+// Copyright 2006 all rights reserved; see LICENSE file for BSD-style license
+
package edu.berkeley.sbp;
import java.io.*;
import java.util.*;
import edu.berkeley.sbp.*;
import edu.berkeley.sbp.*;
-/** an element which matches exactly one input token */
-public abstract class Atom<T> extends Element implements Topology<T> {
-
- protected abstract Topology<T> top();
- public abstract String toString();
- public StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
-
- // Topology Thunks //////////////////////////////////////////////////////////////////////////////
-
- public Topology<T> unwrap() { return top().unwrap(); }
- public Topology<T> empty() { return top().empty(); }
- public boolean contains(T v) { return top().contains(v); }
- 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); }
- public int hashCode() { return top().hashCode(); }
- public boolean equals(Object o) { return o != null && o instanceof Atom && ((Atom)o).top().equals(top()); }
+/**
+ * <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 <a
+ * href=http://en.wikipedia.org/wiki/Frege>Frege'd</a> up) so that
+ * Atoms can be intersected and unioned with each other to result in
+ * other Atom<Token>'s (rather than raw Topology<Token>'s, which are
+ * not Elements). If you want the latter, use the getTokenTopology()
+ * method.
+ * </p>
+ */
+public abstract class Atom<Token> extends Element implements Topology<Atom<Token>> {
+
+ /** the set (topology) of tokens that can match this element */
+ public abstract Topology<Token> getTokenTopology();
+
+ StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
- // Subclasses //////////////////////////////////////////////////////////////////////////////
-
- /** an atom which tracks the possible tokenset of some element, provided that element can only match single-token sequences */
- public static class Infer<T extends Input> extends Atom<T> {
- private final Element e;
- public Infer(Element e) { this.e = e; }
- public Topology<T> top() { return (Topology<T>)toAtom(e); }
- public String toString() { return e.toString(); }
- }
-
- /** an atom which tracks the inverse of some other atom */
- public static class Invert<T extends Input> 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; }
- }
-
- 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;
- }
}
+