Functions could be more object-oriented without losing any power.
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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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