tail_recursion.erl

-module(tail_recursion).
-export([fib/1,perfect/1]).
-export([fibTest/0,perfectTest/0]).

% Tail recursive fibonacci
fib(N) -> fib(N, 0, 1).
fib(0, A, _) -> A;
fib(N, A, B) -> fib(N-1, A+B, A).

fibTest() ->
  0 = fib(0),
  1 = fib(1),
  1 = fib(2),
  2 = fib(3),
  3 = fib(4),
  5 = fib(5),
  8 = fib(6),
  13 = fib(7),
  55 = fib(10),
  passed.

% Perfect numbers
perfect(1) -> false;
perfect(N) when N>1 -> perfect(N, N-1, 0).
perfect(N, 1, Ac) -> N == Ac + 1;
perfect(N, D, Ac) when N rem D == 0 -> perfect(N, D-1, Ac+D);
perfect(N, D, Ac) -> perfect(N, D-1, Ac).

perfectTest() ->
  false = perfect(1),
  false = perfect(2),
  true  = perfect(6),
  false = perfect(21),
  true  = perfect(28),
  false = perfect(42),
  true  = perfect(496),
  false = perfect(1024),
  true  = perfect(8128),
  passed.

Nicely done.

Remember that snake_case is preferred over camelCase, in general. Particularly for tests, frameworks like eunit will recognize functions called …_test/0 as tests and they'll not recognize functions like perfectTest/0. 🤷

Thanks! Is there any recommended code style checker/fixer for Erlang?

Yes! https://hex.pm/packages/rebar3_lint, which is based on https://github.com/inaka/elvis
And there are formatters, too… My favorite (and I'm not biased at all ) is https://hex.pm/packages/rebar3_format
(More about it on NextRoll's blog).

I will definitely look into it, thanks again! :)