[jira] [Created] (MATH-1522) The generic parameter of ClusterRanking can be move to method

["Chen Tao (Jira)" <ji...@apache.org>]

Chen Tao created MATH-1522:
------------------------------

             Summary: The generic parameter of ClusterRanking can be move to method
                 Key: MATH-1522
                 URL: https://issues.apache.org/jira/browse/MATH-1522
             Project: Commons Math
          Issue Type: Improvement
            Reporter: Chen Tao


The generic parameter on class "ClusterRanking“ is unnecessary, 
it is redundancy on define a variable, and hard to reuse(it could be):

{code:java}
ClusterRanking<DoublePoint> evaluator = new SumOfClusterVariances<>();
List<Cluster<DoublePoint>> clusters1 = ...
evaluator.compute(clusters1); // It is OK.
...
// It could be reused globally, but now trigger a compile error
List<Cluster<MyClusterable>> clusters2 = ...
evaluator.compute(clusters2); // Compile error
{code}


The generic parameter of ClusterRanking can be move to method: 
{code:java}
@FunctionalInterface
public interface ClusterRanking {
    /**
     * Computes the rank (higher is better).
     *
     * @param clusters Clusters to be evaluated.
     * @return the rank of the provided {@code clusters}.
     */
    <T extends Clusterable> double compute(List<? extends Cluster<T>> clusters);
}
{code}

Then we can define a ClusterRanking easier and reuse it globally:
{code:java}
// The variable define is simple now.
ClusterRanking evaluator = new SumOfClusterVariances();
...
List<Cluster<DoublePoint>> clusters1 = ...
double score1 = evaluator.compute(clusters1); // OK.
...
// It can be reused globally now.
List<Cluster<MyClusterable>> clusters2 = ...
double score2 = evaluator.compute(clusters2); // OK.
{code}



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