Course of Raku / Addendum 🆕 / Working with data / Numbers and mathematics / Exercises / Perfect numbers

Solution: Perfect numbers

Here is a possible solution to the task.

Code

my @perfect = (1..30).grep: -> $n {
    $n == [+] (1..^$n).grep($n %% *)
};

say @perfect;

🦋 You can find the source code in the file perfect-numbers.raku.

Output

[6 28]

Comments

(1..^$n).grep($n %% *) keeps the numbers below $n that divide it evenly — its proper divisors. The %% * is a Whatever function that tests divisibility.
[+] sums those divisors, and the outer grep keeps only the numbers that are equal to that sum.

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