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 /** <font color=green>an element which can produce one of several alternatives</font> */
11 public class Union extends Element implements Iterable<Sequence> {
13 private final String name;
14 private final boolean synthetic;
16 private final List<Sequence> alternatives = new ArrayList<Sequence>();
18 public Union(String name) { this(name, false); }
21 * Since every cycle in a non-degenerate grammar contains at
22 * least one Union, every instance of this class must be able to
23 * display itself in both "long form" (list of the long forms of
24 * its alternatives) and "short form" (some name).
26 * @param shortForm the "short form" display; for display purposes only
27 * @param synthetic if true, this Union's "long form" is "obvious" and should not be displayed when printing the grammar
29 public Union(String name, boolean synthetic) {
31 this.synthetic = synthetic;
34 public boolean contains(Sequence s) { return alternatives.contains(s); }
35 public Iterator<Sequence> iterator() { return alternatives.iterator(); }
37 /** adds an alternative */
38 public void add(Sequence s) {
39 if (alternatives.contains(s)) return;
44 // Epsilon Form //////////////////////////////////////////////////////////////////////////////
47 private Forest.Many epsilonForm = null;
48 Forest epsilonForm() {
49 if (epsilonForm != null) return epsilonForm;
50 epsilonForm = new Forest.Many();
51 for(Sequence s : this) {
53 if (new Walk.Cache().possiblyEpsilon(s))
54 epsilonForm.merge(s.epsilonForm());
60 // Display //////////////////////////////////////////////////////////////////////////////
62 public String getName() {
63 if (name != null) return name;
64 return "(anon_union)";
66 public String toString() {
67 if (name != null) return name;
68 StringBuffer sb = new StringBuffer();
70 bodyToString(sb, "", " | ");
74 public StringBuffer toString(StringBuffer sb) {
75 if (synthetic) return sb;
77 String before = StringUtil.pad(15, getName()) + " = ";
78 if (alternatives.size()==0) {
83 "\n" + StringUtil.pad(15, "") + " | ");
89 private void bodyToString(StringBuffer sb, String before, String between) {
91 for(Sequence s : this) {
92 // FIXME: what to do here about printing out negated sequences?
93 sb.append(first ? before : between);
95 sb.append(s.toString());