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From "Eric Barnhill (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (NUMBERS-22) Method reciprocal() in Complex for complex numbers with parts very close to 0.0
Date Thu, 07 Sep 2017 13:20:00 GMT

    [ https://issues.apache.org/jira/browse/NUMBERS-22?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16156940#comment-16156940
] 

Eric Barnhill commented on NUMBERS-22:
--------------------------------------

The method now produces the standard result of -Infinity, 0.

> Method reciprocal() in Complex for complex numbers with parts very close to 0.0
> -------------------------------------------------------------------------------
>
>                 Key: NUMBERS-22
>                 URL: https://issues.apache.org/jira/browse/NUMBERS-22
>             Project: Commons Numbers
>          Issue Type: Improvement
>            Reporter: Gunel Jahangirova
>            Priority: Minor
>             Fix For: 1.0
>
>
> I have been redirected here from the issue repository of Apache Commons Math, as the
Complex class will likely be deprecated in favour of its equivalent in "Commons Numbers".
> In class Complex method reciprocal() returns INF only if the real and imaginary parts
are exactly equal to 0.0. In the cases when real and imaginary parts are double numbers very
close to 0.0, it does not hold. For example, if we run this code
> {code}
> Complex complex0 = new Complex((-2.44242319E-315));
> Complex complex1 = complex0.reciprocal();
> {code}
> the value of complex1.getReal() will be -Infinity and the value of complex1.getImaginary()
will be NaN, instead of complex1 being equal to INF.
> The suggested solutions after the discussion are either checking the equality to ZERO
with some tolerance or to detect if one of the real or imaginary parts is going to be infinite
or NaN and then return the proper result. 



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