Rat to Str

rat2str.pl

use v6;

sub rat2str(Rat $rat is copy, :$base = 10) {
	my @str;
	if $rat < 0 {
		@str.push('-');
		$rat = -$rat;
	}

	my ($num, $denom) = $rat.nude;
	@str.push: ($num div $denom).base($base), '.';
	$num mod= $denom;

	if $num == 0 {
		@str.push('0');
		return @str.join;
	}

	my %seen;
	loop {
		%seen{$num} = +@str;
		$num *= $base;
		while $num < $denom {
			$num *= $base;
			@str.push('0');
		}

		@str.push: ($num div $denom).base($base);
		$num mod= $denom;
		last if $num == 0;

		if %seen.exists($num) {
			@str.splice(%seen{$num}, 0, '(');
			@str.push(')');
			last;
		}
	}

	return @str.join;
}

say .nude.join('/') ~ ' = ' ~ rat2str $_
	for 42.0, 1/5, -4/3, 19/12, 1/97;