Convert decimal number to rational

Decimals are natively represented as rationals in Raku, so if the task does not need to handle repeating decimals, it is trivially handled by the .nude method, which returns the numerator and denominator:

say .nude.join('/') for 0.9054054, 0.518518, 0.75;

Output:

4527027/5000000
259259/500000
3/4

However, if we want to take repeating decimals into account, then we can get a bit fancier.

sub decimal_to_fraction ( Str $n, Int $rep_digits = 0 ) returns Str {
    my ( $int, $dec ) = ( $n ~~ /^ (\d+) \. (\d+) $/ )».Str or die;

    my ( $numer, $denom ) = ( $dec, 10 ** $dec.chars );
    if $rep_digits {
        my $to_move = $dec.chars - $rep_digits;
        $numer -= $dec.substr(0, $to_move);
        $denom -= 10 ** $to_move;
    }

    my $rat = Rat.new( $numer.Int, $denom.Int ).nude.join('/');
    return $int > 0 ?? "$int $rat" !! $rat;
}

my @a = ['0.9054', 3], ['0.518', 3], ['0.75', 0], | (^4).map({['12.34567', $_]});
for @a -> [ $n, $d ] {
    say "$n with $d repeating digits = ", decimal_to_fraction( $n, $d );
}

Output:

0.9054 with 3 repeating digits = 67/74
0.518 with 3 repeating digits = 14/27
0.75 with 0 repeating digits = 3/4
12.34567 with 0 repeating digits = 12 34567/100000
12.34567 with 1 repeating digits = 12 31111/90000
12.34567 with 2 repeating digits = 12 17111/49500
12.34567 with 3 repeating digits = 12 1279/3700