Re: Math weirdness with doubles...

They are not the same amount. They each got a different rounding error. Double values only display a small number of decimal places (relatively speaking). If you look at the difference you're getting, it's 0.0000000000000142108547152 (I may be off by a zero or two), so given you're working with a currency, I'd say you can safely round to about 4 or 8 decimal places to get a reasonably accurate result. I typically use 4 since most money types I've seen only go out 4 decimal places to begin with. -- D. Wokan (Sorry for the double reply, Jon. Didn't realise this list doesn't set the reply-to until it was too late.) jon roig wrote: > Ok... It's Friday and maybe my brain is dead, but I'm having a weird > problem with some basic math. > > Here's a little snippet of the code I'm working with: > > --------------------------- > echo "<p>Current:$currentAmount:".gettype($currentAmount)." - > Paid:$paidAmount:".gettype($paidAmount)."</p>"; > > $currentAmount = $currentAmount-$paidAmount; > echo "<p>Final Current: $currentAmount"; > ----------------- > > Straightforward... Yeah? > > Here's a sample of the output: > Current:97.6:double - Paid:97.6:double > Final Current: 1.42108547152E-014 > > Now if both $currentAmount and $paidAmount are doubles, subtracting them > should yield a zero, shouldn't it? > > -- jon > > ------------------- > jon roig > web developer > email: jon@trafficdesigns.com > phone: 888.230.7557 > > --- > Outgoing mail is certified Virus Free. > Checked by AVG anti-virus system (http://www.grisoft.com). > Version: 6.0.593 / Virus Database: 376 - Release Date: 2/20/2004 > >