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https://issues.apache.org/jira/browse/MATH-471?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12981807#action_12981807
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Sebb commented on MATH-471:
---------------------------
Many of the double-only methods work OK with widened float parameters.
Where this is not the case, we either need to fix the discrepancy (as per this
JIRA) or document the restriction.
I don't see the point of separating the utilities into two different classes,
but if the consensus is that we should, then we need to make sure that the same
methods are present in both, even if the double method works perfectly well,
otherwise it would be even more confusing for users (where do I find the
method?).
But I think the main issue is that having a separate class would force users to
*edit and recompile* to take advantage of any fixes such as this one.
> MathUtils.equals(double, double) does not work properly for floats
> ------------------------------------------------------------------
>
> Key: MATH-471
> URL: https://issues.apache.org/jira/browse/MATH-471
> Project: Commons Math
> Issue Type: Bug
> Reporter: Sebb
> Attachments: Math471.patch
>
>
> MathUtils.equals(double, double) does not work properly for floats.
> There is no equals(float,float) so float parameters are automatically
> promoted to double. However, that is not necessarily appropriate, given that
> the ULP for a double is much smaller than the ULP for a float.
> So for example:
> {code}
> double oneDouble = 1.0d;
> assertTrue(MathUtils.equals(oneDouble, Double.longBitsToDouble(1 +
> Double.doubleToLongBits(oneDouble)))); // OK
> float oneFloat = 1.0f;
> assertTrue(MathUtils.equals(oneFloat, Float.intBitsToFloat(1 +
> Float.floatToIntBits(oneFloat)))); // FAILS
> float f1 = 333.33334f;
> double d1 = 333.33334d;
> assertTrue(MathUtils.equals(d1, f1)); // FAILS
> {code}
> I think the equals() methods need to be duplicated with the appropriate
> changes for floats to avoid any problems with the promotion of floats.
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