GMultiply


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 org.lsmp.djep.groupJep.interfaces.*;
12  
13  import java.util.*;
14  import org.nfunk.jep.*;
15  /**
16   * @author Rich Morris
17   * Created on 05-Mar-2004
18   */
19  public class GMultiply extends PostfixMathCommand {
20      private RingI group = null;
21      /**
22       * 
23       */
24      private GMultiply() {   }
25      public GMultiply(GroupI group)
26      {
27          numberOfParameters = -1;
28          if(group instanceof RingI)
29          this.group = (RingI) group;
30      }
31  
32      /**
33       * Calculates the result of applying the "*" operator to the arguments from
34       * the stack and pushes it back on the stack.
35       */
36      public void run(Stack stack) throws ParseException {
37          if(group==null) throw new ParseException("Multiply not implemented for this group.");
38          checkStack(stack);// check the stack
39          
40          Object   sum = stack.pop();
41          Object   param;
42          int i = 1;
43          
44          // repeat summation for each one of the current parameters
45          while (i < curNumberOfParameters) {
46              // get the parameter from the stack
47              param = stack.pop();
48              // add it to the sum (order is important for String arguments)
49              sum = mul(param, sum);
50              i++;
51          }
52          stack.push(sum);
53          return;
54      }
55  
56      public Object   mul(Object   param1, Object   param2) throws ParseException {
57          if (param1 instanceof Number  ) {
58              if (param2 instanceof Number  ) {
59                  return group.mul((Number  )param1, (Number  )param2);
60              }
61          }
62          
63          throw new ParseException("Invalid parameter type");
64      }
65  }
66
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