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https://issues.apache.org/jira/browse/MATH-657?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13096572#comment-13096572
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Phil Steitz commented on MATH-657:
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This is probably best discussed on the mailing list before making changes to
contracts in the code.
There are two things going on here. First, this - possibly - represents
another case where the computational formula documented in the code returns NaN
and it an argument could be made that another value would be better. The
tradeoff is complexity in documentation and overhead in computation. I would
like to see a real practical use case justifying adding this overhead and added
complexity in both the code and javadoc.
The second question is more interesting. Again, decision should be based on
practical use cases. That question is, do we view our complex class as
representing the compactified space, including a designated single point at
infinity. One could argue that the answer is yes already, because we have
"INF" defined. But to really do this, we need to identify all of the other
infinite points (i.e., change equals) and also modify arithmetic operations
uniformly. I am not sure we really want to do that - first because of
performance impacts and second because some users may in fact want to preserve
directed infinities. I would like to hear from users and see actual use cases
justifying the changes before we walk down this path.
> Division by zero
> ----------------
>
> Key: MATH-657
> URL: https://issues.apache.org/jira/browse/MATH-657
> Project: Commons Math
> Issue Type: Bug
> Reporter: Gilles
> Assignee: Gilles
> Priority: Minor
> Fix For: 3.0
>
>
> In class {{Complex}}, division by zero always returns NaN. I think that it
> should return NaN only when the numerator is also {{ZERO}}, otherwise the
> result should be {{INF}}. See
> [here|http://en.wikipedia.org/wiki/Riemann_sphere#Arithmetic_operations].
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