Tail recursive erlang

trecursive.erl

-module(trecursive).

-export([fib/1,perfect/1,test/0]).

fib(X) -> fib(X,0,1).


fib(0,Acc1,_) -> 
	Acc1;
fib(X,Acc1,Acc2) when X >= 1 -> 
	fib(X-1,Acc2,Acc1 + Acc2). 

%Steep by steep:
%fib(4) -> fib(4,0,1).
%fib(4,0,1) -> fib(3,1,0 + 1).
%fib(3,1,1) -> fib(2,1,1 + 1).
%fib(2,1,2) -> fib(1,2,1 + 2).
%fib(1,2,3) -> fib(0,3,3 + 2).
%fib(0,3,5) -> 3.


perfect(X) -> perfect(X,1,0).
%Moddifeid according to brujoBenavides review:
%perfect(X,Divisor,Acc) when X == Divisor andalso X == Acc ->
perfect(X,X,X) -> 
	true;
%perfect(X,Divisor,_) when X == Divisor -> 
perfect(X,X,_) -> 
	false;
perfect(X,Divisor,Acc) when X rem Divisor == 0 ->
	perfect(X,Divisor +1 ,Acc + Divisor);
perfect(X,Divisor,Acc) ->
	perfect(X,Divisor +1 ,Acc).


test() ->
	3 = fib(4),
	true = perfect(6),
	true = perfect(28),
	false = perfect(10),
	success.

Good job! One tip: You can use pattern-matching more aggressively…

perfect(X,X,X) -> 
	true;
perfect(X,X,_) -> 
	false;
…

Yeah, thank you! I missed that.