protected abstract Topology<T> top();
public abstract String toString();
+ public StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
// Topology Thunks //////////////////////////////////////////////////////////////////////////////
/** the root superclass for all components of the grammar (terminals, nonterminals, literals, etc) */
public abstract class Element {
+ abstract StringBuffer toString(StringBuffer sb);
+
/** if this element always matches exactly one token, return a topology covering exactly those possible tokens, otherwise <tt>null</tt> */
- Forest epsilonForm() { throw new Error("no epsilon form: " + this); }
- final boolean possiblyEpsilon(Walk.Cache cache) {
- Boolean ret = cache==null ? null : cache.possiblyEpsilon.get(this);
- if (ret != null) return ret.booleanValue();
- ret = new Walk.PossiblyEpsilon().walk(this) ? Boolean.TRUE : Boolean.FALSE;
- if (cache != null) cache.possiblyEpsilon.put(this, ret);
- return ret;
- }
+ Forest epsilonForm() { return null; }
+
}
else state.invokeReductions(token, this, this, n2);
}
+ public void performEmptyReductions() { state.invokeReductions(token, this, null, null); }
public final void invoke(Position r, Node n, Node n2) {
if (n==null || n2==null || r.pos==0) {
if (r.pos==0) {
target.newNode(this, result, state0, r.pos<=0, r);
}
- public void performEmptyReductions() { state.invokeReductions(token, this, null, null); }
-
private Node(Node parent, Forest pending, State state) {
this.state = state;
this.holder().merge(pending);
private boolean isRightNullable(Position p) {
if (p.isLast()) return true;
- if (!p.element().possiblyEpsilon(this)) return false;
+ if (!possiblyEpsilon(p.element())) return false;
return isRightNullable(p.next());
}
// 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();
- epsilonForm.merge(firstp().rewrite2(null));
- }
+ if (epsilonForm!=null) return epsilonForm;
+ epsilonForm = new Forest.Ref();
+ epsilonForm.merge(firstp().rewrite(null, false));
return epsilonForm;
}
// Position /////////////////////////////////////////////////////////////////////////////////
- final <T> Forest<T> rewrite(Input.Location loc) {
- if (this==firstp()) return epsilonForm();
- return rewrite2(loc);
- }
-
- final <T> Forest<T> rewrite2(Input.Location loc) {
+ final <T> Forest<T> rewrite(Input.Location loc) { return rewrite(loc, true); }
+ private final <T> Forest<T> rewrite(Input.Location loc, boolean epsilonCheck) {
+ if (epsilonCheck && this==firstp()) return epsilonForm();
for(int i=0; i<pos; i++) if (holder[i]==null) throw new Error("realbad " + i);
for(int i=pos; i<elements.length; i++) {
if (holder[i]==null) holder[i] = elements[i].epsilonForm();
/** 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;
}
}
public Topology<Tok> sequence(Sequence seq) {
for(Position p = seq.firstp(); p!=null && !p.isLast(); p = p.next()) {
walk(p.element());
- if (!p.element().possiblyEpsilon(c)) break;
+ if (!c.possiblyEpsilon(p.element())) break;
}
return cs;
}
Position mp = null;
for(Position pos = a.firstp(); pos != null && !pos.isLast(); pos = pos.next()) {
if (matched) cs = cs.union(c.first(pos.element(), cs.empty()));
- if (pos.isLast()) { matched = (matched && pos.element().possiblyEpsilon(c)); continue; }
+ if (pos.isLast()) { matched = (matched && c.possiblyEpsilon(pos.element())); continue; }
boolean good = false;
if (e instanceof Atom) {
Topology top = c.atoms.get(pos.element());
public <Tok extends Input> Topology<Tok> first(Element e, Topology<Tok> empty) {
return new Walk.First<Tok>(empty, this).walk(e);
}
+ final boolean possiblyEpsilon(Element e) {
+ Walk.Cache cache = this;
+ Boolean ret = possiblyEpsilon.get(e);
+ if (ret != null) return ret.booleanValue();
+ ret = new Walk.PossiblyEpsilon().walk(e) ? Boolean.TRUE : Boolean.FALSE;
+ possiblyEpsilon.put(e, ret);
+ return ret;
+ }
}
}
} else {
if (keeping) drops[i] = true;
}
- if (oi==SELF) o2[j] = u.new Subset("(("+u+"))", set);
- else o2[j] = (Element)oi;
+ /*if (oi==SELF) o2[j] = u.new Subset("(("+u+"))", set);
+ else*/ o2[j] = (Element)oi;
if (MetaGrammar.dropAll.contains(o2[j])) drops[j] = true;
nonDrop += drops[j] ? 0 : 1;
/** miscellaneous string utilities */
public class StringUtil {
+ public static String pad(int i,String s) {
+ return s.length() >= i ? s : pad(i-1,s)+" ";
+ }
+
public static String join(String[] s, String sep) {
StringBuffer ret = new StringBuffer();
for(int i=0; i<s.length; i++) {
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