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https://issues.apache.org/jira/browse/MATH-313?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12771647#action_12771647
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Luc Maisonobe commented on MATH-313:
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I strongly disagree with this proposal.
UnivariateRealFunction is a very basic interface and used in many place, for
exemple in root solvers.
Almost all uses I have seen for the interface are people declaring their
existing class implements it only to be able to use it in a solver. These users
class may already belong to a class hierarchy. Java does not support multiple
inheritance (which is a good thing), so in many rxisting use cases (in fact all
the cases I have seen myself) extending the class would be a real problem.
> Functions could be more object-oriented without losing any power.
> -----------------------------------------------------------------
>
> Key: MATH-313
> URL: https://issues.apache.org/jira/browse/MATH-313
> Project: Commons Math
> Issue Type: New Feature
> Affects Versions: 2.0
> Environment: all
> Reporter: Jake Mannix
> Fix For: 2.1
>
>
> UnivariateRealFunction, for example, is a map from R to R. The set of such
> functions has tons and tons of structure: in addition to being an algebra,
> equipped with +,-,*, and scaling by constants, it maps the same space into
> itself, so it is composable, both pre and post.
> I'd propose we add:
> {code}
> UnivariateRealFunction plus(UnivariateRealFunction other);
> UnivariateRealFunction minus(UnivariateRealFunction other);
> UnivariateRealFunction times(UnivariateRealFunction other);
> UnivariateRealFunction times(double scale);
> UnivariateRealFunction preCompose(UnivariateRealFunction other);
> UnivariateRealFunction postCompose(UnivariateRealFunction other);
> {code}
> to the interface, and then implement them in an
> AbstractUnivariateRealFunction base class. No implementer would need to
> notice, other than switching to extend this class rather than implement
> UnivariateRealFunction.
> Many people don't need or use this, but... it makes for some powerfully easy
> code:
> {code}UnivariateRealFunction gaussian =
> Exp.preCompose(Negate.preCompose(Pow2));{code}
> which is even nicer when done anonymously passing into a map/collect method
> (a la MATH-312).
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