outputarc.java

Rakiura JFern是一个非常轻型的带有模拟器的Petri网络框架

// This is copyrighted source file, part of Rakiura JFern package. 
// See the file LICENSE for copyright information and the terms and conditions
// for copying, distributing and modifications of Rakiura JFern package.
// Copyright (C) 1999-2002 by Mariusz Nowostawski and others  [http://www.rakiura.org]

package org.rakiura.cpn;

/**
 * Represents an output Arc in Petri Net.
 * 
 *<br><br>
 * OutputArc.java<br>
 * Created: Mon Sep 25 11:49:12 2000<br>
 *
 *@author <a href="mailto:[e-mail]">Mariusz Nowostawski</a>
 *@version 2.1.0 $Revision: 1.7 $
 *@since 1.0
 */
public class OutputArc extends AbstractArc {
  
  /**
   * Default expression. */
  private Expression expr = new Expression();


  /**
   * Creates a new <code>OutputArcAdapter</code> instance.
   */
  protected OutputArc() {
  }

  /**
   * Creates a new <code>OutputArcAdapter</code> instance.
   * @param aFrom a <code>Transition</code> value
   * @param aTo a <code>Place</code> value
   */
  public OutputArc(final Transition aFrom, final Place aTo){
    super(aFrom, aTo);
    aFrom.addOutput(this);
    aTo.addOutput(this);
  }
  

  /**
   * Returns a multiset of tokens expressed by the inscription. 
   * In JFern the inscription language is Java.
   * @return a <code>Multiset</code> value
   */
  public Multiset expression() {
    return this.expr.evaluate();
  }

  /**
   * Sets the expression for this arc.
   *@param anExpr an <code>Expression</code> value
   */
  public void setExpression(final Expression anExpr) {
    this.expr = anExpr;
  }

  /**
   * Visitor pattern.
   * @param aVisitor a <code>NetVisitor</code> value
   * @return a <code>NetElement</code> value
   */
  public NetElement apply(final NetVisitor aVisitor) {
    aVisitor.outputArc(this);
    return this;
  }


  /**
   * Represents an expression for the output arc.
   * 
   *<br><br>
   * OutputArcExpression.java<br>
   * Created: Tue Apr 23 23:34:20 2002<br>
   *
   *@author  <a href="[e-mail]">Mariusz</a>
   *@version $Revision: 1.7 $ $Date: 2002/04/26 06:23:18 $
   *@since 2.0
   */
  public class Expression implements Context {

    /**
     * Evaluates this expression.
     * Expression returns single multiset. This method 
     * implements the actual expression on the output arc.
     * This implementation returns an empty multiset, which
     * is equivalent to an empty arc inscription. User
     * needs to overwrite this method to provide some output
     * arc functionality, token generation, and the like.
     *@return a single multiset.
     */
    public Multiset evaluate(){ 
      return new Multiset(); 
    }
    
    
    public void var(final String aVariable) {
      getContext().var(aVariable);
    }
    
    public void var(final int aNumber) {
      getContext().var(aNumber);
    }

    public Object get(final String aVariable) {
      return getContext().get(aVariable);
    }
    
    public Multiset getMultiset() {
      return getContext().getMultiset();
    }
    
  } // OutputArcExpression


} // OutputArc
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