diff --git a/lib/h2-scheme-execute-apply.adb b/lib/h2-scheme-execute-apply.adb
index d85abb1..0c02e1d 100644
--- a/lib/h2-scheme-execute-apply.adb
+++ b/lib/h2-scheme-execute-apply.adb
@@ -27,8 +27,7 @@ Ada.Text_IO.Put_Line ("EXPECTED CONS-CELL FOR CAR");
 			raise Evaluation_Error;
 		end if;
 
-		Pop_Frame (Interp); -- Done with the current frame
-		Put_Frame_Result (Interp, Interp.Stack, Get_Car(A));
+		Return_Frame (Interp, Get_Car(A)); 
 	end Apply_Car_Procedure;
 
 	procedure Apply_Cdr_Procedure is
@@ -46,8 +45,7 @@ Ada.Text_IO.Put_Line ("EXPECTED CONS-CELL FOR CDR");
 			raise Evaluation_Error;
 		end if;
 
-		Pop_Frame (Interp); -- Done with the current frame
-		Put_Frame_Result (Interp, Interp.Stack, Get_Cdr(A));
+		Return_Frame (Interp, Get_Cdr(A));
 	end Apply_Cdr_Procedure;
 
 	procedure Apply_Cons_Procedure is
@@ -64,8 +62,7 @@ Ada.Text_IO.Put_Line ("WRONG NUMBER OF ARGUMETNS FOR CONS");
 		B := Get_Car(Get_Cdr(Ptr)); -- the second argument
 		Ptr := Make_Cons (Interp.Self, A, B); -- change car
 
-		Pop_Frame (Interp); -- Done with the current frame
-		Put_Frame_Result (Interp, Interp.Stack, Ptr);
+		Return_Frame (Interp, Ptr);
 	end Apply_Cons_Procedure;
 
 	procedure Apply_Setcar_Procedure is
@@ -86,8 +83,7 @@ Ada.Text_IO.Put_Line ("EXPECTED CONS-CELL FOR Setcar");
 		B := Get_Car(Get_Cdr(Ptr)); -- the second argument
 		Set_Car (A, B); -- change car
 
-		Pop_Frame (Interp); -- Done with the current frame
-		Put_Frame_Result (Interp, Interp.Stack, A);
+		Return_Frame (Interp, A);
 	end Apply_Setcar_Procedure;
 
 	procedure Apply_Setcdr_Procedure is
@@ -108,8 +104,7 @@ Ada.Text_IO.Put_Line ("EXPECTED CONS-CELL FOR Setcdr");
 		B := Get_Car(Get_Cdr(Ptr)); -- the second argument
 		Set_Cdr (A, B); -- change cdr
 
-		Pop_Frame (Interp); -- Done with the current frame
-		Put_Frame_Result (Interp, Interp.Stack, A);
+		Return_Frame (Interp, A);
 	end Apply_Setcdr_Procedure;
 
 	-- -------------------------------------------------------------
@@ -132,8 +127,7 @@ Ada.Text_IO.Put ("NOT INTEGER FOR ADD"); Print (Interp, Car);
 			Ptr := Get_Cdr(Ptr);
 		end loop;
 
-		Pop_Frame (Interp); -- Done with the current frame
-		Put_Frame_Result (Interp, Interp.Stack, Integer_To_Pointer(Num));
+		Return_Frame (Interp, Integer_To_Pointer(Num));
 	end Apply_Add_Procedure;
 
 	procedure Apply_Subtract_Procedure is
@@ -161,8 +155,7 @@ Ada.Text_IO.Put ("NOT INTEGER FOR ADD"); Print (Interp, Car);
 			end loop;
 		end if;
 
-		Pop_Frame (Interp); --  Done with the current frame
-		Put_Frame_Result (Interp, Interp.Stack, Integer_To_Pointer(Num));
+		Return_Frame (Interp, Integer_To_Pointer(Num));
 	end Apply_Subtract_Procedure;
 
 	procedure Apply_Multiply_Procedure is
@@ -182,8 +175,7 @@ Ada.Text_IO.Put ("NOT INTEGER FOR MULTIPLY"); Print (Interp, Car);
 			Ptr := Get_Cdr(Ptr);
 		end loop;
 
