How much precision for a bcmath PHP library? <p>I'm writing a PHP library that has a Number class that uses the <a href="http://us2.php.net/manual/en/book.bc.php" rel="nofollow noreferrer"><code>bcmath</code> extension</a> for arbitrary precision.</p> <p>I have two questions:</p> <ol> <li><p>How much slower is bcmath compared to using the built-in int and float types?</p></li> <li><p><code>bcmath</code> has an optional <a href="http://us2.php.net/manual/en/function.bcscale.php" rel="nofollow noreferrer">scale argument</a> (that defaults to 3 digits). For an general purpose Number class that anyone could use, what would be a good level of precision? How do languages like Perl (that have arbitrary precision numbers) deal with scale?</p></li> </ol>