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From "Gilles (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (MATH-632) NaN: Method "equals" in Complex not consistent with "==" for "double" primitive type
Date Fri, 05 Aug 2011 22:09:27 GMT

     [ https://issues.apache.org/jira/browse/MATH-632?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Gilles resolved MATH-632.
-------------------------

    Resolution: Not A Problem

Clarifying note added in revision 1154392.


> NaN: Method "equals" in Complex not consistent with "==" for "double" primitive type
> ------------------------------------------------------------------------------------
>
>                 Key: MATH-632
>                 URL: https://issues.apache.org/jira/browse/MATH-632
>             Project: Commons Math
>          Issue Type: Bug
>            Reporter: Gilles
>            Priority: Minor
>             Fix For: 3.0
>
>
> The following tests show several contradictions:
> {code}
> final double a = Double.NaN;
> final double b = Double.NaN;
> Assert.assertFalse("a == b", a == b); // (1)
> Assert.assertEquals("a != b", a, b, Double.MIN_VALUE); // (2)
> Assert.assertFalse("a == b", MathUtils.equals(a, b, Double.MIN_VALUE)); // (3)
> Assert.assertFalse("a == b", MathUtils.equals(a, b, Double.MIN_VALUE)); // (4)
> final Double dA = Double.valueOf(a);
> final Double dB = Double.valueOf(b);
> Assert.assertFalse("dA == dB", dA.doubleValue() == dB.doubleValue()); // (5)
> Assert.assertTrue("!dA.equals(dB)", dA.equals(dB)); // (6)
> final Complex cA = new Complex(a, 0);
> final Complex cB = new Complex(b, 0);
> Assert.assertTrue("!cA.equals(cB)", cA.equals(cB));  // (7)
> {code}
> They all pass; thus:
> # "Double" does not behave as "double": (1) and (5) vs (6)
> # Two NaNs are almost equal for Junit: (2)
> # Two NaNs are never equal for MathUtils: (3) and (4)
> # Complex.NaN is consistent with Object "Double.valueOf(NaN)" (hence not with primitive
"Double.NaN"): (7)
> This is quite confusing.
> In MathUtils, we chose to follow IEEE754 (and Java for primitive "double"), i.e. it is
"correct" that assertion (1) is false. Do we want "Complex" to conform with this or with the
inconsistent behaviour of "Double"?

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