1 /*
2 * Copyright (c) 2001, Zoltan Farkas All Rights Reserved.
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2.1 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 */
18
19 package net.sf.zel.instr;
20
21 import net.sf.zel.nr.Operable;
22 import net.sf.zel.vm.*;
23
24 /**
25 * Add takes two objects from the top of the stack and puts the sum back
26 * @author zoly
27 * @version 1.0
28 */
29 public final class ADD extends Instruction
30 {
31 private static final long serialVersionUID = 6127414006563169983L;
32
33 private ADD(){};
34
35 /**
36 * ADD Instruction microcode
37 * if any of the operands are null the result is null
38 * @param context ExecutionContext
39 * @throws com.zoltran.z.vm.ZExecutionException
40 */
41 public void execute(ExecutionContext context) throws ZExecutionException
42 {
43 final Operable val1 = (Operable) context.popSyncStackVal();
44 final Operable val2 = (Operable) context.popSyncStackVal();
45
46 if (val1 != null && val2 != null)
47 {
48 context.stack.push(val1.add(val2));
49 } else
50 {
51 context.stack.push(null);
52 }
53 context.ip++;
54 }
55 /**
56 * Add instance
57 */
58 public static final Instruction instance = new ADD();
59 }