-		Pop_Frame (Interp); -- Done with the current frame
-		Put_Frame_Result (Interp, Interp.Stack, Integer_To_Pointer(Num));
+		Return_Frame (Interp, Integer_To_Pointer(Num));
 	end Apply_Multiply_Procedure;
 
 	procedure Apply_Quotient_Procedure is
@@ -203,8 +195,7 @@ Ada.Text_IO.Put ("NOT INTEGER FOR MULTIPLY"); Print (Interp, Car);
 			Ptr := Get_Cdr(Ptr);
 		end loop;
 
-		Pop_Frame (Interp); -- Done with the current frame
-		Put_Frame_Result (Interp, Interp.Stack, Integer_To_Pointer(Num));
+		Return_Frame (Interp, Integer_To_Pointer(Num));
 	end Apply_Quotient_Procedure;
 
 	generic 
@@ -241,8 +232,7 @@ Ada.Text_IO.Put ("NOT INTEGER FOR MULTIPLY"); Print (Interp, Car);
 				Ptr := Get_Cdr(Ptr);
 			end loop;
 
-			Pop_Frame (Interp); --  Done with the current frame
-			Put_Frame_Result (Interp, Interp.Stack, Bool);
+			Return_Frame (Interp, Bool);
 		else
 Ada.Text_IO.Put_line ("TOO FEW ARGUMETNS FOR COMPARISON");
 			raise Syntax_Error;
@@ -359,9 +349,7 @@ Ada.Text_IO.Put_line ("TOO FEW ARGUMETNS FOR COMPARISON");
 			end if;
 		end if;
 			
-		Set_Frame_Opcode (Interp.Stack, Opcode_Grouped_Call);
-		Set_Frame_Operand (Interp.Stack, Fbody);
-		Clear_Frame_Result (Interp.Stack);
+		Switch_Frame (Interp.Stack, Opcode_Grouped_Call, Fbody, Nil_Pointer);
 
 		Pop_Tops (Interp, 4);
 	end Apply_Closure;
@@ -404,48 +392,28 @@ Ada.Text_IO.Put_line ("TOO FEW ARGUMETNS FOR COMPARISON");
 			raise Syntax_Error;
 		end if; 
 
-		Push_Top (Interp, C'Unchecked_Access);
-		C := Get_Frame_Parent(Interp.Stack);
+		Push_Top (Interp, C'Unchecked_Access); -- this is not needed. TOOD: remove this
+		C := Make_Continuation (Interp.Self, Get_Frame_Parent(Interp.Stack));
 declare
+p: object_Pointer := get_frame_parent(interp.stack);
 w: object_word;
-for w'address use c'address;
-
-f: object_word;
-for f'address use interp.stack'address;
-
-r: object_pointer := get_frame_result(c);
+for w'address use p'address;
 begin
-ada.text_io.put_line ("Frame" & object_word'image(f) & " " & Opcode_Type'Image(Get_Frame_Opcode(Interp.Stack)));
-ada.text_io.put ("                      CURRENT RESULT ");
-print (interp, r);
-ada.text_io.put_line ("                      PARENT FRAME " & object_word'image(w));
+ada.text_io.put_line ("making continuatination to " & object_word'image(w) & " opcode " & opcode_type'image(get_frame_opcode(p)));
+print (interp, get_Frame_operand(p));
+print (interp, get_Frame_intermediate(p));
+ada.text_io.put_line ("-----------------");
 end;
-
-		C := Make_Continuation (Interp.Self, C);
-		C := Make_Cons (Interp.Self, C, Nil_Pointer);
-		C := Make_Cons (Interp.Self, Get_Car(Args), C);
-declare
-w: object_word;
-for w'address use c'address;
-f: object_word;
-for f'address use interp.stack'address;
-begin
-ada.text_io.put ("                      PUSH CONTINUATION ");
-ada.text_io.put (object_word'image(w) & " ");
-print (interp, c);
-end;
-
 		Set_Frame_Opcode (Interp.Stack, Opcode_Apply);
-		Set_Frame_Operand (Interp.Stack, C);
+		Set_Frame_Operand (Interp.Stack, Get_Car(Args)); -- (call/cc xxx), xxx becomes this.
+		Set_Frame_Intermediate (Interp.Stack, Nil_Pointer); -- pass the continuation object
+		Chain_Frame_Intermediate (Interp, Interp.Stack, C); -- as an actual parameter. (xxx #continuation)
 		Clear_Frame_Result (Interp.Stack);
 
