import edu.berkeley.sbp.*;
/** an element which matches exactly one input token */
-public abstract class Atom<T extends Token> extends Element implements Topology<T> {
+public abstract class Atom<T> extends Element implements Topology<T> {
protected abstract Topology<T> top();
- public abstract String toString();
-
- public Topology toAtom() { return this; }
+ public abstract String toString();
+ public StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
// Topology Thunks //////////////////////////////////////////////////////////////////////////////
public int hashCode() { return top().hashCode(); }
public boolean equals(Object o) { return o != null && o instanceof Atom && ((Atom)o).top().equals(top()); }
- // Subclasses //////////////////////////////////////////////////////////////////////////////
-
- public static class Infer<T extends Token> extends Atom<T> {
- private final Element e;
- public Infer(Element e) { this.e = e; }
- public Topology<T> top() { return (Topology<T>)e.toAtom(); }
- public String toString() { return e.toString(); /* FIXME should be toAtom() */ }
- }
-
- public static class Invert<T extends Token> extends Atom<T> {
- private final Atom<T> a;
- public Invert(Atom<T> a) { this.a = a; }
- public Topology<T> top() { return ((Topology<T>)a.top()).complement(); }
- public String toString() { return "~"+a; }
+ /** if all expressions matching <tt>e</tt> are exactly one token
+ * long, <b>attempt to</b> return an Atom representing that token
+ * (undecidable in general; only works in trivial cases)
+ */
+ public static Topology toAtom(Element e) {
+ if (e instanceof Atom) return (Atom)e;
+ if (e instanceof Sequence) return ((Sequence)e).toAtom();
+ Topology ret = null;
+ for(Sequence s : (Union)e)
+ ret = ret==null ? toAtom(s) : ret.union(s.toAtom());
+ return ret;
}
-
}