Well, first of all, do realize that floating point number
representations are finite and therefore inexact. 0.4 decimal is an
infinite repeating fraction in binary. Although IEEE floating-point
includes guard bits and specific machinery to deal with this, it's
fairly easy to cause Java (or any other language) to reveal the
round-off error in the finite representation.
OK, so, look at the following line of Java code.
System.out.println(String.valueOf(new Double(Float.parseFloat("0.4"))));
It converts the String "0.4" into a float, constructs a double from
that float, then converts the Double into a String and displays
it. This line of Java -- note that this has nothing at all to do with
Jess! -- prints "0.4000000059604645" . The problem is that the float
has fewer significant digits than the double, so the lower accuracy
float shows up as the "...59604645" digits in the double.
If, on the other hand, you do this:
System.out.println(String.valueOf(Double.parseDouble("0.4")));
this line prints "0.4", as you'd expect.
Now, the Value constructor you're calling takes a double as an
argument, not a float, so what your code is doing below is very like
the first example: parse into a float, then convert to a double. Just
use double instead, and your "problem" should go away:
fInfo.setSlotValue("certainty", new
Value(Double.parseDouble((String) info.elementAt(2)), RU.FLOAT));
I think Ina Sollinger wrote:
[Charset iso-8859-1 unsupported, filtering to ASCII...]
> hi all,
>
> iam having a very "strange" problem:
>
> iam parsing values from java to jess by using:
>
> fInfo.setSlotValue("certainty", new
> Value(Float.parseFloat((String)info.elementAt(2)), RU.FLOAT));
>
> the info-vektor is a string vector, sometimes elements of the string are
> floats, therefore i chose the method Float.parseFloat.
>
> public Vector getInfo(String info){
> Vector v = new Vector();
> }else if(info.equals("occupation")){
> v.addElement(info);
> v.addElement("beamter");
> v.addElement("0.4"); /*<- (String)info.elementAt(2)
> v.addElement("");
> v.addElement("");
> v.addElement("");
>
> in jess the facts are "right" as long as info.elementAt(2) is 1, 0.5 or 0.
> However, if it is
> 0.4 (as in the example above) the fact in jess is 0.40000000596...
> or if it is 0.9 in the vector it becomes 0.89999999761 in Jess ?? !
>
> Can someone explain this behaviour?
> i really tried to change the 0.4 to 0.5 and it worked fine, but when i
> change the same number to something not 0.5 or 1 again, the values in jess become
> akward.???
>
> TKS,
>
> Ina
>
> --
> +++ GMX - Mail, Messaging & more http://www.gmx.net +++
> NEU: Mit GMX ins Internet. Rund um die Uhr f|r 1 ct/ Min. surfen!
>
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Ernest Friedman-Hill
Distributed Systems Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
Org. 8920, MS 9012 [EMAIL PROTECTED]
PO Box 969 http://herzberg.ca.sandia.gov
Livermore, CA 94550
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