Re: help with float numbers

pdmytrew@lexmark.com wrote: > I have quite a frustrating problem that I *think* involves floating-point > ('double') numbers. I have the following code: Yes. Internally they are represented by "chopped off" decimals with, like, lots of digits, but not infinite. So 1/3 will never be exactly 1/3. Perhaps suprisingly, 1/2 will most likely never be 1/2 either, because the internal representation is, well, it's a bit complicated to go into, but just assume that ALL fractions are infinitely repeating when they turn into decimals and they get rounded off a bit. > $Total = array_sum($Activity); > if ($Total == 100) { > > // do some stuff > > } else { > $Message = "Total is $Total! Please check your numbers.\n"; > } > > If $Activity has values like (25 , 25 , 25 , 25), then it works just fine. > But if $Activity is an array of the following: (71.8 , 5.6 , 5.6 , 8.5 , 8.5) > I get the message "Total is 100! Please check your numbers." > I don't understand!!! > If Total is 100, then why doesn't that meet the condition of the first if-statement ?! > I suspect it has something to do with the way PHP deals with integers vs. floating-point > numbers. Yes? > For my purposes, $Activity may have all integers, all decimals, or a combination of both like > (25, 25, 25, 12.5, 12.5). > I'm using PHP 4.3.1. What can I do to allow for this? How do I compare an integer (100) to > what MAY OR MAY NOT be a float ($Total)? Are you simply checking that the total percentages add up to 100? Perhaps it would be sufficient to say: $Total = round(array_sum($Activity)); Or, perhaps you could even get away with: if ($Total > 99 and $Total < 101){ Or... It *REALLY* depends on your application and *WHY* you need this, rather than having some cut-and-dried answer. You may even need to be 100% (pun intended) accurate and dive into BC MATH http://php.net/bc Or not. Just depends what you are trying to do.