1 // Copyright 2006 all rights reserved; see LICENSE file for BSD-style license
3 package edu.berkeley.sbp;
4 import edu.berkeley.sbp.util.*;
5 import edu.berkeley.sbp.*;
6 import edu.berkeley.sbp.*;
9 import java.lang.reflect.*;
10 import java.lang.ref.*;
12 /** <font color=green>juxtaposition; zero or more adjacent Elements; can specify a rewriting</font> */
13 public abstract class Sequence implements Iterable<Element>, SequenceOrElement {
15 protected final Element[] elements;
17 boolean needed_or_hated = false;
18 boolean in_a_union = false;
20 final HashSet<Sequence> needs = new HashSet<Sequence>();
21 final HashSet<Sequence> hates = new HashSet<Sequence>();
23 // FIXME: these are ugly -- migrate into Grammar
24 HashMap<Sequence,Boolean> canNeed = new HashMap<Sequence,Boolean>();
25 HashMap<Sequence,Boolean> canKill = new HashMap<Sequence,Boolean>();
27 final Position firstp;
31 // Static Constructors //////////////////////////////////////////////////////////////////////////////
33 /** create a sequence of one element */
34 public static Sequence create(Element e) { return create(new Element[] { e }, 0); }
36 /** create a sequence which drops the result of all but one of its element */
37 public static Sequence create(Element[] e, int which) {
38 return new Singleton(e, which); }
40 /** create a sequence which always evaluates to a constant result */
41 public static Sequence create(Object result, Element[] e) {
42 return new RewritingSequence(result, e, trues(e.length)); }
44 private static boolean[] trues(int length) {
45 boolean[] ret = new boolean[length];
46 for(int i=0; i<ret.length; i++) ret[i] = true;
51 * create a sequence (general form)
52 * @param head the head of the output tree
53 * @param e the elements to match
54 * @param drop only elements of <tt>e</tt> whose corresponding <tt>boolean</tt> in <tt>drops</tt>
55 * is <i>false</i> will be included in the output tree
56 * @param lifts which (if any) child trees to lift
58 public static Sequence create(Object head, Element[] e, boolean[] drop) {
59 return create(head, e, drop, new boolean[e.length]); }
60 public static Sequence create(Object head, Element[] e, boolean[] drop, boolean[] lifts) {
61 if (lifts==null) lifts = new boolean[e.length];
62 return new RewritingSequence(head, e, drop, lifts);
65 /** return a new sequence identical to this one, but with a positive conjunct <tt>s</tt> */
66 public Sequence and(Sequence s) {
68 throw new RuntimeException("you may not use a sequence as a conjunct if it belongs to a Union");
71 s.needed_or_hated=true;
75 /** return a new sequence identical to this one, but with a negative conjunct <tt>s</tt> */
76 public Sequence andnot(Sequence s) {
78 throw new RuntimeException("you may not use a sequence as a conjunct if it belongs to a Union");
81 s.needed_or_hated=true;
85 /** return a new sequence identical to this one, but with a follow-set restricted to <tt>a</tt> */
86 public Sequence followedBy(Atom a) { Sequence ret = dup(); ret.follow = a; return ret; }
88 ////////////////////////////////////////////////////////////////////////////////
90 abstract Sequence _clone();
91 private Sequence dup() {
92 Sequence ret = _clone();
93 for(Sequence s : needs) { ret.needs.add(s); }
94 for(Sequence s : hates) { ret.hates.add(s); }
99 Iterable<Sequence> needs() { return needs; }
100 Iterable<Sequence> hates() { return hates; }
102 Position firstp() { return firstp; }
103 Position lastp() { return firstp().last(); }
105 public Iterator<Element> iterator() { return new ArrayIterator<Element>(elements); }
106 protected Sequence(Element[] elements) {
107 this.elements = elements;
108 for(int i=0; i<elements.length; i++)
109 if (elements[i]==null)
110 throw new RuntimeException("cannot have nulls in a sequence: " + this);
111 this.firstp = new Position(0, null);
114 abstract Forest epsilonForm(Input.Region loc, Grammar cache);
116 protected abstract <T> Forest<T> postReduce(Input.Region loc, Forest<T>[] args, Position p);
119 // Position //////////////////////////////////////////////////////////////////////////////
121 /** the imaginary position before or after an element of a sequence; corresponds to an "LR item" */
122 class Position implements IntegerMappable {
126 private Forest zero = null;
128 public Forest zero(Input.Region reg) {
129 if (zero != null) return zero;
130 if (pos > 0) throw new RuntimeException("Position.zero(): pos>0");
131 return zero = rewrite(reg);
135 private final Position next;
136 private final Position prev;
137 final Forest[] holder;
139 private Position(int pos, Position prev) {
141 this.next = pos==elements.length ? null : new Position(pos+1, this);
142 this.holder = new Forest[elements.length];
146 boolean isFirst() { return pos==0; }
