problem with decimals

[V23]

Why

7.04 - 7 = 0.04

and

8.04 - 8 = 0.0399999999999991

???

I not found the answer of problem in forum.

Please help me.

[mmavipc]

Why

7.04 - 7 = 0.04

and

8.04 - 8 = 0.0399999999999991

???

I not found the answer of problem in forum.

Please help me.

hmmm. i'm posing a bug report

edit:http://www.autoitscript.com/trac/autoit/ticket/716

Edited December 1, 2008 by mmavipc

[V23]

hmmm. i'm posing a bug report

edit:http://www.autoitscript.com/trac/autoit/ticket/716

heh. I'm too. (#715)

but the real cool man told me

"It NOT a bug, you should try to ask in forum"

and deleted my report... =\

[cppman]

It isn't a bug. It is an error with floating-point values.

Edited December 1, 2008 by cppman

[V23]

It isn't a bug. It is an error with floating-point values.

Could you tell me more in detail, please?

[cppman]

Could you tell me more in detail, please?

Floating-point values (decimals) are prone to being inaccurate. The more precise (the more numbers behind the decimal) the more of a chance the value will be inaccurate. AutoIt, internally, uses a double to store floating-point values. Since a double can store more decimal places than a 'float', there is more of a chance the value will be inaccurate. If you can see the real values of some floating-point values before some operation is done to them, you'll see a lot of them are inaccurate.

Here's an example of the same problem in C++:

[V23]

Floating-point values (decimals) are prone to being inaccurate. The more precise (the more numbers behind the decimal) the more of a chance the value will be inaccurate. AutoIt, internally, uses a double to store floating-point values. Since a double can store more decimal places than a 'float', there is more of a chance the value will be inaccurate. If you can see the real values of some floating-point values before some operation is done to them, you'll see a lot of them are inaccurate.

Here's an example of the same problem in C++:

Thank you very much!

I think I understood.

[Valik]

http://www.autoitscript.com/forum/index.php?showtopic=18684

[charvi]

Yes, floating point values are inaccurate. Because I was not aware of this before, I had a real headache when I discovered it for the first time with another programming language

The solution is to always use a formatted string for the outputs. Or, you can round the number first.

$i = 8.04 - 8
$f = StringFormat("%.14f",$i)
$r = Round($i,14)
MsgBox(0, "Format Number", $i & @LF & $f & @LF & $r)

And to be most accurate, you should take only the 14 first SIGNIFICANT digits. This means that when you have 1 digit before the decimal point, get the first 13 digits after the decimal point. If you have 2 digits before the decimal point, take the first 12 digits after the decimal point, and so on.

[V23]

yes, realy thanx everybody for info!

I'v got the point)

[trancexx]

yes, realy thanx everybody for info!

I'v got the point)

You mean... floating-point.