-ada.text_io.put_line ("                      CLEARED RESULT BEFORE APPLYING");
-
 		Pop_Tops (Interp, 1);
 	end Apply_Callcc_Procedure;
 
 	procedure Apply_Continuation is
-		R: Object_Pointer;
 	begin
 declare
 w: object_word;
@@ -465,12 +433,9 @@ Print (Interp, get_Frame_result(interp.stack));
 			raise Syntax_Error;
 		end if;
 
--- Get the result of the continuation frame
---		R := Get_Frame_Result(Interp.Stack);
-
           -- Restore the frame to the remembered one
-          Interp.Stack := Get_Continuation_Frame(Func);
-
+		Interp.Stack := Get_Continuation_Frame(Func);
+	
 declare
 f: object_word;
 for f'address use interp.stack'address;
@@ -480,32 +445,16 @@ ada.text_io.put ("                      CURRENT RESULT " );
 print (interp, get_Frame_result(interp.stack));
 ada.text_io.put ("                      CURRENT OPERAND " );
 print (interp, get_Frame_operand(interp.stack));
+ada.text_io.put ("                      CURRENT INTERMEDIATE " );
+print (interp, get_Frame_intermediate(interp.stack));
 ada.text_io.put_line ("                      CURRENT OPCODE " & opcode_type'image(get_Frame_opcode(interp.stack)));
 end;
 
-
-ada.text_io.put ("                      CHAIN NEW RESULT, TAKING THE FIRST ONLY FROM ");
-print (interp, args);
-		Put_Frame_Result (Interp, Interp.Stack, Get_Car(Args)); 
-
---		if R /= Nil_Pointer then
---ada.text_io.put ("                      CARRY OVER RESULT ");
---print (interp, get_car(r));
---			Chain_Frame_Result (Interp, Interp.Stack, Get_Car(R));
---		end if;
-
---Set_Frame_Result (Interp.Stack, R);
---Chain_Frame_Result (Interp, Interp.Stack, Get_Car(Args)); 
-
+		Set_Frame_Result (Interp.Stack, Get_Car(Args)); 
 
 ada.text_io.put ("                      FINAL RESULT ");
 print (interp, get_Frame_result(interp.stack));
 
---		if Get_Frame_Parent(Interp.Stack) /= Nil_Pointer then
---			Set_Frame_Result (Get_Frame_Parent(Interp.Stack), Get_Continuation_Save(Func));
---			--Set_Frame_Operand (Get_Frame_Parent(Interp.Stack), Get_Continuation_Save2(Func));
---		end if;
-
 	end Apply_Continuation;
 
 begin
@@ -514,7 +463,7 @@ begin
 	Push_Top (Interp, Args'Unchecked_Access);
 
 	Operand := Get_Frame_Operand(Interp.Stack);
-	pragma Assert (Is_Cons(Operand));
+--	pragma Assert (Is_Cons(Operand));
 
 declare
 w: object_word;
@@ -526,13 +475,15 @@ print (Interp, Operand);
 ada.text_io.put ("                      CURRENT RESULT => ");
 print (Interp, get_frame_result(interp.stack));
 end;
-	Func := Get_Car(Operand);
+--	Func := Get_Car(Operand);
+Func := Get_Frame_Operand(Interp.Stack);
 	if not Is_Normal_Pointer(Func) then
 		Ada.Text_IO.Put_Line ("INVALID FUNCTION TYPE");
 		raise Evaluation_Error;
 	end if;
 
