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
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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