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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;


/**
 * A view of a {@link IntegerVector} that that allows the backing data to be
 * resized and also viewed from an offset.  Furthermore, this class allows the
 * viewed data to be immutable, where all mutating operations throw {@link
 * UnsupportedOperationException}.
 *
 * 
 *
 * Note that the original {@code IntegerVector} may still be altered even if
 * this view is marked as immutable.
 *
 * @author Keith Stevens
 * @author David Jurgens
 */
class IntegerVectorView extends VectorView implements IntegerVector {

    private static final long serialVersionUID = 1L;

    /**
     * A {@link IntegerVector} reference to the backing vector
     */
    protected final IntegerVector intVector;

    /**
     * Creates a new {@link IntegerVector} view of the data in the provided
     * {@link IntegerVector}.
     *
     * @param v the {@code IntegerVector} to view as containing double data.
     */
    public IntegerVectorView(IntegerVector v) {
        this(v, 0, v.length(), false);
    }

    /**
     * Creates a new, optionally immutable {@link IntegerVector} view of the
     * data in the provided {@link IntegerVector}.
     *
     * @param v the {@code IntegerVector} to view as containing double data.
     * @param isImmutable {@code true} if this view should not allow mutating
     *        operations to change the state of the backing vector
     */
    public IntegerVectorView(IntegerVector v, boolean isImmutable) {
        this(v, 0, v.length(), isImmutable);
    }

    /**
     * Creates a new {@link IntegerVector} sub-view of the data in the provided
     * {@link IntegerVector} using the offset and length to specify a viewing
     * region.
     *
     * @param v the {@code Vector} to decorate.
     * @param offset the index at which values of {@code v} are stored in this
     *               {@code ViewIntegerAsIntegerVector}.
     * @param length the maximum length of this {@code
     *               ViewIntegerAsIntegerVector}.
     */
    public IntegerVectorView(IntegerVector v, int offset, int length) {
        this(v, offset, length, false);
    }

    /**
     * Creates a new, optionally immutable {@link IntegerVector} sub-view of the
     * data in the provided {@link IntegerVector} using the offset and length to
     * specify a viewing region.
     *
     * @param v the {@code Vector} whose data is reflected in this view.
     * @param offset the index of {@code v} at which the first index of this
     *               view starts
     * @param length the length of this view.
     * @param isImmutable {@code true} if this view should not allow mutating
     *        operations to change the state of the backing vector.
     */
    public IntegerVectorView(IntegerVector v, int offset, int length, 
                                 boolean isImmutable) {
        super(v, offset, length, isImmutable);
        intVector = v;
    }

    /**
     * {@inheritDoc}
     */
    public int add(int index, int delta) {
        if (isImmutable) 
            throw new UnsupportedOperationException(
                "Cannot modify an immutable vector");
        return intVector.add(getIndex(index), delta);
    }

    /**
     * {@inheritDoc}
     */
    public void set(int index, int value) {
        if (isImmutable) 
            throw new UnsupportedOperationException(
                "Cannot modify an immutable vector");
        intVector.set(getIndex(index), value);
    }

    /**
     * {@inheritDoc}
     */
    public int get(int index) {
        return intVector.get(getIndex(index));
    }

    /**
     * {@inheritDoc}
     */
    public Integer getValue(int index) {
        return intVector.get(getIndex(index));
    }

    /**
     * {@inheritDoc}
     */
    @Override public double magnitude() {
        // Check whether the current magnitude is valid and if not, recompute it
        if (magnitude < 0) {
            double m = 0;
            for (int i = vectorOffset; i < vectorOffset + vectorLength; ++i) {
                int j = intVector.get(i);
                m += j * j;
            }
            magnitude = Math.sqrt(m);
        }
        return magnitude;
    }

    /**
     * {@inheritDoc}
     */
    public int[] toArray() {
        if (vectorOffset > 0 || vectorLength != vector.length()) {
            int[] r = new int[vectorLength - vectorOffset];
            for (int i = vectorOffset; i < vectorLength; ++i)
                r[i] = intVector.get(i);
            return r;
        }
        else
            return intVector.toArray();
    }
}