1 package edu.berkeley.sbp;
2 import edu.berkeley.sbp.util.*;
3 import edu.berkeley.sbp.*;
4 import edu.berkeley.sbp.*;
7 import java.lang.reflect.*;
8 import java.lang.ref.*;
10 /** juxtaposition; zero or more adjacent Elements; can specify a rewriting */
11 public abstract class Sequence extends Element implements Iterable<Element> {
13 // Static Constructors //////////////////////////////////////////////////////////////////////////////
15 /** the empty sequence (matches the empty string) */
16 public static final Sequence empty = new Sequence.Constant.Empty();
18 /** after matching the sequence, do not add anything to the output tree */
19 public static Sequence drop(Element[] e, HashSet<Sequence> and, HashSet<Sequence> not, boolean lame) { return new Constant.Drop(e, and, not, lame); }
21 /** after matching the sequence, insert a constant into the output tree */
22 public static Sequence constant(Element[] e, Object o, HashSet<Sequence> and, HashSet<Sequence> not) { return new Constant(e, o, and, not); }
24 /** after matching the sequence, place the result of the <tt>idx</tt>th match in the output tree */
25 public static Sequence singleton(Element[] e, int idx, HashSet<Sequence> and, HashSet<Sequence> not) { return new Singleton(e, idx, and, not); }
28 * after matching the sequence, create the specified output tree
29 * @param tag the tag for the output tree
30 * @param e the elements to match
31 * @param drops only elements of <tt>e</tt> whose corresponding <tt>boolean</tt> in <tt>drops</tt> is <i>false</i> will be included in the output tree
33 public static Sequence rewritingSequence(Object tag, Element[] e, boolean[] drops, HashSet<Sequence> and, HashSet<Sequence> not) {
34 return new RewritingSequence(tag, e, drops, and, not); }
36 ////////////////////////////////////////////////////////////////////////////////
38 public Element noFollow = null;
39 public final Topology noFollow() { return noFollow==null ? null : noFollow.toAtom(); }
42 if (elements.length!=1) throw new RuntimeException("cannot invoke toAtom() on a Sequence with " + elements.length + " elements: " + this);
43 return elements[0].toAtom();
46 protected final Element[] elements;
48 final HashSet<Sequence> needs;
49 final HashSet<Sequence> hates;
52 final Position firstp;
53 Position firstp() { return firstp; }
55 public Iterator<Element> iterator() { return new ArrayIterator<Element>(elements); }
56 protected Sequence(Element[] elements, HashSet<Sequence> and, HashSet<Sequence> not) {
57 this.needs = and==null ? new HashSet<Sequence>() : and;
58 this.hates = not==null ? new HashSet<Sequence>() : not;
59 this.elements = elements;
60 this.firstp = new Position(0);
63 // DO NOT MESS WITH THE FOLLOWING LINE!!!
64 private Forest.Ref epsilonForm = null;
65 private boolean eps = false;
66 Forest epsilonForm() {
67 if (epsilonForm==null) {
68 epsilonForm = new Forest.Ref();
69 Forest fo = firstp().rewrite(null);
70 epsilonForm.merge(fo);
75 protected abstract <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args);
78 // Position //////////////////////////////////////////////////////////////////////////////
80 /** the imaginary position before or after an element of a sequence; corresponds to an "LR item" */
81 public class Position {
84 private final Position next;
85 final Forest[] holder;
87 private Position(int pos) {
89 this.next = pos==elements.length ? null : new Position(pos+1);
90 this.holder = new Forest[elements.length];
93 boolean isFirst() { return pos==0; }
94 boolean isRightNullable(Walk.Cache cache) {
95 if (isLast()) return true;
96 if (!element().possiblyEpsilon(cache)) return false;
97 return next().isRightNullable(cache);
100 /** the element immediately after this Position, or null if this is the last Position */
101 public Element element() { return pos>=elements.length ? null : elements[pos]; }
103 /** the element which produces the sequence to which this Position belongs */
104 public Sequence owner() { return Sequence.this; }
106 /** the next Position (the Position after <tt>this.element()</tt>) */
107 public Position next() { return next; }
109 /** true iff this Position is the last one in the sequence */
110 public boolean isLast() { return next()==null; }
