import edu.berkeley.sbp.*;
import edu.berkeley.sbp.*;
-/** an element which matches exactly one input token */
-public abstract class Atom<T extends Token> extends Element implements Topology<T> {
+/**
+ * <font color=green>an element which matches some set of one-token-long input strings</font>.
+ *
+ * <p>
+ * This class is a topology over itself (yes, that's sort of Frege'd
+ * up) so that Atoms can be intersected and unioned with each other
+ * to result in other Atom<T>'s (rather than raw Topology<T>'s, which
+ * are not Elements). If you want the latter, use the
+ * getTokenTopology() method.
+ * </p>
+ */
+public abstract class Atom<T> extends Element implements Topology<Atom<T>> {
+
+ /** the set (topology) of tokens that can match this element */
+ public abstract Topology<T> getTokenTopology();
+
+ StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
- protected abstract Topology<T> top();
-
- public Topology toAtom() { return dup(); }
-
- /** equality is based on the underlying <tt>Topology</tt> */
- public int hashCode() { return top().hashCode(); }
-
- /** equality is based on the underlying <tt>Topology</tt> */
- public boolean equals(Object o) { return o != null && o instanceof Atom && ((Atom)o).top().equals(top()); }
-
- /** declared abstract to force subclasses to override it in a useful manner */
- public abstract String toString();
-
- // Topology Thunks //////////////////////////////////////////////////////////////////////////////
-
- public void add(Topology<T> t) { top().add(t); }
- public void add(T t) { top().add(t); }
- public void remove(Topology<T> t) { top().remove(t); }
- public void remove(T t) { top().remove(t); }
- public Topology<T> dup() { return top().dup(); }
- public boolean contains(T v) { return top().contains(v); }
- public Topology<T> fresh() { return top().fresh(); }
- public Topology<T> intersect(Topology<T> t) { return top().intersect(t); }
- public Topology<T> minus(Topology<T> t) { return top().minus(t); }
- public Topology<T> union(Topology<T> t) { return top().union(t); }
- public Topology<T> complement() { return top().complement(); }
- public boolean disjoint(Topology<T> t) { return top().disjoint(t); }
- public boolean containsAll(Topology<T> t) { return top().containsAll(t); }
-
- // 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(); }
- }
-
- 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; }
- }
-
}
+