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The S-Space Package is a Natural Language Processing library for distributional semantics representations. Distributional semantics representations model the meaning of words, phrases, and sentences as high dimensional vectors or probability distributions. The library includes common algorithms such as Latent Semantic Analysis, Random Indexing, and Latent Dirichlet Allocation. The S-Space package also includes software libraries for matrices, vectors, graphs, and numerous clustering algorithms.

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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.matrix;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOError;
import java.io.IOException;

import java.util.Iterator;
import java.util.NoSuchElementException;


/**
 * An iterator for sequentially accessing the data of a {@link
 * MatrixIO.Format.MATLAB_SPARSE} formatted file.
 */
class MatlabSparseFileIterator implements Iterator {

    private final BufferedReader matrixFileReader;

    private MatrixEntry next;

    /**
     * The line number for the matrix values that have just been read.
     */
    private int lineNo;

    public MatlabSparseFileIterator(File matrixFile) throws IOException {
        matrixFileReader = new BufferedReader(new FileReader(matrixFile));
        lineNo = 0;
        advance();
    }

    private void advance() throws IOException {
        String line = matrixFileReader.readLine();
        lineNo++;
        if (line == null) {
            next = null;
            // If the end of the file has been reached, close the reader
            matrixFileReader.close();
        }
        else {
            String[] rowColVal = line.split("\\s+");
            if (rowColVal.length != 3)
                throw new MatrixIOException(
                    "Incorrect number of values on line: " + lineNo);
            int row = Integer.parseInt(rowColVal[0]) - 1;
            int col = Integer.parseInt(rowColVal[1]) - 1;
            double value = Double.parseDouble(rowColVal[2]);
            next = new SimpleEntry(row, col, value);
        }
    }

    public boolean hasNext() {
        return next != null;
    }

    public MatrixEntry next() {
        if (next == null) 
            throw new NoSuchElementException("No futher entries");
        MatrixEntry me = next;
        try {
            advance();
        } catch (IOException ioe) {
            throw new IOError(ioe);
        }
        return me;
    }

    /**
     * Throws an {@link UnsupportedOperationException} if called.
     */
    public void remove() {
        throw new UnsupportedOperationException("Cannot remove from file");
    }
}