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From "Wilhelm Burger (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-1397) Complex.ZERO.pow(2.0) is NaN
Date Thu, 27 Apr 2017 14:11:04 GMT

    [ https://issues.apache.org/jira/browse/MATH-1397?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15986684#comment-15986684
] 

Wilhelm Burger commented on MATH-1397:
--------------------------------------

Hello Gilles, thanks for your enlightening comments. I'd be happy to help if I can (i.e.,
add anything to the outstanding experts' work). I have seen the recent patch for the pow()
method by Raymond and wondered if there was an accessible (and complete) GIT repo for the
"Commons Numbers" project. I tried to build the subproject but could not find the associated
parent project (POM).

--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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