148 /** the element immediately after this Position, or null if this is the last Position */
149 public Element element() { return pos>=elements.length ? null : elements[pos]; }
151 /** the element which produces the sequence to which this Position belongs */
152 public Sequence owner() { return Sequence.this; }
154 /** the next Position (the Position after <tt>this.element()</tt>) */
155 public Position next() { return next; }
157 /** true iff this Position is the last one in the sequence */
158 public boolean isLast() { return next()==null; }
159 public Position last() { return isLast() ? this : next().last(); }
160 public Position prev() { return prev; }
162 // Position /////////////////////////////////////////////////////////////////////////////////
164 final <T> Forest<T> rewrite(Input.Region loc, Grammar cache) {
165 if (this==firstp()) epsilonForm(loc, cache);
166 for(int i=0; i<pos; i++) if (holder[i]==null) throw new Error("realbad " + i);
167 for(int i=pos; i<elements.length; i++) {
168 if (holder[i]==null) holder[i] = ((Union)elements[i]).epsilonForm(loc, cache);
169 if (holder[i]==null) throw new Error("bad");
171 return Sequence.this.postReduce(loc, holder, this);
174 public String toString() {
175 StringBuffer ret = new StringBuffer();
177 for(Position p = Sequence.this.firstp(); p != null; p = p.next()) {
179 if (p==this) ret.append(" | ");
180 if (p.element()!=null) ret.append(p.element());
181 else ret.append(' ');
184 return ret.toString();
186 private final int idx = master_position_idx++;
187 public int toInt() { return idx; }
189 private static int master_position_idx = 0;
191 // toString //////////////////////////////////////////////////////////////////////////////
193 public String toString() { return toString(new StringBuffer(), false).toString(); }
194 StringBuffer toString(StringBuffer sb) { return toString(sb, true); }
195 StringBuffer toString(StringBuffer sb, boolean spacing) {
196 for(int i=0; i<elements.length; i++) {
197 sb.append(elements[i]+"");
200 if (follow != null) {
204 for(Sequence s : needs) {
208 for(Sequence s : hates) {
216 // Specialized Subclasses //////////////////////////////////////////////////////////////////////////////
218 static class Constant extends Sequence {
219 private final Object result;
220 public Constant(Element[] e, Object result) {
222 if (result==null) throw new Error("constant sequences may not have result==null");
223 this.result = result;
225 Sequence _clone() { return new Constant(elements, result); }
226 public <T> Forest<T> postReduce(Input.Region loc, Forest<T>[] args, Position p) {
227 return (Forest<T>)Forest.create(loc, result, null, false);
229 Forest epsilonForm(Input.Region loc, Grammar cache) {
230 return Forest.create(loc, result, null, false);
234 static class Singleton extends Sequence {
235 private final int idx;
236 public Singleton(Element e) { this(new Element[] { e }, 0); }
237 public Singleton(Element[] e, int idx) { super(e); this.idx = idx; }
238 public <T> Forest<T> postReduce(Input.Region loc, Forest<T>[] args, Position p) { return args[idx]; }
239 Sequence _clone() { return new Singleton(elements,idx); }
240 Forest epsilonForm(Input.Region loc, Grammar cache) {
241 return ((Union)elements[idx]).epsilonForm(loc, cache);
245 static class RewritingSequence extends Sequence {
247 private final boolean[] drops;
248 private final boolean[] lifts;
249 Sequence _clone() { return new RewritingSequence(tag, elements, drops); }
250 public RewritingSequence(Object tag, Element[] e) { this(tag, e, null); }
251 public RewritingSequence(Object tag, Element[] e, boolean[] drops) { this(tag, e, drops, new boolean[e.length]); }
252 public RewritingSequence(Object tag, Element[] e, boolean[] drops, boolean[] lifts) {
254 if (tag==null) throw new Error();
256 this.drops = drops == null ? new boolean[e.length] : drops;
258 for(int i=0; i<this.drops.length; i++) if (!this.drops[i]) count++;
259 this.lifts = new boolean[count];
261 for(int i=0; i<this.drops.length; i++)
263 this.lifts[j++] = lifts[i];
265 public <T> Forest<T> postReduce(Input.Region loc, Forest<T>[] args, Position p) {
266 Forest<T>[] args2 = new Forest[lifts.length];
268 for(int i=0; i<args.length; i++) if (!drops[i]) args2[j++] = args[i];
269 return Forest.create(loc, (T)tag, args2, lifts);
271 public StringBuffer toString(StringBuffer sb, boolean spacing) {
272 int len = sb.length();
274 sb.append("\""+StringUtil.escapify(tag.toString(),"\"\r\n")+"\":: ");
275 super.toString(sb, spacing);
276 len = sb.length()-len;
277 if (spacing) for(int i=0; i<50-len; i++) sb.append(' ');
280 Forest epsilonForm(Input.Region loc, Grammar cache) {
281 return Forest.create(loc, tag, new Forest[0], lifts);