|
1 package ppg.atoms;
2
3 import java.util.*;
4 import ppg.parse.*;
5 import ppg.util.*;
6
7 public class Production implements Unparse
8 {
9 private Nonterminal lhs;
10 private Vector rhs;
11 private static String  HEADER = "ppg [nterm]: ";
12
13 public Production (Nonterminal lhs, Vector rhs) {
14 this.lhs = lhs;
15 this.rhs = rhs;
16 }
17
18 public Nonterminal getLHS() { return lhs; }
19 public void setLHS(Nonterminal nt) { lhs = nt; }
20 public Vector getRHS() { return rhs; }
21
22 public Object clone() {
23 return new Production((Nonterminal) lhs.clone(),
24 (Vector) rhs.clone());
25 }
26
27 public void drop (Production prod) {
28 Vector toDrop = prod.getRHS();
30 Vector target, source;
32 for (int i=0; i < toDrop.size(); i++) {
33 target = (Vector) toDrop.elementAt(i);
34 for (int j=0; j < rhs.size(); j++) {
35 source = (Vector) rhs.elementAt(j);
36 if (isSameProduction(target, source)) {
37 rhs.removeElementAt(j);
38 break;
39 }
40 if (j == rhs.size() - 1) {
42 System.err.println(HEADER+"no match found for production:");
43 System.err.print(prod.getLHS() + " ::= ");
44 for (int k=0; k < target.size(); k++) {
45 System.err.print(target.elementAt(k)+" ");
46 }
47 System.exit(1);
48 }
49 }
50 }
51 }
52
53 public static boolean isSameProduction (Vector u, Vector v) {
54 int uIdx = 0, vIdx = 0;
55 GrammarPart ug = null, vg = null;
56
57 while (uIdx < u.size() && vIdx < v.size()) {
58 ug = (GrammarPart) u.elementAt(uIdx);
59 if (ug instanceof SemanticAction) {
60 uIdx++;
61 continue;
62 }
63
64 vg = (GrammarPart) v.elementAt(vIdx);
65 if (vg instanceof SemanticAction) {
66 vIdx++;
67 continue;
68 }
69
70 if (! ug.equals(vg))
71 return false;
72 else {
73 uIdx++;
74 vIdx++;
75 }
76 }
77
78 if (uIdx == u.size() && vIdx == v.size()) {
79 return true;
81 } else {
82 if (uIdx < u.size()) {
85 for (; uIdx < u.size(); uIdx++) {
86 ug = (GrammarPart) u.elementAt(uIdx);
87 if (! (ug instanceof SemanticAction))
88 return false;
89 }
90 return true;
91 } else { for (; vIdx < v.size(); vIdx++) {
93 vg = (GrammarPart) v.elementAt(vIdx);
94 if (! (vg instanceof SemanticAction))
95 return false;
96 }
97 return true;
98 }
99 }
100 }
101
102 public void union (Production prod) {
103 Vector additional = prod.getRHS();
104 union(additional);
105 }
106
107 public void union (Vector prodList) {
108 Vector toAdd, current;
109 for (int i=0; i < prodList.size(); i++) {
110 toAdd = (Vector) prodList.elementAt(i);
111 for (int j=0; j < rhs.size(); j++) {
112 current = (Vector) rhs.elementAt(i);
113 if (isSameProduction(toAdd, current))
114 break;
115 if (j == rhs.size() - 1)
116 rhs.addElement(toAdd);
117 }
118 }
119 }
120
121 public void add (Production prod) {
122 Vector additional = prod.getRHS();
124 for (int i=0; i < additional.size(); i++) {
125 rhs.addElement( additional.elementAt(i) );
126 }
127 }
128 public void addToRHS (Vector rhsPart) {
129 rhs.addElement(rhsPart);
130 }
131
132 private void assertSameLHS(Production prod, String function) {
133 if (! (prod.getLHS().equals(lhs)) ) {
134 System.err.println(HEADER + "nonterminals do not match in Production."+
135 function + "(): current is "+lhs+", given: "+
136 prod.getLHS());
137 System.exit(1);
138 }
139 }
140 public void unparse (CodeWriter cw) {
141 cw.begin(0);
142 cw.write(lhs.toString() + " ::=");
143 cw.allowBreak(3);
144 Vector rhs_part;
145 for (int i=0; i < rhs.size(); i++) {
146 rhs_part = (Vector) rhs.elementAt(i);
147 for (int j=0; j < rhs_part.size(); j++) {
148 cw.write(" ");
149 ((GrammarPart) rhs_part.elementAt(j)).unparse(cw);
150 }
151 if (i < rhs.size() - 1) {
152 cw.allowBreak(0);
153 cw.write(" | ");
154 }
155 }
156 cw.write(";");
157 cw.newline(); cw.newline();
158
159 cw.end();
160 }
161
162 public String toString() {
163 String result = lhs.toString();
164 Vector rhs_part;
165 result += " ::=";
166 for (int i=0; i < rhs.size(); i++) {
167 rhs_part = (Vector) rhs.elementAt(i);
168 for (int j=0; j < rhs_part.size(); j++) {
169 result += " " + rhs_part.elementAt(j).toString();
170 }
171 if (i < rhs.size() - 1)
172 result += " | ";
173 }
174 return result + ";";
175 }
176 }
177 |
Popular Tags |
Java API By Example, From Geeks To Geeks.