io.jenetics.ext.moea.ElementDistance Maven / Gradle / Ivy
/*
* Java Genetic Algorithm Library (jenetics-8.1.0).
* Copyright (c) 2007-2024 Franz Wilhelmstötter
*
* Licensed 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.
*
* Author:
* Franz Wilhelmstötter ([email protected])
*/
package io.jenetics.ext.moea;
import java.util.function.Function;
import java.util.function.ToDoubleBiFunction;
/**
* Defines the distance of two elements of a given vector type {@code V}.
* The following example creates an {@code ElementDistance} function for a
* {@code double[] array}:
* {@snippet lang="java":
* final ElementDistance dist = (u, v, i) -> u[i] - v[i];
* }
*
* @param the vector type
*
* @author Franz Wilhelmstötter
* @version 4.1
* @since 4.1
*/
@FunctionalInterface
public interface ElementDistance {
/**
* Calculates the distance of two vector elements at the given {@code index}.
* E.g.
* {@snippet lang="java":
* final ElementDistance dist = (u, v, i) -> u[i] - v[i];
* }
*
* @param u the first vector
* @param v the second vector
* @param index the vector index
* @return the distance of the two element vectors
*/
double distance(final V u, final V v, final int index);
/**
* Return an element distance function for the mapped type {@code T}.
*
* @param mapper the mapper function
* @param the new distance type
* @return an element distance function for the mapped type {@code T}
*/
default ElementDistance
map(final Function mapper) {
return (u, v, i) -> distance(mapper.apply(u), mapper.apply(v), i);
}
/**
* Return a function which calculates the distance of two vector elements at
* a given {@code index}.
*
* @param index the vector index
* @return a function which calculates the distance of two vector elements
*/
default ToDoubleBiFunction ofIndex(final int index) {
return (u, v) -> distance(u, v, index);
}
}