<# File: 004_factorial.falak
   Computes factorials using iteration and recursion.
   (C) 2021 Ariel Ortiz, ITESM CEM.
#>

# Iterative version for computing factorial of n.
iterative_factorial(n) {
    var result, i;
    result = 1;
    i = 2;
    while (i <= n) {
        result = result * i;
        inc i;
    }
    return result;
}

# Recursive version for computing factorial of n.
recursive_factorial(n) {
    if (n <= 0) {
        return 1;
    } else {
        return n * recursive_factorial(n - 1);
    }
}

main() {
    var num, option;
    do {
        prints("Input a number: ");
        num = readi();
        prints("Iterative factorial: ");
        printi(iterative_factorial(num));
        println();
        prints("Recursive factorial: ");
        printi(recursive_factorial(num));
        println();
        prints("Compute another factorial? ");
        option = reads();
        if (size(option) == 0) {
            option = 'N';
        } else {
            option = get(option, 0);
        }
    } while (option == 'Y' || option == 'y');
}