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https://issues.apache.org/jira/browse/MATH-1397?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15986132#comment-15986132
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Wilhelm Burger commented on MATH-1397:
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I am not sure what the status of this issue is (apparently has been unsolved
for years), but this is an URGENT PROBLEM and should be fixed soon!
I told my students to use a "proven" libary instread of doing their own
implementation of 'Complex' and the first thing they run across is this bug.
What should I tell them now? Surprisingly, the (NaN, NaN) outcome is intended
(even checked in a test case!), although I do not know of any other environment
with a similar behaviour.
Why is the pow() based on the log() in the first place? Wouldn't it be simpler
to perform exponentiation in polar form, without the 0-singularity?
--Wilhelm
> Complex.ZERO.pow(2.0) is NaN
> ----------------------------
>
> Key: MATH-1397
> URL: https://issues.apache.org/jira/browse/MATH-1397
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.6.1
> Environment: Linux, Java1.7/Java1.8
> Reporter: Mario Wenzel
> Assignee: Eric Barnhill
> Priority: Minor
> Fix For: 4.0
>
>
> ```
> package complextest;
> import org.apache.commons.math3.complex.Complex;
> public class T {
> public static void main(String[] args) {
> System.out.println(Complex.ZERO.pow(2.0));
> }
> }
> ```
> This is the code and the readout is `(NaN, NaN)`. This surely isn't right.
> For one, it should actually be zero
> (https://www.wolframalpha.com/input/?i=(0%2B0i)%5E2) and second of all, the
> documentation doesn't state that anything could go wrong from a Complex
> number that has no NaNs and Infs.
> The other definition states that it doesn't work when the base is Zero, but
> it surely should. This strange corner case destroys any naive implementation
> of stuff wrt the mandelbrot set.
> It would be nice to not have to implement this exception myself.
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