-	Args := Get_Cdr(Operand);
+--	Args := Get_Cdr(Operand);
+Args := Get_Frame_Intermediate(Interp.Stack);
 
 	case Func.Tag is
 		when Procedure_Object => 
diff --git a/lib/h2-scheme-execute-evaluate.adb b/lib/h2-scheme-execute-evaluate.adb
index ad3df25..7511227 100644
--- a/lib/h2-scheme-execute-evaluate.adb
+++ b/lib/h2-scheme-execute-evaluate.adb
@@ -24,8 +24,7 @@ procedure Evaluate is
 		Operand := Cdr;  -- Skip "And"
 		if Operand = Nil_Pointer then
 			-- (and)
-			Pop_Frame (Interp); 
-			Put_Frame_Result (Interp, Interp.Stack, V);
+			Return_Frame (Interp, V);
 		elsif not Is_Cons(Operand) or else Get_Last_Cdr(Operand) /= Nil_Pointer then
 			-- (and . 10)
 			-- (and 1 2 . 10)
@@ -213,13 +212,8 @@ Ada.Text_IO.Put_Line ("NO ALTERNATE");
 			raise Syntax_Error;
 		end if;
 
-		declare
-			Closure: Object_Pointer;
-		begin
-			Closure := Make_Closure(Interp.Self, Operand, Get_Frame_Environment(Interp.Stack));
-			Pop_Frame (Interp);  -- Done
-			Put_Frame_Result (Interp, Interp.Stack, Closure);
-		end;
+		-- Create a closure object and return it the the upper frame.
+		Return_Frame (Interp, Make_Closure(Interp.Self, Operand, Get_Frame_Environment(Interp.Stack)));
 	end Evaluate_Lambda_Syntax;
 
 	procedure Check_Let_Syntax is
@@ -418,8 +412,7 @@ Ada.Text_IO.Put_Line ("NO ALTERNATE");
 			Ada.Text_IO.Put_LINE ("WRONG NUMBER OF ARGUMENTS FOR QUOTE");
 			raise Syntax_Error;
 		end if;
-		Pop_Frame (Interp);	 -- Done
-		Put_Frame_Result (Interp, Interp.Stack, Get_Car(Operand));
+		Return_Frame (Interp, Get_Car(Operand));
 	end Evaluate_Quote_Syntax;
 
 	procedure Evaluate_Set_Syntax is
@@ -448,12 +441,12 @@ Ada.Text_IO.Put_Line ("NO ALTERNATE");
 			Cdr := Get_Car(Cdr); -- <expression>
 
 			-- Arrange to finish setting a variable after <expression> evaluation.
-			--Switch_Frame (Interp.Stack, Opcode_Set_Finish, Car);
+			--Switch_Frame (Interp.Stack, Opcode_Set_Finish, Car, Nil_Pointer);
 			-- Arrange to evalaute the value part
 			--Push_Frame (Interp, Opcode_Evaluate_Object, Cdr); 
 
 			-- These 2 lines derives the same result as the 2 lines commented out above.
-			Switch_Frame (Interp.Stack, Opcode_Evaluate_Object, Cdr);
+			Switch_Frame (Interp.Stack, Opcode_Evaluate_Object, Cdr, Nil_Pointer);
 			Push_Subframe (Interp, Opcode_Set_Finish, Car); 
 		else
 			Ada.Text_IO.Put_LINE ("INVALID SYMBOL AFTER SET!");
@@ -518,16 +511,15 @@ end;
 
 						if Operand = Nil_Pointer then
 							-- (begin)
-							Pop_Frame (Interp);	
 							-- Return nil to the upper frame for (begin).
-							Put_Frame_Result (Interp, Interp.Stack, Nil_Pointer);
+							Return_Frame (Interp, Nil_Pointer);
 						else
 							if Get_Last_Cdr(Operand) /= Nil_Pointer then
 								Ada.Text_IO.Put_LINE ("FUCKNING CDR FOR BEGIN");
 								raise Syntax_Error;
 							end if;
 
-							Switch_Frame (Interp.Stack, Opcode_Grouped_Call, Operand);
+							Switch_Frame (Interp.Stack, Opcode_Grouped_Call, Operand, Nil_Pointer);
 						end if;
 
