001/* An actor that outputs a random sequence of booleans.
002
003 Copyright (c) 1998-2014 The Regents of the University of California.
004 All rights reserved.
005 Permission is hereby granted, without written agreement and without
006 license or royalty fees, to use, copy, modify, and distribute this
007 software and its documentation for any purpose, provided that the above
008 copyright notice and the following two paragraphs appear in all copies
009 of this software.
010
011 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
012 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
013 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
014 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
015 SUCH DAMAGE.
016
017 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
018 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
019 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
020 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
021 CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
022 ENHANCEMENTS, OR MODIFICATIONS.
023
024 PT_COPYRIGHT_VERSION_2
025 COPYRIGHTENDKEY
026
027 */
028package ptolemy.actor.lib;
029
030import ptolemy.data.BooleanToken;
031import ptolemy.data.DoubleToken;
032import ptolemy.data.expr.Parameter;
033import ptolemy.data.type.BaseType;
034import ptolemy.kernel.CompositeEntity;
035import ptolemy.kernel.util.IllegalActionException;
036import ptolemy.kernel.util.NameDuplicationException;
037
038///////////////////////////////////////////////////////////////////
039//// Bernoulli
040
041/**
042 Produce a random sequence of booleans.  The output is of type BooleanToken.
043 The values that are generated are independent and identically distributed,
044 where the probability of <i>true</i> is given by the parameter
045 <i>trueProbability</i>.
046 The seed can be specified as a parameter to control the sequence that is
047 generated.
048 This actor uses the class java.util.Random to generate random numbers.
049 Note that if the parameters are changed during execution of the
050 model, there is a one iteration delay before the changes take
051 effect.
052
053 @author Edward A. Lee
054 @version $Id$
055 @since Ptolemy II 0.3
056 @Pt.ProposedRating Green (eal)
057 @Pt.AcceptedRating Green (bilung)
058 @see ptolemy.actor.lib.DiscreteRandomSource
059 @see ptolemy.actor.lib.Rician
060 @see ptolemy.actor.lib.Triangular
061 @see ptolemy.actor.lib.Uniform
062 */
063public class Bernoulli extends RandomSource {
064    /** Construct an actor with the given container and name.
065     *  @param container The container.
066     *  @param name The name of this actor.
067     *  @exception IllegalActionException If the actor cannot be contained
068     *   by the proposed container.
069     *  @exception NameDuplicationException If the container already has an
070     *   actor with this name.
071     */
072    public Bernoulli(CompositeEntity container, String name)
073            throws NameDuplicationException, IllegalActionException {
074        super(container, name);
075
076        output.setTypeEquals(BaseType.BOOLEAN);
077
078        trueProbability = new Parameter(this, "trueProbability");
079        trueProbability.setExpression("0.5");
080        trueProbability.setTypeEquals(BaseType.DOUBLE);
081    }
082
083    ///////////////////////////////////////////////////////////////////
084    ////                     ports and parameters                  ////
085
086    /** The probability of <i>true</i>.
087     *  This parameter contains a DoubleToken, initially with value 0.5.
088     */
089    public Parameter trueProbability;
090
091    ///////////////////////////////////////////////////////////////////
092    ////                         public methods                    ////
093
094    /** Send a random boolean to the output.
095     *  This number is only changed in the prefire() method, so it will
096     *  remain constant throughout an iteration.
097     *  @exception IllegalActionException If calling send() or super.fire()
098     *  throws it.
099     */
100    @Override
101    public void fire() throws IllegalActionException {
102        super.fire();
103        output.send(0, new BooleanToken(_current));
104    }
105
106    ///////////////////////////////////////////////////////////////////
107    ////                         protected methods                 ////
108
109    /** Generate a new random number.
110     *  @exception IllegalActionException If parameter values are incorrect.
111     */
112    @Override
113    protected void _generateRandomNumber() throws IllegalActionException {
114        if (_random.nextDouble() < ((DoubleToken) trueProbability.getToken())
115                .doubleValue()) {
116            _current = true;
117        } else {
118            _current = false;
119        }
120    }
121
122    ///////////////////////////////////////////////////////////////////
123    ////                         private variables                 ////
124
125    /** The random boolean for the current iteration. */
126    private boolean _current;
127}