|
1
3 package ro.infoiasi.donald.compiler.parser;
4
5 import ro.infoiasi.donald.compiler.cfg.*;
6
7 public class LR0Item
8 implements Cloneable  {
9 private Production p;
10 private WordIterator it;
11
12 public LR0Item(Production p, int position) {
13 this.p = p;
14 Word w = p.getRHS();
15 if (position >=0 && position<=w.size()) {
16 it = w.iterator();
17 while (position>0) {
18 it.next();
19 position--;
20 }
21 } else {
22 throw new IndexOutOfBoundsException ();
23 }
24 }
25
26 public LR0Item(Production p) {
27 this(p, 0);
28 }
29
30 public boolean equals(Object o) {
31 return (o instanceof LR0Item &&
32 p.equals(((LR0Item)o).p) &&
33 getPosition() == ((LR0Item)o).getPosition());
34 }
35
36 public int hashCode() {
37 return 17+p.hashCode()*37+getPosition();
38 }
39
40 public Object clone() {
41 try {
42 LR0Item item = (LR0Item)super.clone();
43 item.it = (WordIterator)it.clone();
44 return item;
45 } catch (CloneNotSupportedException e) {
46 throw new RuntimeException (e);
47 }
48 }
49
50 public LR0Item nextItem() {
51 LR0Item item = (LR0Item)clone();
52 item.it.next();
53 return item;
54 }
55
56 public boolean isComplete() {
57 return !it.hasNext();
58 }
59
60 public boolean isNew() {
61 return !it.hasPrev();
62 }
63
64 public Symbol getNextSymbol() {
65 return it.getNext();
66 }
67
68 public Production getProduction() {
69 return p;
70 }
71
72 public int getPosition() {
73 return it.nextIndex();
74 }
75
76 public String toString() {
77 return p.getLHS()+" ::= "+it.prefix()+" * "+it.suffix();
78 }
79
80 Word suffix() {
81 return it.suffix();
82 }
83
84 public static void main(String args[]) {
85 Terminals t = new Terminals();
86 Terminal a = t.addNew("a");
87 Terminal b = t.addNew("b");
88 Terminal c = t.addNew("c");
89 NonTerminals v = new NonTerminals();
90 NonTerminal S = v.addNew("S");
91 NonTerminal A = v.addNew("A");
92 NonTerminal B = v.addNew("B");
93 Word w = new Word();
94 w.addLast(a); w.addLast(A); w.addLast(b); w.addLast(B); w.addLast(c);
95 Productions p = new Productions();
96 Production prod = p.addNew(S, w);
97 LR0Item items[] = new LR0Item[w.size()+1];
98 items[0] = new LR0Item(prod);
99 System.out.println("items[0]: "+items[0]);
100 for (int i = 1; i<=w.size(); i++) {
101 items[i] = items[i-1].nextItem();
102 System.out.println("items["+i+"]: "+items[i]);
103 }
104 for (int i = 0; i<=w.size(); i++) {
106 System.out.println("items["+i+"]: "+items[i]);
107 }
108 }
109 }
110 |
Popular Tags |
Java API By Example, From Geeks To Geeks.