>>>A friend of mine asked this to me today. I said yes,0 with confidence and he said OK then go and put that in Excel as a formula.
>>>I thought it was an Excel bug but he turned and said it happens in SQL server with float datatype! I couldn't yet see that myself but trust his experience.
>>>Any idea and solution?
>>>TIA
>>
>>Cetin,
>>
>>How're doing? We haven't communicated in a long time.
>>
>>I just have a SWAG, but I think it might be right. I tested this will both Excel and VFP 9.0 and got completely different results. IOW, Excel returned false and VFP, correctly, returned true.
>>
>>The only thing that I can think of that might explain it is the Pentium class process floating point bug.
>>
>>In Excel, when I entered the equation, 1*(0.5-0.4-0.1), it returned -2.77556E-17. Naturally, this isn't equal to zero.
>>
>>Sorry, Cetin, that's all I've got. BTW, Congrats on being a "UT Personality".:-)
>
>Hi George,
>I'm fine and busy all day:)
>I initially thought it as common roundation error but like you tested with VFP anyway. VFP5-8 returns it as a 0, C#, excel as that -2.7...E-17 value. Interestingly there are smaller numbers in float range close to 0.
>
>Thanks:)
>Cetin

Hi Cetin,

This might explain to why it is happening. As you see the value is -2.7..E-17 is because a floating point of Double data-type has maximum limit of 8-bytes = 64 bits = 16 digits only. In the old version of C, there is a Long Double (= max FPU size = 10 bytes), they drop this capability in the newer version of C/C++ (I don't know exactly what version it was dropped). In the new version the Long Double has been Casting into Double only. So, you can only work around this 64-bits limitation.

So, if you type this in excel: =ROUND( 1*(0.5 - 0.4 - 0.1), 16 ) it will give you 0.
I think VFP already use this workaround internally.

Now, this one is interesting. Because of that limitation, if you type a number (with no decimal point) longer than 16 digits both VFP and Excel will return different results and they both incorrect <g>.
Try this:

x = 45036172356878295
?x
x = 15036172356878295
?x
x=117346456767843354
?x

Btw, CONGRATULATIONS for you :-))
Regards