GUMinus


1   /* @author rich
2    * Created on 05-Mar-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.groupJep.function;
9   import org.nfunk.jep.function.*;
10  import org.lsmp.djep.groupJep.*;
11  import java.util.*;
12  import org.nfunk.jep.*;
13  /**
14   * @author Rich Morris
15   * Created on 05-Mar-2004
16   */
17  public class GUMinus extends PostfixMathCommand {
18      private GroupI group;
19      /**
20       * 
21       */
22      private GUMinus() { }
23      public GUMinus(GroupI group)
24      {
25          numberOfParameters = 1;
26          this.group = group;
27      }
28  
29      /**
30       * Calculates the result of applying the "+" operator to the arguments from
31       * the stack and pushes it back on the stack.
32       */
33      public void run(Stack stack) throws ParseException {
34          checkStack(stack);// check the stack
35          
36          Object   sum = stack.pop();
37          stack.push(uminus(sum));
38          return;
39      }
40  
41      public Object   uminus(Object   param1) throws ParseException {
42          if (param1 instanceof Number  ) {
43                  return group.getInverse((Number  )param1);
44          }
45          throw new ParseException("Invalid parameter type");
46      }
47  }
48

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