Cell.java

/* ---------------------------------------------------------------------
 * Numenta Platform for Intelligent Computing (NuPIC)
 * Copyright (C) 2014, Numenta, Inc.  Unless you have an agreement
 * with Numenta, Inc., for a separate license for this software code, the
 * following terms and conditions apply:
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero Public License version 3 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Affero Public License for more details.
 *
 * You should have received a copy of the GNU Affero Public License
 * along with this program.  If not, see http://www.gnu.org/licenses.
 *
 * http://numenta.org/licenses/
 * ---------------------------------------------------------------------
 */

package org.numenta.nupic.model;

import java.io.Serializable;
import java.util.List;
import java.util.Set;

/**
 * Software implementation of a neuron in the neocortical region.
 * 
 * @author Chetan Surpur
 * @author David Ray
 */
public class Cell implements Comparable<Cell>, Serializable {
    /** keep it simple */
    private static final long serialVersionUID = 1L;
    
    /** This cell's index */
    private final int index;
    /** Remove boxing where necessary */
    final Integer boxedIndex;
    /** The owning {@link Column} */
    private final Column column;
    /** Cash this because Cells are immutable */
    private final int hashcode;
    

    /**
     * Constructs a new {@code Cell} object
     * @param column    the containing {@link Column}
     * @param colSeq    this index of this {@code Cell} within its column
     */
    public Cell(Column column, int colSeq) {
        this.column = column;
        this.index = column.getIndex() * column.getNumCellsPerColumn() + colSeq;
        this.boxedIndex = new Integer(index);
        this.hashcode = hashCode();
    }

    /**
     * Returns this {@code Cell}'s index.
     * @return
     */
    public int getIndex() {
        return index;
    }

    /**
     * Returns the column within which this cell resides
     * @return
     */
    public Column getColumn() {
        return column;
    }

    /**
     * Returns the Set of {@link Synapse}s which have this cell
     * as their source cells.
     *  
     * @param   c               the connections state of the temporal memory
     *                          return an orphaned empty set.
     * @return  the Set of {@link Synapse}s which have this cell
     *          as their source cells.
     */
    public Set<Synapse> getReceptorSynapses(Connections c) {
        return getReceptorSynapses(c, false);
    }

    /**
     * Returns the Set of {@link Synapse}s which have this cell
     * as their source cells.
     *  
     * @param   c               the connections state of the temporal memory
     * @param doLazyCreate      create a container for future use if true, if false
     *                          return an orphaned empty set.
     * @return  the Set of {@link Synapse}s which have this cell
     *          as their source cells.
     */
    public Set<Synapse> getReceptorSynapses(Connections c, boolean doLazyCreate) {
        return c.getReceptorSynapses(this, doLazyCreate);
    }

    /**
     * Returns a {@link List} of this {@code Cell}'s {@link DistalDendrite}s
     * 
     * @param   c               the connections state of the temporal memory
     * @param doLazyCreate      create a container for future use if true, if false
     *                          return an orphaned empty set.
     * @return  a {@link List} of this {@code Cell}'s {@link DistalDendrite}s
     */
    public List<DistalDendrite> getSegments(Connections c) {
        return getSegments(c, false);
    }

    /**
     * Returns a {@link List} of this {@code Cell}'s {@link DistalDendrite}s
     * 
     * @param   c               the connections state of the temporal memory
     * @param doLazyCreate      create a container for future use if true, if false
     *                          return an orphaned empty set.
     * @return  a {@link List} of this {@code Cell}'s {@link DistalDendrite}s
     */
    public List<DistalDendrite> getSegments(Connections c, boolean doLazyCreate) {
        return c.getSegments(this, doLazyCreate);
    }
    
    /**
     * {@inheritDoc}
     */
    public String toString() {
        return String.valueOf(index);
    }

    /**
     * {@inheritDoc}
     * 
     * <em> Note: All comparisons use the cell's index only </em>
     */
    @Override
    public int compareTo(Cell arg0) {
        return boxedIndex.compareTo(arg0.boxedIndex);
    }

    @Override
    public int hashCode() {
        if(hashcode == 0) {
            final int prime = 31;
            int result = 1;
            result = prime * result + index;
            return result;
        }
        return hashcode;
    }

    @Override
    public boolean equals(Object obj) {
        if(this == obj)
            return true;
        if(obj == null)
            return false;
        if(getClass() != obj.getClass())
            return false;
        Cell other = (Cell)obj;
        if(index != other.index)
            return false;
        return true;
    }
    
}