Float to numerator and denominator

teammatt3 posted this at 03:35 — 9th January 2009.

Joined: Sep 2003

I'm trying to break up a float into a numerator and denominator.

For example, 1.65 would be 165/100, .5 would be 5/10. This is what I'm using:

<?php
// get the whole part
$whole = (int)$fraction_str;
        
// find the decimal point, and get everything after it
$decimal_position = strpos($fraction_str, '.');
$decimal = substr($fraction_str, $decimal_position + 1);

$numerator = (int)($whole . $decimal);
$denominator = pow(10, strlen($decimal));

// watch for negative on floats with no whole part
if($whole == 0 && (float)$fraction_str < 0)
    $numerator *= -1;
?>

It works (so far) but is there a better way? When I start using more math operators (as opposed to string functions), I run into the classic precision problems. (Like when 1.65 turns into 1.6499999)

pr0gr4mm3r posted this at 04:35 — 9th January 2009.

He has: 1,502 posts

Joined: Sep 2006

That looks like the easiest way. Your method is the simplest of the other ones I've found. You might want to typecast it to a float first to make sure you aren't fed the right number format.