Binary rounding error. Because data is stored in binary
code in a computer there are certain decimal values that
don't quite work out properly when you perform
mathematical operations on them. Binary is inherently a
bad numbering system because it can really only handle
integer values well. In fact, it's so bad that:

64.1-64=0.999999999999943
64.2-64=0.200000000000003
64.3-64=0.299999999999997
64.4-64=0.400000000000006
64.5-64=0.5 (Hey, this one works!)
64.6-64=0.599999999999994
64.7-64=0.700000000000003
64.8-64=0.799999999999997
64.9-64=0.900000000000006

-----Original Message-----
Strange strange... look at this simple excel-VBA code

Sub test()
Dim tempRound As Double
Dim tempInt, tempDec As Double
Dim number As Double
number = 64.1

tempRound = Round(number, 1)
tempInt = Int(tempRound)
tempDec = (10 * (tempRound - tempInt))

Debug.Print "tempRound = " & tempRound
Debug.Print "tempInt = " & tempInt
Debug.Print "tempDec = " & tempDec

End Sub

Ok this code is supposed to have the integer part
of "number" in the "tempInt" variable (ie tempInt=64) and
the decimal part rounded to the first decimal value in
the "tempDec" variable (ie tempDec=1).
BUT it outputs:

tempRound = 64.1
tempInt = 64
tempDec = 0.999999999999943

Hmmm anything wrong here perhaps!!!!
Any comment?!?
Karl
.

You're not serious are you? You mean, as I know the
difference will be 0.1, I should round the wrong result
from the calculation so that it fits 0.1 !!!???

Btw, I'm using this value as a seed for a filename, and
I'm happier if my file is called:
64_1.txt and not
64_0.999999999999946.txt ;-)

I guess you have to be VERY careful with numbers in VB...
Karl
oh, and C++ does it right! (see my answer to your 1st post)

-----Original Message-----
How to write 64.1-64 and get EXACTLY 0.1 ? (that must be
possible in VB or not?)

Why? The deviation we are talking about here is of the
same order as 1 cm compared to the distance between the
earth and the sun. If you do not want to see the mess
caused by the calculations, round the result to the
desired number of decimals.
.

Final remark:

That C++ does it wrong in this case does not mean that the
outcome of a floating point operation is, in general,
exact. It is not. In no compiler. Ever.

Anyway, there are simpler ways of replacing the decimal .
by an underscore.

As about the ignoring rounding errors (or making them fit,
as you call it): suppose we were dealing with money, why
would rounding the results to 2 decimals be so bad? I
don't know about you, but I can spare 5.7e-12 cents any
time.

-----Original Message-----
You're not serious are you? You mean, as I know the
difference will be 0.1, I should round the wrong result
from the calculation so that it fits 0.1 !!!???

Btw, I'm using this value as a seed for a filename, and
I'm happier if my file is called:
64_1.txt and not
64_0.999999999999946.txt ;-)

I guess you have to be VERY careful with numbers in VB...
Karl
oh, and C++ does it right! (see my answer to your 1st
post)

-----Original Message-----
How to write 64.1-64 and get EXACTLY 0.1 ? (that must
be
possible in VB or not?)

Why? The deviation we are talking about here is of the
same order as 1 cm compared to the distance between the
earth and the sun. If you do not want to see the mess
caused by the calculations, round the result to the
desired number of decimals.
.

.

Thanks for your answers anyway.
Best regards
Karl
-----Original Message-----
Final remark:

That C++ does it wrong in this case does not mean that
the
outcome of a floating point operation is, in general,
exact. It is not. In no compiler. Ever.

Anyway, there are simpler ways of replacing the decimal .
by an underscore.

As about the ignoring rounding errors (or making them
fit,
as you call it): suppose we were dealing with money, why
would rounding the results to 2 decimals be so bad? I
don't know about you, but I can spare 5.7e-12 cents any
time.

-----Original Message-----
You're not serious are you? You mean, as I know the
difference will be 0.1, I should round the wrong result
from the calculation so that it fits 0.1 !!!???

Btw, I'm using this value as a seed for a filename, and
I'm happier if my file is called:
64_1.txt and not
64_0.999999999999946.txt ;-)

I guess you have to be VERY careful with numbers in VB...
Karl
oh, and C++ does it right! (see my answer to your 1st
post)

-----Original Message-----
How to write 64.1-64 and get EXACTLY 0.1 ? (that must
be
possible in VB or not?)

Why? The deviation we are talking about here is of the
same order as 1 cm compared to the distance between the
earth and the sun. If you do not want to see the mess
caused by the calculations, round the result to the
desired number of decimals.
.

.

.