How to move the decimal point N places to the left efficiently?
This is a bit verbose, but should do the trick:
sub move_point {
my ($n, $places) = @_;
die 'negative number of places' if $places < 0;
return $n if $places == 0;
my ($i, $f) = split /\./, $n; # split to integer/fractional parts
$places += length($f);
$n = sprintf "%0*s", $places+1, $i.$f; # left pad with enough zeroes
substr($n, -$places, 0, '.'); # insert the decimal point
return $n;
}
Demo:
my $n = "12.34";
for my $p (0..5) {
printf "%d %s\n", $p, move_point($n, $p);
}
0 12.34
1 1.234
2 0.1234
3 0.01234
4 0.001234
5 0.0001234