 						--if (Interp.Trait.Trait_Bits and No_Optimization) = 0 then
@@ -580,7 +572,7 @@ end;
 				end if;
 
 				-- Switch the current frame to evaluate <operator>
-				Switch_Frame (Interp.Stack, Opcode_Evaluate_Object, Car);
+				Switch_Frame (Interp.Stack, Opcode_Evaluate_Object, Car, Nil_Pointer);
 
 				-- Push a new frame to evaluate arguments.
 				Push_Subframe (Interp, Opcode_Procedure_Call, Cdr);
@@ -593,7 +585,6 @@ end;
 	goto Done;
 
 <<Literal>>
-	Pop_Frame (Interp); -- done
 declare
 w: object_word;
 for w'address use operand'address;
@@ -601,7 +592,7 @@ begin
 Ada.Text_IO.Put ("Return => (" & object_word'image(w) & ") =>" );
 Print (Interp, Operand);
 end;
-	Put_Frame_Result (Interp, Interp.Stack, Operand);
+	Return_Frame (Interp, Operand);
 	goto Done;
 
 <<Done>>
diff --git a/lib/h2-scheme-execute.adb b/lib/h2-scheme-execute.adb
index 89f1777..828c36d 100644
--- a/lib/h2-scheme-execute.adb
+++ b/lib/h2-scheme-execute.adb
@@ -43,8 +43,7 @@ procedure Execute (Interp: in out Interpreter_Record) is
 			Push_Frame (Interp, Opcode_Evaluate_Object, Get_Car(X));
 		else
 			-- Return the result of the last expression evaluated.
-			Pop_Frame (Interp);
-			Put_Frame_Result (Interp, Interp.Stack, Y);
+			Return_Frame (Interp, Y);
 		end if;
 	end Evaluate_Up_To;
 
@@ -54,30 +53,27 @@ procedure Execute (Interp: in out Interpreter_Record) is
 
 	procedure Finish_Define_Symbol is
 		pragma Inline (Finish_Define_Symbol);
-		X: aliased Object_Pointer;
+		X: Object_Pointer;
 		Y: aliased Object_Pointer;
 	begin
-		Push_Top (Interp, X'Unchecked_Access);
-		Push_Top (Interp, Y'Unchecked_Access);
+		-- Keep Y managed as Y is referenced beyond the gc point. 
+		Push_Top (Interp, Y'Unchecked_Access); 
 
 		X := Get_Frame_Operand(Interp.Stack); -- symbol
 		pragma Assert (Is_Symbol(X));
 
 		Y := Get_Frame_Result(Interp.Stack);  -- value list
 
-		Put_Environment (Interp, X, Y);
+		Put_Environment (Interp, X, Y);  -- gc point
 
-		Pop_Frame (Interp);     -- Done
-		Put_Frame_Result (Interp, Interp.Stack, Y);
-
-		Pop_Tops (Interp, 2);
+		Return_Frame (Interp, Y); -- Y is referenced here.
+		Pop_Tops (Interp, 1); -- Unmanage Y
 	end Finish_Define_Symbol;
 
 	procedure Finish_If_Syntax is
 		pragma Inline (Finish_If_Syntax);
 		X: aliased Object_Pointer;
 		Y: aliased Object_Pointer;
-		Z: aliased Object_Pointer;
 	begin
 		Push_Top (Interp, X'Unchecked_Access);
 		Push_Top (Interp, Y'Unchecked_Access);
@@ -97,9 +93,8 @@ procedure Execute (Interp: in out Interpreter_Record) is
 				Set_Frame_Operand (Interp.Stack, Get_Car(X));
 				Clear_Frame_Result (Interp.Stack);
 			else
-				Pop_Frame (Interp);
 				-- Return nil if no <alternate> is specified
-				Put_Frame_Result (Interp, Interp.Stack, Nil_Pointer);
+				Return_Frame (Interp, Nil_Pointer);
 			end if;
 		else
 			-- All values except #f are true values. evaluate <consequent>
@@ -117,27 +112,66 @@ procedure Execute (Interp: in out Interpreter_Record) is
 
