/** an element which can produce one of several alternatives */
public class Union extends Element implements Iterable<Sequence> {
+ /**
+ * 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).
+ *
+ * @param shortForm the "short form" display; usually
+ * @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;
+ this.synthetic = synthetic;
+ }
+
/** display form for the Union (ie not including the RHS) */
final String shortForm;
/** adds an alternative */
public void add(Sequence s) {
alternatives.add(s);
+
+ // FIXME: does this make sense?
for(Sequence n : s.needs) add(n);
for(Sequence n : s.hates) add(n);
}
- /**
- * 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).
- *
- * @param shortForm the "short form" display; usually
- * @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;
- this.synthetic = synthetic;
- }
+ // Epsilon Form //////////////////////////////////////////////////////////////////////////////
+ // FIXME
public static Union epsilon = new Union("()");
static { epsilon.add(Sequence.empty); }
+ // FIXME
private Forest.Ref epsilonForm = null;
Forest epsilonForm() {
if (epsilonForm != null) return epsilonForm;
epsilonForm = new Forest.Ref();
- for(Sequence s : this)
- if (s.possiblyEpsilon(null))
+ for(Sequence s : this) {
+ // FIXME FIXME FIXME
+ if (new Walk.Cache().possiblyEpsilon(s))
epsilonForm.merge(s.epsilonForm());
+ }
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;
+ public StringBuffer toString(StringBuffer sb) {
+ if (synthetic) return sb;
boolean first = true;
if (alternatives.size()==0) {
- sb.append(pad(15, shortForm) + "::= ");
+ sb.append(StringUtil.pad(15, shortForm) + " = ");
} else for(Sequence s : this) {
- sb.append(pad(15, first ? shortForm : "") + (first ? "::= " : " | "));
+ sb.append(StringUtil.pad(15, first ? shortForm : "") + (first ? " = " : " | "));
first = false;
sb.append(s.toString());
sb.append('\n');
}
sb.append('\n');
- }
-
- // SubUnion //////////////////////////////////////////////////////////////////////////////
-
- /** FIXME this is kind of a hack */
- public class Subset extends Union {
- private final Set<Sequence> exclude;
- public Subset(String shortForm, Set<Sequence> exclude) { super(shortForm, true); this.exclude = exclude; }
- public Iterator<Sequence> iterator() {
- final Iterator<Sequence> it = Union.this.iterator();
- return new Iterator<Sequence>() {
- 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(); }
- };
- }
+ return sb;
}
}