01: package org.ofbiz.rules.parse;
02:
03: import java.util.*;
04:
05: /**
06: * <p><b>Title:</b> Empty
07: * <p><b>Description:</b> None
08: * <p>Copyright (c) 1999 Steven J. Metsker.
09: * <p>Copyright (c) 2001 The Open For Business Project - www.ofbiz.org
10: *
11: * <p>Permission is hereby granted, free of charge, to any person obtaining a
12: * copy of this software and associated documentation files (the "Software"),
13: * to deal in the Software without restriction, including without limitation
14: * the rights to use, copy, modify, merge, publish, distribute, sublicense,
15: * and/or sell copies of the Software, and to permit persons to whom the
16: * Software is furnished to do so, subject to the following conditions:
17: *
18: * <p>The above copyright notice and this permission notice shall be included
19: * in all copies or substantial portions of the Software.
20: *
21: * <p>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
22: * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
23: * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
24: * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
25: * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT
26: * OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
27: * THE USE OR OTHER DEALINGS IN THE SOFTWARE.
28: *
29: * <br>
30: * <p>An <code>Empty</code> parser matches any assembly once,
31: * and applies its assembler that one time.
32: * <p>
33: * Language elements often contain empty parts. For example,
34: * a language may at some point allow a list of parameters
35: * in parentheses, and may allow an empty list. An empty
36: * parser makes it easy to match, within the
37: * parenthesis, either a list of parameters or "empty".
38: *
39: * @author Steven J. Metsker
40: * @version 1.0
41: */
42: public class Empty extends Parser {
43:
44: /**
45: * Accept a "visitor" and a collection of previously visited
46: * parsers.
47: *
48: * @param pv the visitor to accept
49: * @param visited a collection of previously visited parsers
50: */
51: public void accept(ParserVisitor pv, List visited) {
52: pv.visitEmpty(this , visited);
53: }
54:
55: /**
56: * Given a set of assemblies, this method returns the set as
57: * a successful match.
58: *
59: * @return the input set of states
60: * @param in a vector of assemblies to match against
61: */
62: public List match(List in) {
63: return elementClone(in);
64: }
65:
66: /**
67: * There really is no way to expand an empty parser, so
68: * return an empty vector.
69: */
70: protected List randomExpansion(int maxDepth, int depth) {
71: return new ArrayList();
72: }
73:
74: /**
75: * Returns a textual description of this parser.
76: */
77: protected String unvisitedString(List visited) {
78: return " empty ";
79: }
80: }
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