Why (-0.7 + 0.4) - (-0.3) is not 0 ?

[cactus]

Is it a bug? How can I avoid such problems when I use ">0" or "<0"?

My version is 7.0 and the vi is programmed in WinXP.

Thank you !

[becktho]

Hi cactus

No, this is not a bug. This has to do with the management of floating point numbers in a computer.

Refer to this threads:

http://forums.ni.com/ni/board/message?board.id=170&message.id=102839&query.id=2735#M102839

http://forums.ni.com/ni/board/message?board.id=170&message.id=152289&query.id=2749#M152289

Hope this helps.

Thomas

[chilly_charly]

Roughly said, 0.7, 0.4 and 0.3 are not round numbers when expressed in the binary system. Your question can be translated as :

why 1 - 0.6666 - 0.3333 is not equal to 0 ?

This was one of the very first things that were taught one generation ago to students learning computer programming ;). I'm not sure if this is still the case nowaday, since this question appears quite often on this forum. 😄

[becktho]

It is still this case nowadays. At least 4 years ago at the school I went to ;).

Thomas

[Henrik_Volkers]

You can use the in Range and coerce vi and define your range of the region around 0 that fit your needs. Another way is to look for a change in the sign.

Don't mix up calculations (with uncertancy) and math

You just learned by 'DOING'  (sound of a head hitting the door)