These are the pitfalls of a dynamically typed language, and FLOAT/INT conversions.
Your number1 is a string, number2 is a Double, and your number 3 is a string: <cfoutput> number3 is #number3.getClass().getName()#<br /> number2 is #number2.getClass().getName()#<br /> number1 is #number1.getClass().getName()#<br /> </cfoutput> If you do val() they will equal out: <cfif val(number3) eq val(number2)>Number3 equals number2<BR> <cfelse>Number3 does NOT equal number2<BR></cfif> From http://docs.sun.com/source/806-3568/ncg_goldberg.html#680, "the result of a floating-point calculation must often be rounded in order to fit back into its finite representation. This rounding error is the characteristic feature of floating-point computation." Checkout this code: <cfoutput> #(0.1 * 0.1) EQ 0.01# <!--- not equal! ---> #0.1 * 0.1# <!--- 0.1 multiplied by 0.1 is actually 0.01, so why aren't they equal? ---> #javacast("bigDecimal", 0.1 * 0.1)# <!--- results in 0.010000000000000002 ---> </cfoutput> If you need strict computation, stick to Doubles or bigDecimals all the time, and don't rely on implicit conversions. Also this is not a CF thing or a Java thing, other languages plague this too i.e Python (for division, 3/4 is different from 3.0/4.0) and .NET (http://stefanoricciardi.com/2010/03/02/comparing-floating-point-numbers/), and PHP (http://it.slashdot.org/story/11/01/06/1820208/PHP-Floating-Point-Bug-Crashes-Servers <http://it.slashdot.org/story/11/01/06/1820208/PHP-Floating-Point-Bug-Crashes-Servers?from=rss> or just start typing in google instant, php floating... and you'll see all the suggestions hehe) On 2/3/2011 12:56 PM, Jen McVicker wrote: > number1 (evaluate(12.5 * 1.1)): 13.75 > number2 (12.5 * 1.1): 13.75 > number3 (13.75): 13.75 > 13.75 - 13.75: 0 > 13.75 - 13.75: -1.7763568394E-015 > Number3 equals number1 > Number3 does NOT equal number2 > > > > Obviously number2 is set to a reference of the expression rather than the > actual value that is returned. But since the variable outputs as 13.75, why > does it make a difference? Can someone explain it to me in small words so > that I will understand? ;-) > > > > Jen Perkins McVicker > Adobe Certified ColdFusion Developer > Email: [email protected] > > Linked In: http://www.linkedin.com/in/jmcvicker > > > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Order the Adobe Coldfusion Anthology now! http://www.amazon.com/Adobe-Coldfusion-Anthology/dp/1430272155/?tag=houseoffusion Archive: http://www.houseoffusion.com/groups/cf-talk/message.cfm/messageid:341853 Subscription: http://www.houseoffusion.com/groups/cf-talk/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/groups/cf-talk/unsubscribe.cfm
