unrolling forests without recursion

[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 59ecb59..6c7a25e 100644 (file)
--- a/src/edu/berkeley/sbp/Atom.java
+++ b/src/edu/berkeley/sbp/Atom.java
@@ -11,9 +11,8 @@ import edu.berkeley.sbp.*;
 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 //////////////////////////////////////////////////////////////////////////////
 
@@ -29,30 +28,17 @@ public abstract class Atom<T> extends Element implements Topology<T> {
     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; }
-    }
-    
-    public static class Hack<T extends Token> extends Atom<T> {
-        private final Atom<T> a;
-        static final Topology leftright =
-            edu.berkeley.sbp.misc.CharToken.rightBrace.union(edu.berkeley.sbp.misc.CharToken.leftBrace);
-        public Hack(Atom<T> a) { this.a = a; }
-        public Topology<T> top() { return ((Topology<T>)a.top()).minus(leftright); }
-        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;
     }
-    
 }