01 /* This file is part of the project "Hilbert II" - http://www.qedeq.org
02 *
03 * Copyright 2000-2013, Michael Meyling <mime@qedeq.org>.
04 *
05 * "Hilbert II" is free software; you can redistribute
06 * it and/or modify it under the terms of the GNU General Public
07 * License as published by the Free Software Foundation; either
08 * version 2 of the License, or (at your option) any later version.
09 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 */
15
16 package org.qedeq.kernel.bo.logic.wf;
17
18 import org.qedeq.kernel.bo.logic.common.ExistenceChecker;
19 import org.qedeq.kernel.bo.logic.common.FunctionKey;
20 import org.qedeq.kernel.bo.logic.common.PredicateKey;
21 import org.qedeq.kernel.se.common.RuleKey;
22
23
24 /**
25 * This implementation gives always the answer <code>true</code> to the question
26 * <em>exists this predicate?</em>.
27 *
28 * @author Michael Meyling
29 */
30 public final class EverythingExists implements ExistenceChecker {
31
32 /** One and only instance. */
33 private static final ExistenceChecker ALWAYS = new EverythingExists();
34
35 /**
36 * Hidden constructor.
37 */
38 private EverythingExists() {
39 // nothing to do
40 }
41
42 public boolean predicateExists(final String name, final int arguments) {
43 return true;
44 }
45
46 public boolean predicateExists(final PredicateKey predicate) {
47 return true;
48 }
49
50 public boolean isInitialPredicate(final PredicateKey predicate) {
51 return true;
52 }
53
54 public boolean functionExists(final String name, final int arguments) {
55 return true;
56 }
57
58 public boolean functionExists(final FunctionKey function) {
59 return true;
60 }
61
62 public boolean isInitialFunction(final FunctionKey predicate) {
63 return true;
64 }
65
66 public boolean classOperatorExists() {
67 return true;
68 }
69
70 public boolean identityOperatorExists() {
71 return true;
72 }
73
74 public String getIdentityOperator() {
75 return NAME_EQUAL;
76 }
77
78 /**
79 * Get one instance of this class.
80 *
81 * @return Class instance.
82 */
83 public static final ExistenceChecker getInstance() {
84 return ALWAYS;
85 }
86
87 public boolean ruleExists(final RuleKey ruleKey) {
88 return true;
89 }
90
91 }
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