X-Git-Url: http://git.megacz.com/?p=sbp.git;a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FUnion.java;h=8f3ea2e428b6cbc8f1cc3da0d9cc6b7b7b6bb14c;hp=db0db7dca1a322625895ee88f6d338a7934623ba;hb=HEAD;hpb=0516ea34996c86664928ef948013b749876b87ec
diff --git a/src/edu/berkeley/sbp/Union.java b/src/edu/berkeley/sbp/Union.java
index db0db7d..8f3ea2e 100644
--- a/src/edu/berkeley/sbp/Union.java
+++ b/src/edu/berkeley/sbp/Union.java
@@ -1,3 +1,5 @@
+// Copyright 2006-2007 all rights reserved; see LICENSE file for BSD-style license
+
package edu.berkeley.sbp;
import edu.berkeley.sbp.util.*;
import edu.berkeley.sbp.*;
@@ -7,98 +9,123 @@ import java.util.*;
import java.lang.reflect.*;
import java.lang.ref.*;
-/** an element which can produce one of several alternatives */
+/**
+ * an element which can produce one of several alternatives.
+ *
+ *
+ * Unlike the other Elements, Union is not immutable once
+ * constructed. To simulate this desirable feature, it is immutable
+ * once examined by taking its iterator or calling contains().
+ */
public class Union extends Element implements Iterable {
- final String shortForm;
- final boolean synthetic;
- private final List alternatives = new ArrayList();
-
- public Iterator iterator() { return alternatives.iterator(); }
-
- void reachable(HashSet h) { for(Sequence s : alternatives) s.reachable(h); }
+ private final String name;
+ private final boolean synthetic;
+ private boolean viewed = false;
- Topology toAtom() {
- if (alternatives.size()==0) throw new RuntimeException("cannot build an Atom from a Union with no productions");
- Topology ret = null;
- for(Sequence s : this) {
- Topology a = s.toAtom();
- if (ret==null) ret = a.dup();
- else ret = ret.union(a.dup());
- }
- if (ret==null) throw new RuntimeException("confusion on " + this);
- return ret;
- }
+ private final List alternatives = new ArrayList();
- /** adds an alternative */
- public void add(Sequence s) { alternatives.add(s); }
+ public Union(String name) { this(name, false); }
+ public Union(String name, Sequence s) { this(name, s, false); }
+ public Union(String name, Sequence s, boolean synthetic) { this(name, synthetic); add(s); }
/**
* Since every cycle in a non-degenerate grammar contains at
* least one Union, every instance of this class must be able to
* display itself in both "long form" (list of the long forms of
- * its alternatives) and "short form" (some abbreviation).
+ * its alternatives) and "short form" (some name).
*
- * @param shortForm the "short form" display; usually
+ * @param shortForm the "short form" display; for display purposes only
* @param synthetic if true, this Union's "long form" is "obvious" and should not be displayed when printing the grammar
*/
- public Union(String shortForm) { this(shortForm, false); }
- public Union(String shortForm, boolean synthetic) {
- this.shortForm = shortForm;
+ public Union(String name, boolean synthetic) {
+ this.name = name;
this.synthetic = synthetic;
}
- public static Union epsilon = new Union("()");
- static { epsilon.add(Sequence.empty); }
+ public boolean contains(Sequence s) {
+ viewed = true;
+ return alternatives.contains(s);
+ }
+
+ /** iterator over this Union's Sequences */
+ public Iterator iterator() {
+ viewed = true;
+ return alternatives.iterator();
+ }
+
+ /** adds an alternative */
+ public Union add(Sequence s) {
+ if (viewed)
+ throw new RuntimeException("once Union.contains() or Union.iterator() has been invoked, "+
+ "you may not add any more Sequences to it\n "+
+ " union in question: " + this);
+ if (s.needed_or_hated)
+ throw new RuntimeException("you may not add a conjunct directly to a Union");
+ s.in_a_union = true;
+ if (alternatives.contains(s)) return this;
+ alternatives.add(s);
+ return this;
+ }
+
+ /** adds a one-element sequence */
+ public void add(Element e) {
+ add(Sequence.create(e));
+ }
- private Forest.Ref epsilonForm = null;
- Forest epsilonForm() {
- if (epsilonForm != null) return epsilonForm;
- epsilonForm = new Forest.Ref();
+ /** the Forest which results from matching this Union against the empty string at region region */
+ Forest epsilonForm(Input.Region region) {
+ viewed = true;
+ Forest.Many epsilonForm = new Forest.Many();
for(Sequence s : this)
- if (s.possiblyEpsilon(null))
- epsilonForm.merge(s.epsilonForm());
+ if (Element.possiblyEpsilon(s))
+ epsilonForm.merge(s.epsilonForm(region));
return epsilonForm;
}
+
// Display //////////////////////////////////////////////////////////////////////////////
- public String toString() { return shortForm; }
- private static String pad(int i,String s) { return s.length() >= i ? s : pad(i-1,s)+" "; }
- public void toString(StringBuffer sb) {
- if (synthetic) return;
+ boolean isSynthetic() { return synthetic; }
+ String getName() { return name==null ? "(anon_union)" : name; }
+
+ public String toString() {
+ // technically this should be turned on, but we don't make a big deal
+ //viewed = true;
+ if (name != null) return name;
+ StringBuffer sb = new StringBuffer();
+ sb.append("(");
+ bodyToString(sb, "", " | ");
+ sb.append(")");
+ return sb.toString();
+ }
+
+ /** display this union in long/expanded form */
+ public StringBuffer toString(StringBuffer sb) {
+ // technically this should be turned on, but we don't make a big deal
+ //viewed = true;
+ if (synthetic) return sb;
boolean first = true;
+ String before = StringUtil.pad(15, getName()) + " = ";
if (alternatives.size()==0) {
- sb.append(pad(15, shortForm) + "::= ");
- } else for(Sequence s : this) {
- sb.append(pad(15, first ? shortForm : "") + (first ? "::= " : " | "));
- first = false;
- sb.append(s.toString());
+ sb.append(before);
+ } else {
+ bodyToString(sb,
+ before,
+ "\n" + StringUtil.pad(15, "") + " | ");
sb.append('\n');
}
- sb.append('\n');
+ return sb;
}
-
- // SubUnion //////////////////////////////////////////////////////////////////////////////
-
- /** FIXME this is kind of a hack */
- public class Subset extends Union {
- private final Set exclude;
- public Subset(String shortForm, Set exclude) { super(shortForm, true); this.exclude = exclude; }
- public Iterator iterator() {
- final Iterator it = Union.this.iterator();
- return new Iterator() {
- private Sequence next = it.hasNext() ? it.next() : null;
- public boolean hasNext() { return next != null; }
- public Sequence next() {
- Sequence ret = next;
- do {
- next = it.hasNext() ? it.next() : null;
- } while (next != null && (next instanceof Sequence) && exclude.contains((Sequence)next));
- return ret;
- }
- public void remove() { throw new Error(); }
- };
+
+ private void bodyToString(StringBuffer sb, String before, String between) {
+ viewed = true;
+ boolean first = true;
+ for(Sequence s : this) {
+ // FIXME: what to do here about printing out negated sequences?
+ sb.append(first ? before : between);
+ first = false;
+ sb.append(s.toString());
}
}