gistfile1.txt

sub r2s (Rat $rat, $base = 10) {
    my $s = $rat < 0 ?? '-' !! '';
    my $r = $rat.abs;
    my $i = $r.floor;
    $r -= $i;
    $s ~= $i.base($base);
    if $r {
	my $want = $r.denominator < $base**6 ?? 6 !! $r.denominator.log($base).ceiling + 1;
	my @f;
	while $r and @f < $want {
	    $r *= $base;
	    $i = $r.floor;
	    push @f, $i;
	    $r -= $i;
	}
	if $r >= 0.5 {
	    for @f-1 ... 0 -> $x {
		last if ++@f[$x] < $base;
		@f[$x] = 0;
		$s ~= ($i+1).base($base) if $x == 0; # never happens?
	    }
	}
	$s ~= '.';
	$s ~= [0..9,'A'..'Z'][@f].join;
    }
    $s;
}

say r2s(1/5000000000, 16);
say r2s(1/2000000000, 33);
say r2s(-(42+99999999999999/100000000000000), 2);
say r2s(:36<abigradixendswithz>/:36<10000000>, 36);