def zero(x) = 0;def suc(x) = x + 1;def pred(x) = if x == 0 then x else x - 1;def add(x, y) = if x == 0 then y else suc(add(x - 1, y));def mult(x, y) = if x == 0 then 0 else add(y, mult(x - 1, y));def pow(x, y) = if y == 0 then 1 else mult(x, pow(x, y - 1));def fib(n) = if n == 0 then 0 else if n == 1 then 1 else fib(n - 1) + fib(n - 2);def fact(n) = if n == 0 then 1 else n * fact(n - 1);def ack(m, n) = if m == 0 then n + 1 else if n == 0 then ack(m - 1, 1) else ack(m - 1, ack(m, n - 1));def stack_test(x) = x + 1 + 2 + 3 + 4 + 5;def div(x, y) = x / y; //integer divisiondef rem(x, y) = x % y; //remainderdef gcd(a, b) = if b == 0 then a else gcd(b, a % b);def is_prime_aux(n, i) = if n % i == 0 then 0 else if (i * i) <= n then is_prime_aux(n, i + 1) else 1;def is_prime(n) = if n == 2 then 1 else is_prime_aux(n, 2);def primes(n) = if n == 0 then 0 else if is_prime(n) == 1 then (write n; primes(n - 1)) else primes(n - 1);def is_collatz(n) = if n == 1 then 1 else if n % 2 == 0 then is_collatz(n / 2) else is_collatz(3 * n + 1); def collatz_aux(n, i) = if i > n then 0 else if is_collatz(i) == 1 then (write i; collatz_aux(n, i + 1)) else collatz_aux(n, i + 1);def collatz(n) = collatz_aux(n, 1);def facT(n, acc) = if n == 0 then acc else facT(n - 1, n * acc);//zero(3)//suc(8)//pred(7)//add(3, 4)//mult(4,5)//pow(2, 3)//fib(20)//(write(fact(5)) ; fact(6))//(write(1) ; 2)ack(3, 12) // for tail-rec test//stack_test(0)//(write (div(11, 3)); rem(11, 3))//gcd(54, 24)//is_prime(2)//primes(1000000)//collatz(5000)//facT(6, 1)