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From Phil Steitz <phil.ste...@gmail.com>
Subject Re: [jira] Issue Comment Edited: (MATH-475) MathUtils.equals(double, double, double) does not agree with Javadoc
Date Sun, 16 Jan 2011 02:01:19 GMT
On Sat, Jan 15, 2011 at 8:32 PM, Gilles Sadowski
<gilles@harfang.homelinux.org> wrote:
> Hi.
>
> On Sat, Jan 15, 2011 at 12:48:45PM -0500, Phil Steitz (JIRA) wrote:
>>
>>     [ https://issues.apache.org/jira/browse/MATH-475?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12982118#action_12982118
]
>>
>> Phil Steitz edited comment on MATH-475 at 1/15/11 12:48 PM:
>> ------------------------------------------------------------
>>
>> Very interesting example.  How do you come up with this stuff, Sebb?  :)
>>
>> I tend to agree with Gilles' view that if if a and b are not distinguishable as doubles,
we don't really have any confidence in the value of abs(a - b), so the short-circuit in the
current code is better.  I would say just update the javadoc to make say something like
>>
>> "Returns true if the values are indistinguishable as doubles or the difference between
them is within the range of allowed error (inclusive)."
>>
>>       was (Author: psteitz):
>>     Very interesting example.  How do you come up with this stuff, Sebb?  :)
>>
>> I tend to agree with Gilles' view that if if a and b are not distinguishable as doubles,
we don't really have any confidence in the value of abs(a - b), so the short-circuit in the
current code is better.  I would say just update the javadoc to make say something like
>>
>> "Returns true if there is no double value strictly between the arguments or the difference
between them is within the range of allowed error (inclusive)."
>
> Just to be sure that we agree on the semantics of "equals": The latter
> description ("there is no double value strictly between the arguments")
> seems more representative of the code. Indeed, 2 successive floating point
> numbers _are_ distinguishable, but "equals" will nevertheless return true on
> the ground that any real number within the interval could be mapped to
> either of the two floating point numbers.
>
Sorry I got the second version of the comment wrong.  You are right
that the current impl of equals identifies two consecutive doubles.

Phil

>
> Gilles
>
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