Is this a thing? I', in the process of upgrading from ACF2016 to 2021 and during testing I found this.. I have 3 mysql DB fields, total, tax, shiptotal. All defined as DECIMAL(12,2) When I query the row, and then, in CF, add them together

grandTotal=val(h.total)+val(h.tax)+val(h.shiptotal);

when serializing the total to send back in Ajax I get "847.8100000000001" but when I output it to page or cfdump the result I get 847.81, as expected.. edited to add, in ACF2016

You need to use precisionEvaluate(). You've run afoul of floating point math.

lol, yeah, but when you add 2 decimal places to 2 decimal places... where in the heck do the floaty bits even come from? I get it for * & /, but + and -? and why only during serialization? When did precisionEvaluate() get added, thanks for that pointer btw

Because decimal values that look simple for us don't have a simple way to represent them internally as binary

i heard some great advice recently. work in cents. if we know its always 2 decimal places, multiply by 100 and do everything in whole numbers

damn, I hate it when someone pulls the binary sorcery card.

That's a good idea Scott - from today forward..sigh

same

at least in this case

replace(decimalformat(number,',','','all')

will solve it, I don't even want to think how many pennies I have lost (or gained) have happened before now.. reminds me of Richard Pryor's bank hack

Here are some other forum posts that also discuss floating point math https://dev.lucee.org/t/strange-result-floating-point-maths/11267/8 https://stackoverflow.com/questions/322749/retain-precision-with-double-in-java

Sad thing is, right after you said binary, I got it, but in all my years of doing this it never occurred to me that adding and subtracting the same decimal places would cause it to rear its ugly head. * & / I have always kept an eye out for it. New trick for an old dog.. I'll be formatting all decimals from all calculations from now on; thankfully I don't work on anything that will change the world as we know it..

Yeah, I get it. It's one of those things that smacks you up side the face one day and you can't believe the bedrock of basic math operations has the ability to go sideways so easily.

I switched from dbtype float to decimal for something similar I noticed years ago with *&/, I kinda feel stoopid that I didn't even consider +&-

Here's a fun trick to visualize the binary representation of a given decimal. I ran this from the CommandBox REPL. The first one is

.1

and the second one is

.5

CFSCRIPT-REPL: createObject( 'java', 'java.lang.Long' ).toBinaryString( createObject( 'java', 'java.lang.Double' ).doubleToLongBits( .1 ) )
11111110111001100110011001100110011001100110011001100110011010

CFSCRIPT-REPL: createObject( 'java', 'java.lang.Long' ).toBinaryString( createObject( 'java', 'java.lang.Double' ).doubleToLongBits( .5 ) )
11111111100000000000000000000000000000000000000000000000000000

now you are just getting a little too "weedy" for me, I'll keep to the trees

puff puff pass..