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Open-source Java libraries, supporting generalized smart arrays and matrices with elements of any types, including a wide set of 2D-, 3D- and multidimensional image processing and other algorithms, working with arrays and matrices.

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/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2007-2024 Daniel Alievsky, AlgART Laboratory (http://algart.net)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package net.algart.math.functions;

/**
 * Product from several numbers:
 * f(x₀, x₁, ..., x_n-1) =
 * scale*x₀x₁...x_n-1,
 * where scale is a constant, passed to {@link #getInstance(double)} method.
 * The {@link #get} method of the instance of this class may process any number of arguments.
 * If the number of arguments is 0, it returns scale value.
 *
 * This class is immutable and thread-safe:
 * there are no ways to modify settings of the created instance.
 *
 * @author Daniel Alievsky
 */
public final class MultiplyingFunc implements Func {
    private final double scale;

    private MultiplyingFunc(double scale) {
        this.scale = scale;
    }

    /**
     * Returns an instance of this class.
     *
     * @param scale the scale: additional constant multiplier.
     * @return an instance of this class.
     */
    public static MultiplyingFunc getInstance(double scale) {
        return new MultiplyingFunc(scale);
    }

    public double get(double... x) {
        double result = scale;
        for (double v : x) {
            result *= v;
        }
        return result;
    }

    public double get() {
        return scale;
    }

    public double get(double x0) {
        return scale * x0;
    }

    public double get(double x0, double x1) {
        return scale * x0 * x1;
    }

    public double get(double x0, double x1, double x2) {
        return scale * x0 * x1 * x2;
    }

    public double get(double x0, double x1, double x2, double x3) {
        return scale * x0 * x1 * x2 * x3;
    }

    /**
     * Returns a brief string description of this object.
     *
     * @return a brief string description of this object.
     */
    public String toString() {
        return "product function f(x0,x1,...)=" + scale + "*x0*x1*...";
    }
}