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https://issues.apache.org/jira/browse/MATH-535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13000601#comment-13000601
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Gilles commented on MATH-535:
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In the end, I don't think that these methods are useful. Within the current
code, all they would do is hide a constructor call. In the case of
"createParametric()" the returned object would not be very interesting: e.g. a
caller that would treat it as a "ParametricUnivariateRealFunction" would not
know how many parameters are needed to call "value(double x, double[] param)".
So, unless someone sees a real usefulness, I'm going to close this issue.
> Closing the loop in function objects
> ------------------------------------
>
> Key: MATH-535
> URL: https://issues.apache.org/jira/browse/MATH-535
> Project: Commons Math
> Issue Type: New Feature
> Reporter: Gilles
> Priority: Minor
> Labels: api-change
> Fix For: 3.0
>
>
> Some function classes (in package "analysis.function") now contains a
> "Parametric" inner class that provides a parametric version of the function
> represented by the enclosing class.
> # We could enhance the "UnivariateRealFunction" interface to contain:
> {noformat}
> public ParametricUnivariateRealFunction createParametricFunction();
> {noformat}
> which, e.g. for the "Gaussian" concrete class, would translate to:
> {noformat}
> public Gaussian.Parametric createParametricFunction() {
> return new Gaussian.Parametric();
> }
> {noformat}
> # We could enhance the "ParametricUnivariateRealFunction" interface to
> contain:
> {noformat}
> public UnivariateRealFunction createFunction(double[] param);
> {noformat}
> which, in "Gaussian.Parametric", would translate to:
> {noformat}
> public Gaussian createFunction(double[] param) {
> validateParameters(param);
> return new Gaussian(param[0], param[1], param[2]);
> }
> {noformat}
> In both cases, it would allow programming against interfaces.
> For the first case, not all current implementations of
> "UnivariateRealFunction" provide a "Parametric" version (and for most there
> are no parameters). So either we create a new
> "AbstractUnivariateRealFunction" that provides a default implementation of
> "createParametricFunction" (throwing an exception) and make all current
> function classes extends this one, or we create a new interface (something
> like "ParametricFactory") that declares the new "createParametricFunction()"
> and add the "implements ParametricFactory" clause to any class that provides
> a parametric version.
> I think that the latter is the cleanest. Or is there still another
> possibility?
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