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| Re: compare float numbers with precision [message #486326 is a reply to message #486305] |
Thu, 17 September 2009 09:38   |
 Daniel Krügler
Messages: 853
Registered: July 2009 |
Senior Member |
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Stella wrote:
> Hi, in my rcp I need a way to compare files with floating numbers with
> certain precision, i.e. if difference between numbers in some place is
> less than precision value - don't show the difference. What is the
> simplest way to do it? I looked to org.eclipse.compare plugin, I don't
> find extension point to change a way to calculate difference.
> Any suggestions for the way to do it? Thanks, Stella
Please define "simple". The most simple approach is e.g. an
implemention Comparator#compare with an absolute threshold:
public class AbsToleranceComparator implements Comparator<Double> {
private final double threshold;
public AbsToleranceComparator(double threshold) {
assert threshold >= 0;
this.threshold = threshold;
}
@Override
public int compare(Double o1, Double o2) {
double diff = o1 - o2;
return Math.abs(diff) < threshold ? 0 :
Double.compare(diff, 0.0);
}
}
This is "simple", but it does not properly consider null values,
overflow, NaNs and Infs. It has only a special use-case, where
absolute differences are correct, but that doesn't mean that
this is your use-case. I know many use-cases, which would be e.g.
be based on a relative difference criterion, where maybe support
for nullable values or maybe for infinities and NaNs requires
special handling.
HTH & Greetings from Bremen,
Daniel Krügler
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