 	procedure Do_Procedure_Call is
 		pragma Inline (Do_Procedure_Call);
-		X: aliased Object_Pointer;
-		R: aliased Object_Pointer;
+		R: Object_Pointer;
+		X: Object_Pointer;
 	begin
-		Push_Top (Interp, X'Unchecked_Access);
-		Push_Top (Interp, R'Unchecked_Access);
-
-		X := Get_Frame_Operand(Interp.Stack);
+		-- Note: if you change the assignment order of R and X, 
+		--       Push_Top() and Pop_Tops() are needed.
+		--Push_Top (Interp, X'Unchecked_Access);
+		--Push_Top (Interp, R'Unchecked_Access);
 		R := Make_Cons(Interp.Self, Get_Frame_Result(Interp.Stack), Get_Frame_Intermediate(Interp.Stack));
+		X := Get_Frame_Operand(Interp.Stack);
 
 		if Is_Cons(X) then
-			Switch_Frame (Interp.Stack, Opcode_Evaluate_Object, Get_Car(X));
+			Switch_Frame (Interp.Stack, Opcode_Evaluate_Object, Get_Car(X), Nil_Pointer);
 			Push_Subframe_With_Intermediate (Interp, Opcode_Procedure_Call, Get_Cdr(X), R);
 		else
 			-- no more argument to evaluate. 
 			-- apply the evaluated arguments to the evaluated operator.
-			Switch_Frame (Interp.Stack, Opcode_Apply, Reverse_Cons(R));
+			R := Reverse_Cons(R);
+
+--ada.text_io.put_line ("xxxxxxxxxxxxxxxxxx");
+--print (interp, r);
+--print (interp, get_car(r));
+--print (interp, get_cdr(r));
+--ada.text_io.put_line ("xxxxxxxxxxxxxxxxxx");
+
+			-- This frame can be resumed. Switching the current frame to Opcode_Apply
+			-- affects continuation objects that point to the current frame. However,
+			-- keeping it unchanged causes this frame to repeat actions that has been 
+			-- taken previously when it's resumed. So i change the frame to something 
+			-- special designed for continuation only.
+			Switch_Frame (Interp.Stack, Opcode_Procedure_Call_Finish, Get_Car(R), Nil_Pointer);
+			Pop_Frame (Interp);
+
+			-- Replace the current frame popped by a new applying frame.
+			Push_Frame_With_Intermediate (Interp, Opcode_Apply, Get_Car(R), Get_Cdr(R));
 		end if;
 
-		Pop_Tops (Interp, 2);
+		--Pop_Tops (Interp, 2);
 	end Do_Procedure_Call;
 
+	procedure Do_Procedure_Call_Finish is
+		pragma Inline (Do_Procedure_Call_Finish);
+		R: Object_Pointer;
+		X: Object_Pointer;
+	begin
+		-- TODO: is this really correct? verify this.
+
+		-- Note: if you change the assignment order of R and X, 
+		--       Push_Top() and Pop_Tops() are needed.
+		--Push_Top (Interp, X'Unchecked_Access);
+		--Push_Top (Interp, R'Unchecked_Access);
+		R := Make_Cons(Interp.Self, Get_Frame_Result(Interp.Stack), Nil_Pointer);
+		X := Get_Frame_Operand(Interp.Stack);
+
+		pragma Assert (Is_Continuation(X)); -- this procedure can be called for continuation only.
+		Pop_Frame (Interp);
+		Push_Frame_With_Intermediate (Interp, Opcode_Apply, X, R);
+
+		--Pop_Tops (Interp, 2);
+	end Do_Procedure_Call_Finish;
+
 	-- ----------------------------------------------------------------
 
 	procedure Do_Grouped_Call is
@@ -149,7 +183,7 @@ procedure Execute (Interp: in out Interpreter_Record) is
 		pragma Assert (Is_Cons(X)); -- The caller must ensure this.
 		-- Switch the current frame to evaluate the first 
 		-- expression in the group.
-		Switch_Frame (Interp.Stack, Opcode_Evaluate_Object, Get_Car(X));
+		Switch_Frame (Interp.Stack, Opcode_Evaluate_Object, Get_Car(X), Nil_Pointer);
 
