
    Current;
fib(From, Current, Next, To) ->
    fib(From+1, Next, Current + Next, To).


%test four argument fib function
test_fib() ->
    (fib(0) == 0) andalso (fib(1) == 1) andalso (fib(4) == 3).

This looks good :)