////////////////////////////////////////////////////////////////////////////////
- public Topology noFollow() { return null; }
+ public Element noFollow = null;
+ public final Topology noFollow() { return noFollow==null ? null : noFollow.toAtom(); }
Topology toAtom() {
- if (elements.length>1) throw new RuntimeException("cannot invoke toAtom() on a Sequence with " + elements.length + " elements: " + this);
- if (elements.length==0) return null;
+ if (elements.length!=1) throw new RuntimeException("cannot invoke toAtom() on a Sequence with " + elements.length + " elements: " + this);
return elements[0].toAtom();
}
protected Sequence(Element[] elements, HashSet<Sequence> and, HashSet<Sequence> not) {
this.needs = and==null ? new HashSet<Sequence>() : and;
this.hates = not==null ? new HashSet<Sequence>() : not;
- //for(Sequence s : needs) s.lame = true;
- //for(Sequence s : hates) s.lame = true;
this.elements = elements;
this.firstp = new Position(0);
}
- void reachable(HashSet<Position> h) { firstp().reachable(h); }
-
- Forest epsilonForm() { return firstp().rewrite(null); }
+ // DO NOT MESS WITH THE FOLLOWING LINE!!!
+ private Forest.Ref epsilonForm = null;
+ private boolean eps = false;
+ Forest epsilonForm() {
+ if (epsilonForm==null) {
+ epsilonForm = new Forest.Ref();
+ Forest fo = firstp().rewrite(null);
+ epsilonForm.merge(fo);
+ }
+ return epsilonForm;
+ }
protected abstract <T> Forest<T> postReduce(Token.Location loc, Forest<T>[] args);
/** the imaginary position before or after an element of a sequence; corresponds to an "LR item" */
public class Position {
- void reachable(HashSet<Position> h) {
- if (h.contains(this)) return;
- h.add(this);
- if (element() != null) element().reachable(h);
- }
-
final int pos;
private final Position next;
final Forest[] holder;
// Reduction /////////////////////////////////////////////////////////////////////////////////
- <T> Forest<T> rewrite(Token.Location loc) {
+ final <T> Forest<T> rewrite(Token.Location loc) {
+ if (this==firstp() && eps) return epsilonForm;
+ eps = true;
for(int i=pos; i<elements.length; i++) if (holder[i]==null) holder[i] = elements[i].epsilonForm();
Forest<T> ret = Sequence.this.postReduce(loc, holder);
for(int k=0; k<pos; k++) holder[k] = null; // to help GC
+ if (this==firstp()) { if (epsilonForm==null) epsilonForm=new Forest.Ref(); epsilonForm.merge(ret); return epsilonForm; }
return ret;
}
Forest<T>[] args2 = new Forest[count];
int j = 0;
for(int i=0; i<args.length; i++) if (!drops[i]) args2[j++] = args[i];
+ //System.out.println("reduce \""+tag+"\"");
return Forest.create(loc, (T)tag, args2, this, false, false);
}
public StringBuffer toString(StringBuffer sb, boolean spacing) {