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https://issues.apache.org/jira/browse/MATH-1284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15983793#comment-15983793
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Raymond DeCampo commented on MATH-1284:
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Please take a look at the {{feature-MATH-1284}} branch.
First, I made it so that {{Vector}} no longer extends {{Point}}. Then I added
the appropriate methods from the {{Point}} interface to the {{Vector}}
interface.
The only implementations which represented problems were the {{Vector?D}}
classes. I noticed that the existing code dealing with these implementations
relied pretty heavily on casting back and forth between {{Point}} and
{{Vector}}, so the most prudent thing seemed to be supplying a class which
implements both.
I decided on {{Coordinates?D}} for the "new" classes (these are really just
{{Vector?D}} renamed). Here I am using the fact that point a vector and a
point in finite dimensional Euclidean space can be represented by a set of
coordinates. (Keeping the classes with {{Vector?D}} name would feel like we
hadn't really addressed the issue.)
If it is a problem that the {{Vector?D}} classes are just dropped we could
introduce them as an intermediate interface (or even as a concrete class which
{{Coordinates?D}} extends but that feels less satisfying).
Having {{Coordinates?D}} implement both interfaces led to some method calls
being ambiguously defined. Here I just removed one of the methods. I am
thinking now it would have been better just to create an implementation
accepting the {{Coordinate?D}} class.
In any case, there would be more work in terms of cleaning up and
documentation, this is not meant to be a finished product but a basis for
discussion.
> Vector is-not-a Point
> ---------------------
>
> Key: MATH-1284
> URL: https://issues.apache.org/jira/browse/MATH-1284
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.5
> Reporter: Roman Werpachowski
> Priority: Minor
> Fix For: 4.0
>
>
> The class hierarchy for geometry claims that Vector is-a Point:
> https://commons.apache.org/proper/commons-math/apidocs/org/apache/commons/math3/geometry/Point.html
> This is mathematically incorrect, see e.g.
> http://math.stackexchange.com/a/645827
> Just because they share the same numerical representation, Point and Vector
> shouldn't be crammed into a common class hierarchy.
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