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https://issues.apache.org/jira/browse/GEOMETRY-23?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16665256#comment-16665256
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Matt Juntunen commented on GEOMETRY-23:
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bq. Implementation-wise, yes, but the API is wrong, because a vector is not a
set of Cartesian coordinates (the reverse is true).
No one is saying that a vector *is* a set of Cartesian coordinates. I would say
you have a point if we were discussing the generic {{Vector}} interface but
we're discussing concrete classes here. We've chosen (rightly so) to use
Cartesian coordinates to represent Euclidean vectors in our *primary* vector
implementation classes. We've also chosen the absolute simplest name for what
these concrete classes represent, eg {{Vector2D}}, a Euclidean vector in two
dimensions. Since we've chosen that {{Vector2D}} is represented by {{(x, y)}}
Cartesian coordinates, then our VALJO "valueOf" method should just accept those
arguments and set them directly. In other words, {{Vector2D.of(1, 2)}}, means
"give me a {{Vector2D}} with values 1 and 2." No conversion of the inputs is
required. For polar coordinates, a conversion *is* required, so we don't use a
"valueOf" method. Instead, we use {{fromPolar}} to indicate that a conversion
is taking place. (Here, I think the API does need to change since we currently
have {{ofPolar}}). I don't see how any of this is mathematically inaccurate or
misleading/confusing from an API perspective. Nothing in the API is preventing
the creation of {{PolarVector}} or {{BarycentricVector2D}} classes and their
use as vectors.
As far as the name {{Vector2D}} goes, there are plenty of precedents for
choosing a simple name to represent a specific implementation of something more
generic. For example, {{java.lang.String}} is not named
{{java.lang.UTF16String}} even though that would technically be more accurate.
Anyway, I just posted about this on the dev ML so hopefully we'll get some
other input soon.
> Remove Euclidean Point Classes
> ------------------------------
>
> Key: GEOMETRY-23
> URL: https://issues.apache.org/jira/browse/GEOMETRY-23
> Project: Apache Commons Geometry
> Issue Type: Improvement
> Reporter: Matt Juntunen
> Priority: Major
> Labels: pull-request-available
>
> Based on discussion of the current Point/Vector API in GEOMETRY-14 and
> research into other geometric libraries, I think we should remove the
> Euclidean Point?D classes and make Vector?D also implement Point. This will
> end up being similar to the previous commons-math design but avoids the issue
> raised in MATH-1284 since the Point and Vector interfaces are not related.
> They just happen to be implemented by the same class, which we're calling
> Vector?D since a vector can be used to indicate a point (by adding it to the
> origin).
> In the course of trying this out this design, I ended up removing 7 classes
> and simplifying several methods. I think that's a good indicator that this is
> a good design choice.
>
> Pull request: https://github.com/apache/commons-geometry/pull/15
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