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
20 package net.sf.zel.instr.var;
21
22 import net.sf.zel.instr.*;
23 import net.sf.zel.vm.*;
24 import java.util.*;
25 import net.sf.zel.nr.OperableDouble;
26 import net.sf.zel.nr.OperableNumber;
27
28
29 public final class AVG extends Instruction
30 {
31
32 /**
33 * instance
34 */
35 public static final Instruction instance = new AVG();
36
37 private static final long serialVersionUID = 4115104411671388053L;
38
39 private AVG(){};
40
41 /**
42 * RAVG Instruction microcode
43 * @param context ExecutionContext
44 * @throws ZExecutionException
45 */
46 public void execute(ExecutionContext context) throws ZExecutionException
47 {
48 final MatchIterator iterator = new MatchIterator((String) context.popSyncStackVal());
49 context.stack.pop();
50 Averager stuff = new Averager();
51 iterator.iterate(stuff, context.memContext);
52 context.stack.push(stuff.getAverage());
53 context.ip++;
54 }
55
56 private static final class Averager implements MatchIterator.DoStuff
57 {
58
59 /**
60 * summ variable
61 */
62 private transient double sum = 0;
63 /**
64 * count variable
65 */
66 private transient double cnt = 0;
67
68 public OperableDouble getAverage()
69 {
70 if (cnt == 0)
71 {
72 return null;
73 } else
74 {
75 return new OperableDouble(sum/cnt);
76 }
77 }
78
79 public void execute(Object obj, List context)
80 {
81 if (obj instanceof OperableNumber)
82 {
83 sum += ((Number) obj).doubleValue();
84 cnt++;
85 }
86 }
87 }
88 }