checkpoint

[sbp.git] / src / edu / berkeley / sbp / Atom.java

diff --git a/src/edu/berkeley/sbp/Atom.java b/src/edu/berkeley/sbp/Atom.java
index 6c7a25e..daa3d49 100644 (file)
--- a/src/edu/berkeley/sbp/Atom.java
+++ b/src/edu/berkeley/sbp/Atom.java
@@ -7,38 +7,24 @@ import edu.berkeley.sbp.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> {
+/**
+ *  <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<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>> {
 
-    protected abstract Topology<T> top();
-    public    abstract String       toString();
-    public             StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
+    /** the set (topology) of tokens that can match this element */
+    public abstract Topology<Token>  getTokenTopology();
 
-    // Topology Thunks //////////////////////////////////////////////////////////////////////////////
+    StringBuffer toString(StringBuffer sb) { sb.append(this); return sb; }
 
-    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()); }
-
-    /** 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;
-    }
 }
 
+