Course of Raku / Objects, I/O, and exceptions / Exceptions / Soft failures / Exercises / Soft reciprocal

Solution: Soft reciprocal

Here is a possible solution to the task.

Code

sub reciprocal($n) {
    fail 'no reciprocal of zero' if $n == 0;
    return 1 / $n;
}

say reciprocal(4);
say reciprocal(0) // 'undefined';

🦋 You can find the source code in the file soft-divide.raku.

Output

0.25
undefined

Comments

1. reciprocal(4) returns 1 / 4, that is 0.25, normally.

2. reciprocal(0) calls fail, so it returns a Failure, which is undefined. The // operator returns its right-hand side whenever the left side is undefined, so we get the fallback undefined.

3. Using // counts as handling the failure: it tests for definedness without using the value, so the Failure stays soft and is never thrown as a real exception.

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