/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.lucene.search.similarities;
import org.apache.lucene.search.Explanation;
/**
* The <em>lambda (λ<sub>w</sub>)</em> parameter in information-based
* models.
* @see IBSimilarity
* @lucene.experimental
*/
public abstract class Lambda {
/**
* Sole constructor. (For invocation by subclass
* constructors, typically implicit.)
*/
public Lambda() {}
/** Computes the lambda parameter. */
public abstract float lambda(BasicStats stats);
/** Explains the lambda parameter. */
public abstract Explanation explain(BasicStats stats);
/**
* Subclasses must override this method to return the code of the lambda
* formula. Since the original paper is not very clear on this matter, and
* also uses the DFR naming scheme incorrectly, the codes here were chosen
* arbitrarily.
*/
@Override
public abstract String toString();
}