XVariable


1   /* @author rich
2    * Created on 28-Feb-2004
3    *
4    * This code is covered by a Creative Commons
5    * Attribution, Non Commercial, Share Alike license
6    * <a HREF="http://creativecommons.org/licenses/by-nc-sa/1.0">License</a>
7    */
8   package org.lsmp.djep.xjep;
9   
10  import org.nfunk.jep.*;
11  
12  /**
13   * Variables which have their equations stored.
14   * 
15   * @author Rich Morris
16   * Created on 28-Feb-2004
17   */
18  public class XVariable extends Variable {
19      private Node equation=null;
20  
21      public XVariable(String   name) {
22          super(name);
23      }
24  
25      public XVariable(String   name, Object   value) {
26          super(name, value);
27      }
28  
29      /** Does this variable has an associated equation? **/
30      public boolean hasEquation() { return equation != null; }
31      /** sets the equation */
32      public void setEquation(Node eqn)
33      {
34          equation = eqn; 
35          this.setValidValue(false);
36      }
37      /** get the equation */
38      public Node getEquation() { return equation; }
39      
40      /**
41       * Calculates the value for the variables equation and returns that value.  
42       * 
43       */
44      public Object   calcValue(XJep jep) throws Exception  
45      {
46          if(equation == null ) return getValue();
47          Object   val = jep.evaluate(equation);
48          setValue(val);
49          return val;
50      }
51  
52      /** Returns a string rep of variable with its equation and value. */ 
53      public String   toString(PrintVisitor pv)
54      {
55          StringBuffer   sb = new StringBuffer  (name);
56          sb.append(": val "+getValue() );
57          if(!hasValidValue()) sb.append("(invalid)");
58          sb.append(" ");
59          if(getEquation()!=null) sb.append(pv.toString(getEquation()));
60          else sb.append("no equation");
61          return sb.toString();
62      }
63  }
64
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