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The S-Space Package is a collection of algorithms for building Semantic Spaces as well as a highly-scalable library for designing new distributional semantics algorithms. Distributional algorithms process text corpora and represent the semantic for words as high dimensional feature vectors. This package also includes matrices, vectors, and numerous clustering algorithms. These approaches are known by many names, such as word spaces, semantic spaces, or distributed semantics and rest upon the Distributional Hypothesis: words that appear in similar contexts have similar meanings.

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/*
 * Copyright 2009 David Jurgens
 *
 * This file is part of the S-Space package and is covered under the terms and
 * conditions therein.
 *
 * The S-Space package is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation and distributed hereunder to you.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND NO REPRESENTATIONS OR WARRANTIES,
 * EXPRESS OR IMPLIED ARE MADE.  BY WAY OF EXAMPLE, BUT NOT LIMITATION, WE MAKE
 * NO REPRESENTATIONS OR WARRANTIES OF MERCHANT- ABILITY OR FITNESS FOR ANY
 * PARTICULAR PURPOSE OR THAT THE USE OF THE LICENSED SOFTWARE OR DOCUMENTATION
 * WILL NOT INFRINGE ANY THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER
 * RIGHTS.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see .
 */

package edu.ucla.sspace.vector;

import java.io.Serializable;

import java.util.Arrays;


/**
 * A {@code Vector} backed by a {@code double} array.  Any changes to the vector
 * are reflected in the backing array.  This class provides a link between
 * array-based and {@code Vector}-based computation.
 *
 * @author David Jurgens
*/
class DoubleArrayAsVector implements DoubleVector, Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * The array whose values back this vector
     */
    private final double[] array;

    /**
     * Creates a new vector back by the provided array
     *
     * @param vector the values of this vector
     */
    public DoubleArrayAsVector(double[] array) {
        assert array != null : "wrapped array cannot be null";
        this.array = array;
    }

    /**
     * {@inheritDoc}
     */
    public double add(int index, double delta) {
        return (array[index] += delta);
    }

    /**
     * {@inheritDoc}
     */
    public void set(int index, double value) {
        array[index] = value;
    }

    /**
     * {@inheritDoc}
     */
    public void set(int index, Number value) {
        array[index] = value.doubleValue();
    }

    /**
     * {@inheritDoc}
     */
    public double get(int index) {
        return array[index];
    }

    /**
     * {@inheritDoc}
     */
    public Double getValue(int index) {
        return array[index];
    }

    /**
     * {@inheritDoc}
     */
    public double magnitude() {
        double m = 0;
        for (double d : array)
            m += d * d;
        return Math.sqrt(m);
    }

    /**
     * {@inheritDoc}
     */
    public double[] toArray() {
        return Arrays.copyOf(array, array.length);
    }

    /**
     * {@inheritDoc}
     */
    public int length() {
        return array.length;
    }
}