Groups > comp.lang.java.programmer > #35820

Re: double == double

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From	Eric Sosman <esosman@comcast-dot-net.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: double == double
Date	Wed, 19 Oct 2016 09:32:35 -0400
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On 10/19/2016 9:03 AM, Mike Amling wrote:
> 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);
> }

     This would return +0.0 for max(-0.0, -0.0).

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

Thread

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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