 		X := Get_Cdr(X);
 		if Is_Cons(X) then
@@ -333,8 +367,7 @@ print (interp, Get_Frame_Result(Interp.Stack));
 			raise Evaluation_Error;
 		end if;
 
-		Pop_Frame (Interp);     -- Done
-		Put_Frame_Result (Interp, Interp.Stack, Y);
+		Return_Frame (Interp, Y);
 
 		Pop_Tops (Interp, 2);
 	end Do_Set_Finish;
@@ -342,6 +375,8 @@ print (interp, Get_Frame_Result(Interp.Stack));
 	procedure Evaluate is separate;
 	procedure Apply is separate;
 
+	-- --------------------------------------------------------------------
+
 	procedure Unfetch_Character is
 		pragma Inline (Unfetch_Character);
 		pragma Assert (not Interp.LC_Unfetched);	
@@ -672,33 +707,15 @@ Ada.Text_IO.Put_Line ("ERROR: PREMATURE LIST END");
 				Push_Frame (Interp, Opcode_Close_Quote_In_List, Nil_Pointer);
 				Push_Frame (Interp, Opcode_Read_Object, Nil_Pointer);
 
-			when Integer_Token =>
-				-- TODO: bignum
-				V := String_To_Integer_Pointer(Interp.Token.Value.Ptr.all(1..Interp.Token.Value.Last));
-				Chain_Frame_Intermediate (Interp, Interp.Stack, V);
-
-			when Character_Token =>
-				pragma Assert (Interp.Token.Value.Last = 1);
-				V := Character_To_Pointer(Interp.Token.Value.Ptr.all(1));
-				Chain_Frame_Intermediate (Interp, Interp.Stack, V);
-
-			when String_Token =>
-				V := Make_String(Interp.Self, Interp.Token.Value.Ptr.all(1..Interp.Token.Value.Last));
-				Chain_Frame_Intermediate (Interp, Interp.Stack, V);
-
-			when Identifier_Token =>	
-				V := Make_Symbol(Interp.Self, Interp.Token.Value.Ptr.all(1..Interp.Token.Value.Last));
-				Chain_Frame_Intermediate (Interp, Interp.Stack, V);
-
-			when True_Token =>
-				Chain_Frame_Intermediate (Interp, Interp.Stack, True_Pointer);
-
-			when False_Token =>
-				Chain_Frame_Intermediate (Interp, Interp.Stack, False_Pointer);
-
 			when others =>
-				-- TODO: set various error info
-				raise Syntax_Error;
+				V := Token_To_Pointer (Interp.Self, Interp.Token);
+				if V = null then
+					-- TODO: set various error info
+					raise Syntax_Error;
+				else
+					Chain_Frame_Intermediate (Interp, Interp.Stack, V);
+				end if;
+
 		end case;
 
 	end Read_List;
@@ -729,39 +746,16 @@ Ada.Text_IO.Put_Line ("ERROR: CDR QUOT LIST END");
 				Push_Frame (Interp, Opcode_Close_Quote_In_List, Nil_Pointer);
 				Push_Frame (Interp, Opcode_Read_Object, Nil_Pointer);
 
