// Position //////////////////////////////////////////////////////////////////////////////
/** the imaginary position before or after an element of a sequence; corresponds to an "LR item" */
- public class Position {
+ public class Position implements IntegerMappable {
+
+ private Forest zero = null;
+ public Forest zero() {
+ if (zero != null) return zero;
+ if (pos > 0) throw new Error();
+ return zero = rewrite(null);
+ }
+
final int pos;
private final Position next;
}
boolean isFirst() { return pos==0; }
- boolean isRightNullable(Walk.Cache cache) {
- if (isLast()) return true;
- if (!element().possiblyEpsilon(cache)) return false;
- return next().isRightNullable(cache);
- }
/** the element immediately after this Position, or null if this is the last Position */
public Element element() { return pos>=elements.length ? null : elements[pos]; }
/** true iff this Position is the last one in the sequence */
public boolean isLast() { return next()==null; }
- // Reduction /////////////////////////////////////////////////////////////////////////////////
+ // Position /////////////////////////////////////////////////////////////////////////////////
final <T> Forest<T> rewrite(Token.Location loc) {
if (this==firstp()) return epsilonForm();
for(Position p = Sequence.this.firstp(); p != null; p = p.next()) {
ret.append(' ');
if (p==this) ret.append(" | ");
- if (p.element()!=null) ret.append(p.element().possiblyEpsilon(null) ? "["+p.element()+"]" : p.element());
+ if (p.element()!=null) ret.append(p.element());
else ret.append(' ');
}
ret.append("}>");
return ret.toString();
}
+ private final int idx = master_position_idx++;
+ public int toInt() { return idx; }
}
-
+ private static int master_position_idx = 0;
// toString //////////////////////////////////////////////////////////////////////////////