tailrecursion.erl

-module(tailrecursion).
-export([loop/1, fib/1, perfect/1, test_perfect_number/0, test_fib/0]).


loop(N) when N > 0 ->
    io:format("~p~n", [N]),
    loop(N-1);
loop(_N) ->
    io:format("bye ~n").

fib(N) ->
    fib(N, 0, 1).
fib(0, Result, _Next) -> 
    Result;
fib(N, Result, Next) when N > 0 ->
    fib(N-1, Next, Result + Next).

% fib(4) 
%     = fib(4, 0, 1)
%     = fib(3, 1, 1)
%     = fib(2, 1, 2)
%     = fib(1, 2, 3)
%     = fib(0, 3, 5)
%     = 3.
% 0, 1, 1, 2, 3

perfect(0) ->
    false;
perfect(N) when N > 0 ->
    perfect(N div 2, N, 0).

perfect(0, Number, Number) ->
    true;
perfect(0, _, _) ->
    false;
perfect(Divisor, Number, Accumulator) ->
    if 
        Number rem Divisor == 0 ->
            NewAccumulator = Accumulator + Divisor;
        true ->
            NewAccumulator = Accumulator
    end,
    perfect(Divisor-1, Number, NewAccumulator).



test_perfect_number() ->
    (perfect(5) == false) andalso (perfect(6) == true) andalso (perfect(0) == false).

test_fib() ->
    (fib(0) == 0) andalso (fib(1) == 1) andalso (fib(4) == 3).

I am not sure we covered case syntax in the videos.
I had asked earlier should we read a text along with the videos ?

Well… we certainly didn't cover if syntax either. If you want do work with just what's on the videos you need to use another function…

NewAccumulator = update_accumulator(Number rem Divisor, Divisor, Accumulator),

…

update_accumulator(0, Divisor, Accumulator) -> Accumulator + Divisor;
update_accumulator(_, _, Accumulator) -> Accumulator.

There are several books and resources to reed attached to the first or second video of Week 1.

will start reading.

elbrujohalcon please check https://gist.github.com/pppillai/63bce02dc627227de7181e0e68e27ccd