Course of Raku / Essentials / Creating and calling functions

Returning the result

Functions often not just do something but also return a result. For example, in functional programming, functions should not produce any side effects such as printing to console. Nevertheless, Raku does not limit you from doing so. Let’s see how to return a value from a function and how to get it in the calling code.

sub add($x, $y) {
    return $x + $y;
}

my $sum = add(10, 20);
say $sum; # 30

Here, the function called add takes two numbers and returns their sum. An explicit return is used. On the calling side, the value the function returns can be used as any other value. In the above program, it is assigned to a variable.

The last evaluated value

In Raku, an explicit return is not required if the result that you want to return from a function is the last computed value in its body. Our add function can be simplified:

sub add($x, $y) {
    $x + $y
}

As you may have noticed, there is no semicolon at the end of the line as it is not required when the line ends the current code block.

Such trivial and small functions are often formatted in a single line for a more compact code:

sub add($x, $y) { $x + $y }

No return data

If you need to return from a function before the end of its body, and the function does not return any result, use a bare return.

sub test($x) {
    return if $x <= 10;
    say "$x is above the limit";
}

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