001: package org.ofbiz.rules.engine;
002:
003: import java.util.*;
004:
005: /**
006: * <p><b>Title:</b> Unification
007: * <p><b>Description:</b> None
008: * <p>Copyright (c) 1999 Steven J. Metsker.
009: * <p>Copyright (c) 2001 The Open For Business Project - www.ofbiz.org
010: *
011: * <p>Permission is hereby granted, free of charge, to any person obtaining a
012: * copy of this software and associated documentation files (the "Software"),
013: * to deal in the Software without restriction, including without limitation
014: * the rights to use, copy, modify, merge, publish, distribute, sublicense,
015: * and/or sell copies of the Software, and to permit persons to whom the
016: * Software is furnished to do so, subject to the following conditions:
017: *
018: * <p>The above copyright notice and this permission notice shall be included
019: * in all copies or substantial portions of the Software.
020: *
021: * <p>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
022: * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
023: * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
024: * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
025: * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT
026: * OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
027: * THE USE OR OTHER DEALINGS IN THE SOFTWARE.
028: *
029: * <br>
030: * <p>A Unification is a collection of variables.
031: *
032: * Structures and variables use unifications to keep track of the
033: * variable assignments that make a proof work. The unification
034: * class itself provides behavior for adding and accessing
035: * variables.
036: *
037: * @author Steven J. Metsker
038: * @version 1.0
039: */
040:
041: public class Unification {
042: public static final Unification empty = new Unification();
043: List vector;
044:
045: /**
046: * Creates an empty unification.
047: */
048: public Unification() {
049: }
050:
051: /**
052: * Creates a unification that starts off including a single
053: * variable.
054: *
055: * @param Variable the variable with which the unification
056: * begins
057: */
058: public Unification(Variable v) {
059: addVariable(v);
060: }
061:
062: /**
063: * Adds a variable to this unification.
064: *
065: * @param Variable the variable to add to this unification
066: *
067: * @return this unification
068: */
069: public Unification addVariable(Variable v) {
070: if (!vector().contains(v)) {
071: vector.add(v);
072: }
073: return this ;
074: }
075:
076: /**
077: * Adds all the variables of another unification to this one.
078: *
079: * @param Unification the unification to append
080: *
081: * @return this unification
082: */
083: public Unification append(Unification u) {
084: for (int i = 0; i < u.size(); i++) {
085: addVariable(u.variableAt(i));
086: }
087: return this ;
088: }
089:
090: /**
091: * Return the variables in this unification.
092: *
093: * @return the variables in this unification.
094: */
095: public Enumeration elements() {
096: return Collections.enumeration(vector());
097: }
098:
099: /**
100: * Returns the number of variables in this unification.
101: *
102: * @return int the number of variables in this unification
103: */
104: public int size() {
105: if (vector == null) {
106: return 0;
107: }
108: return vector.size();
109: }
110:
111: /**
112: * Returns a string representation of this unification.
113: *
114: * @return a string representation of this unification
115: */
116: public String toString() {
117: StringBuffer buf = new StringBuffer();
118:
119: for (int i = 0; i < size(); i++) {
120: if (i > 0) {
121: buf.append(", ");
122: }
123: buf.append(variableAt(i).definitionString());
124: }
125: return buf.toString();
126: }
127:
128: /**
129: * Returns a string representation of this unification,
130: * without printing variable names.
131: *
132: * @return a string representation of this unification,
133: * without printing variable names
134: */
135: public String toStringQuiet() {
136: StringBuffer buf = new StringBuffer();
137:
138: for (int i = 0; i < size(); i++) {
139: if (i > 0) {
140: buf.append(", ");
141: }
142: buf.append(variableAt(i));
143: }
144: return buf.toString();
145: }
146:
147: /**
148: * Asks all the contained variables to unbind.
149: */
150: public void unbind() {
151: for (int i = 0; i < size(); i++) {
152: variableAt(i).unbind();
153: }
154: }
155:
156: /**
157: * Returns the variable at the indicated index.
158: *
159: * @param int the index of the variable to return
160: *
161: * @return variable the variable at the indicated index
162: */
163: protected Variable variableAt(int i) {
164: return (Variable) vector().get(i);
165: }
166:
167: /**
168: * lazy-initialize this unification's vector
169: */
170: protected List vector() {
171: if (vector == null) {
172: vector = new ArrayList();
173: }
174: return vector;
175: }
176: }
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