112 // Reduction /////////////////////////////////////////////////////////////////////////////////
114 final <T> Forest<T> rewrite(Token.Location loc) {
115 if (this==firstp() && eps) return epsilonForm;
117 for(int i=pos; i<elements.length; i++) if (holder[i]==null) holder[i] = elements[i].epsilonForm();
118 Forest<T> ret = Sequence.this.postReduce(loc, holder);
119 for(int k=0; k<pos; k++) holder[k] = null; // to help GC
120 if (this==firstp()) { if (epsilonForm==null) epsilonForm=new Forest.Ref(); epsilonForm.merge(ret); return epsilonForm; }
124 public String toString() {
125 StringBuffer ret = new StringBuffer();
127 for(Position p = Sequence.this.firstp(); p != null; p = p.next()) {
129 if (p==this) ret.append(" | ");
130 if (p.element()!=null) ret.append(p.element().possiblyEpsilon(null) ? "["+p.element()+"]" : p.element());
131 else ret.append(' ');
134 return ret.toString();
139 // toString //////////////////////////////////////////////////////////////////////////////
141 public String toString() { return toString(new StringBuffer(), false).toString(); }
142 StringBuffer toString(StringBuffer sb) { return toString(sb, true); }
143 StringBuffer toString(StringBuffer sb, boolean spacing) {
144 for(int i=0; i<elements.length; i++) {
145 sb.append(elements[i].toString());
152 // Specialized Subclasses //////////////////////////////////////////////////////////////////////////////
154 static class Constant extends Sequence {
155 private final Object result;
156 public Constant(Element[] e, Object result, HashSet<Sequence> and, HashSet<Sequence> not) { super(e, and, not); this.result = result; }
157 public <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args) {
158 return (Forest<T>)Forest.leaf(loc, result, this);
160 static class Drop extends Constant {
161 public Drop(Element[] e, HashSet<Sequence> and, HashSet<Sequence> not, boolean lame) {
162 super(e, null, and, not);
166 static class Empty extends Sequence.Constant.Drop { public Empty() { super(new Element[] { }, null, null, false); } }
169 static class Singleton extends Sequence {
170 private final int idx;
171 public Singleton(Element e, HashSet<Sequence> and, HashSet<Sequence> not) { this(new Element[] { e }, 0, and, not); }
172 public Singleton(Element[] e, int idx, HashSet<Sequence> and, HashSet<Sequence> not) { super(e, and, not); this.idx = idx; }
173 public <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args) { return (Forest<T>)Forest.singleton(loc, args[idx], this); }
176 static class Unwrap extends Sequence {
177 private boolean[] drops;
178 public Unwrap(Element[] e, HashSet<Sequence> and, HashSet<Sequence> not) { super(e, and, not); this.drops = null; }
179 public Unwrap(Element[] e, boolean[] drops, HashSet<Sequence> and, HashSet<Sequence> not) { super(e, and, not); this.drops = drops; }
180 public <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args) {
181 if (drops==null) return Forest.create(loc, null, args, this, true, false);
183 for(int i=0; i<drops.length; i++) if (!drops[i]) count++;
184 Forest<T>[] args2 = new Forest[count];
186 for(int i=0; i<args.length; i++) if (!drops[i]) args2[j++] = args[i];
187 return Forest.create(loc, null, args2, this, true, false);
191 static class RewritingSequence extends Sequence {
192 private final Object tag;
193 private final boolean[] drops;
194 private int count = 0;
195 public RewritingSequence(Object tag, Element[] e, HashSet<Sequence> and, HashSet<Sequence> not) { this(tag, e, null, and, not); }
196 public RewritingSequence(Object tag, Element[] e, boolean[] drops, HashSet<Sequence> and, HashSet<Sequence> not) {
199 this.drops = drops == null ? new boolean[e.length] : drops;
200 for(int i=0; i<this.drops.length; i++) if (!this.drops[i]) count++;
202 public <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args) {
203 Forest<T>[] args2 = new Forest[count];
205 for(int i=0; i<args.length; i++) if (!drops[i]) args2[j++] = args[i];
206 //System.out.println("reduce \""+tag+"\"");
207 return Forest.create(loc, (T)tag, args2, this, false, false);
209 public StringBuffer toString(StringBuffer sb, boolean spacing) {
210 int len = sb.length();
211 super.toString(sb, spacing);
212 len = sb.length()-len;
213 if (spacing) for(int i=0; i<50-len; i++) sb.append(' ');