Groups > comp.lang.java.programmer > #35818

Re: double == double

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From	Mike Amling <mamling@chaff.us>
Newsgroups	comp.lang.java.programmer
Subject	Re: double == double
Date	Wed, 19 Oct 2016 08:03:17 -0500
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On 10/12/16 7:15 AM, Stefan Ram wrote:
>   Sometimes it is taught that it makes no sense to compare
>   two double values with »==«.
>
>   But what about this function?
>
> public static double max( final double a, final double b)
> { return
>   a == 0.0 && b == 0.0 && java.lang.Double.doubleToRawLongBits( a )
>   == Double.doubleToRawLongBits( -0.0d )? b : a >= b ? a : b; }
>
>   which tries to return positive zero if one argument is
>   positive zero and the other one negative zero?
>
>   It seems that there are special cases when a comparison
>   of double values with »==« is appropriate. I have observed
>   that this is usually the case when comparing with »0.0« -
>   another example would be avoiding to divide by 0.0.

If a==0.0 and b==0.0, there's no need to test whether either is -0.0. 
The function could be simplified to

public static double max(final double a, final double b) {
   return a==0.0 && b==0.0 ? 0.0 : (a>=b ? a : b);
}

--Mike Amling
V2h5IHVzZSBvbmUgJ2phdmEubGFuZy5Eb3VibGUnIGFuZCBvbmUgJ0RvdWJsZSc/

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Re: double == double Mike Amling <mamling@chaff.us> - 2016-10-19 08:03 -0500
  Re: double == double Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-10-19 09:32 -0400
    Re: double == double Jerry Stuckle <jstucklex@attglobal.net> - 2016-10-19 10:26 -0400
      Re: double == double Jake Jarvis <pig_in_shoes@yahoo.com> - 2016-10-19 16:36 +0200
        Re: double == double Jerry Stuckle <jstucklex@attglobal.net> - 2016-10-19 16:50 -0400
          Re: double == double Jake Jarvis <pig_in_shoes@yahoo.com> - 2016-10-20 01:08 +0200
            Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-19 21:16 -0400
              Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-19 21:19 -0400
              Re: double == double Jerry Stuckle <jstucklex@attglobal.net> - 2016-10-19 21:47 -0400
                Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-19 21:52 -0400
    Re: double == double Michael Jung <miju@golem.phantasia.org> - 2016-10-19 19:39 +0200
    Re: double == double Mike Amling <mamling@chaff.us> - 2016-10-22 07:15 -0500

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