--- a/src/luan/interp/LuaStateImpl.java	Thu Dec 13 02:50:04 2012 +0000
+++ b/src/luan/interp/LuaStateImpl.java	Fri Dec 14 05:40:35 2012 +0000
@@ -8,43 +8,86 @@
 final class LuaStateImpl implements LuaState {
 	private final LuaTable env = new LuaTable();
 
-	public LuaTable env() {
+	@Override public LuaTable env() {
 		return env;
 	}
 
 
-	private static class LuaStack {
-		final LuaStack previousStack;
-		final Object[] a;
+	private static class Frame {
+		final Frame previousFrame;
+		final LuaClosure closure;
+		final Object[] stack;
 		final Object[] varArgs;
+		UpValue[] downValues = null;
+
+		Frame( Frame previousFrame, LuaClosure closure, int stackSize, Object[] varArgs) {
+			this.previousFrame = previousFrame;
+			this.closure = closure;
+			this.stack = new Object[stackSize];
+			this.varArgs = varArgs;
+		}
 
-		LuaStack( LuaStack previousStack, int stackSize, Object[] varArgs) {
-			this.previousStack = previousStack;
-			this.a = new Object[stackSize];
-			this.varArgs = varArgs;
+		void stackClear(int start,int end) {
+			if( downValues != null ) {
+				for( int i=start; i<end; i++ ) {
+					UpValue downValue = downValues[i];
+					if( downValue != null ) {
+						downValue.close();
+						downValues[i] = null;
+					}
+				}
+			}
+			for( int i=start; i<end; i++ ) {
+				stack[i] = null;
+			}
+		}
+
+		UpValue getUpValue(int index) {
+			if( downValues==null )
+				downValues = new UpValue[stack.length];
+			if( downValues[index] == null )
+				downValues[index] = new UpValue(stack,index);
+			return downValues[index];
 		}
 	}
 
-	private LuaStack stack = null;
-	public Object[] returnValues;
-	public LuaClosure tailFn;
+	private Frame frame = null;
+	Object[] returnValues;
+	LuaClosure tailFn;
 
-	Object[] newStack(int stackSize, Object[] varArgs) {
-		stack = new LuaStack(stack,stackSize,varArgs);
-		return stack.a;
+	// returns stack
+	Object[] newFrame(LuaClosure closure, int stackSize, Object[] varArgs) {
+		frame = new Frame(frame,closure,stackSize,varArgs);
+		return frame.stack;
 	}
 
-	void popStack() {
+	void popFrame() {
 		returnValues = LuaFunction.EMPTY_RTN;
 		tailFn = null;
-		stack = stack.previousStack;
+		frame = frame.previousFrame;
+	}
+
+	Object stackGet(int index) {
+		return frame.stack[index];
+	}
+
+	void stackSet(int index,Object value) {
+		frame.stack[index] = value;
 	}
 
-	public Object[] stack() {
-		return stack.a;
+	void stackClear(int start,int end) {
+		frame.stackClear(start,end);
+	}
+
+	Object[] varArgs() {
+		return frame.varArgs;
 	}
 
-	public Object[] varArgs() {
-		return stack.varArgs;
+	LuaClosure closure() {
+		return frame.closure;
+	}
+
+	UpValue getUpValue(int index) {
+		return frame.getUpValue(index);
 	}
 }