Course of Raku / Essentials / Creating and calling functions / Exercises / Recursive factorial

Solution: Recursive factorial

Factorial is a very productive exercise, as it can be solved in a number of different ways. This time we are using recursion, which means that the function is called from itself.

Code 1

Here is the code of the solution. Notice that you need to check the condition to stop the recursion, otherwise it will continue infinitely.

sub factorial($n) {
    if $n < 2 {
        return 1;
    }
    else {
        return $n * factorial($n - 1);
    }
}

say factorial(10);

🦋 Find the program in the file recursive-factorial.raku.

Code 2

In the cases, as shown in this code, it is often better to use postfix forms of if to immediately return from the function. This approach clears the code and removes a lot of indentation and punctuation.

sub factorial($n) {
    return 1 if $n < 2;
    return $n * factorial($n - 1);
}

say factorial(10);

🦋 Find the updated program in the file recursive-factorial-2.raku.

Example

Run the program and check the result. By the way, did you know that 10! is the exact number of seconds in six weeks?

$ raku exercises/functions/recursive-factorial.raku
3628800

Course navigation

← Associative data types / Interpolating hashes   |   More about functions →