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Date: Mon, 10 May 2010 06:14:48 -0400 (EDT)
From: "Gilles (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
Subject: [jira] Commented: (MATH-370) NaN in "equals" methods
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    [ https://issues.apache.org/jira/browse/MATH-370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12865720#action_12865720 ] 

Gilles commented on MATH-370:
-----------------------------

Well, the first impression I got from looking at those methods in "MathUtils" was indeed that they provide the "right" way to compare primitive doubles. Now, the right way for most users dealing with numerical codes should arguably be IEEE754-compliant.  So, unless we can explain that the way CM handles NaN is somehow more useful than what the IEEE standard defines, CM should at least provide "equals" utility methods that stick to the standard.
I understand the usefulness of the current implementation in the examples which you gave, but as a matter of principle this usage is second in priority (from a user perspective): it is mainly internal to CM.
Maybe, we should create a "util.internal" package where (CM) developer-utilities methods would live, whereas "util" would contain the functions which users are most likely looking for.  I think that it would be clearer (e.g. it would avoid dealing with long names such as "equalsIncludingNaN").  What do you think?


> NaN in "equals" methods
> -----------------------
>
>                 Key: MATH-370
>                 URL: https://issues.apache.org/jira/browse/MATH-370
>             Project: Commons Math
>          Issue Type: Bug
>            Reporter: Gilles
>            Priority: Minor
>
> In "MathUtils", some "equals" methods will return true if both argument are NaN.
> Unless I'm mistaken, this contradicts the IEEE standard.
> If nobody objects, I'm going to make the changes.

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