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