-			when Integer_Token =>
-				-- TODO: bignum
-				V := String_To_Integer_Pointer(Interp.Token.Value.Ptr.all(1..Interp.Token.Value.Last));
-				Set_Frame_Opcode (Interp.Stack, Opcode_Read_List_End);
-				Chain_Frame_Intermediate (Interp, Interp.Stack, V);
-
-			when Character_Token =>
-				pragma Assert (Interp.Token.Value.Last = 1);
-				V := Character_To_Pointer(Interp.Token.Value.Ptr.all(1));
-				Set_Frame_Opcode (Interp.Stack, Opcode_Read_List_End);
-				Chain_Frame_Intermediate (Interp, Interp.Stack, V);
-		
-			when String_Token =>
-				V := Make_String (Interp.Self, Interp.Token.Value.Ptr.all(1..Interp.Token.Value.Last));
-				Set_Frame_Opcode (Interp.Stack, Opcode_Read_List_End);
-				Chain_Frame_Intermediate (Interp, Interp.Stack, V);
-
-			when Identifier_Token =>	
-				V := Make_Symbol (Interp.Self, Interp.Token.Value.Ptr.all(1..Interp.Token.Value.Last));
-				Set_Frame_Opcode (Interp.Stack, Opcode_Read_List_End);
-				Chain_Frame_Intermediate (Interp, Interp.Stack, V);
-
-			when True_Token =>
-				Set_Frame_Opcode (Interp.Stack, Opcode_Read_List_End);
-				Chain_Frame_Intermediate (Interp, Interp.Stack, True_Pointer);
-
-			when False_Token =>
-				Set_Frame_Opcode (Interp.Stack, Opcode_Read_List_End);
-				Chain_Frame_Intermediate (Interp, Interp.Stack, False_Pointer);
-
 			when others =>
-				-- TODO: set various error info
-				raise Syntax_Error;
+				V := Token_To_Pointer (Interp.Self, Interp.Token);
+				if V = null then
+					-- TODO: set various error info
+					raise Syntax_Error;
+				else
+					Chain_Frame_Intermediate (Interp, Interp.Stack, V);
+					Set_Frame_Opcode (Interp.Stack, Opcode_Read_List_End);
+				end if;
+	
 		end case;
 
 	end Read_List_Cdr;
@@ -775,7 +769,7 @@ Ada.Text_IO.Put_Line ("ERROR: CDR QUOT LIST END");
 		case Interp.Token.Kind is
 			when Right_Parenthesis_Token =>
 				V := Get_Frame_Intermediate(Interp.Stack);
-				pragma Assert (V /= Nil_Pointer);
+				pragma Assert (Is_Cons(V));
 				-- The first item in the chain is actually Cdr of the last cell.
 				V := Reverse_Cons(Get_Cdr(V), Get_Car(V)); 
 				Pop_Frame (Interp); 
@@ -792,8 +786,9 @@ Ada.Text_IO.Put_Line ("Right parenthesis expected");
 		V: Object_Pointer;
 	begin
 		V := Get_Frame_Intermediate(Interp.Stack);
-		Pop_Frame (Interp);
-		Set_Frame_Result (Interp.Stack, Get_Car(V));
+		pragma Assert (Is_Cons(V));
+		pragma Assert (Get_Cdr(V) = Nil_Pointer); -- only 1 item as it's used for the top-level list only
+		Return_Frame (Interp, Get_Car(V));
 	end Close_List;
 
 	procedure Close_Quote_In_List is
@@ -814,8 +809,7 @@ Ada.Text_IO.Put_Line ("Right parenthesis expected");
 		V := Get_Frame_Result(Interp.Stack);
 		V := Make_Cons(Interp.Self, V, Nil_Pointer);
 		V := Make_Cons(Interp.Self, Interp.Symbol.Quote, V);
-		Pop_Frame (Interp);
-		Set_Frame_Result (Interp.Stack, V);
+		Return_Frame (Interp, V);
 	end Close_Quote;
 
 	procedure Read_Object is
@@ -837,46 +831,24 @@ Ada.Text_IO.Put_Line ("INFO: NO MORE TOKEN ");
 				Set_Frame_Opcode (Interp.Stack, Opcode_Close_Quote);
 				Push_Frame (Interp, Opcode_Read_Object, Nil_Pointer);
 
-			when Integer_Token =>
-				-- TODO: bignum
-				V := String_To_Integer_Pointer(Interp.Token.Value.Ptr.all(1..Interp.Token.Value.Last));
-				Pop_Frame (Interp); -- Done with the current frame
-				Set_Frame_Result (Interp.Stack, V);
-
-			when Character_Token =>
-				pragma Assert (Interp.Token.Value.Last = 1);
-				V := Character_To_Pointer(Interp.Token.Value.Ptr.all(1));
-				Pop_Frame (Interp); -- Done with the current frame
-				Set_Frame_Result (Interp.Stack, V);
-
-			when String_Token =>
-				V := Make_String (Interp.Self, Interp.Token.Value.Ptr.all(1..Interp.Token.Value.Last));
-				Pop_Frame (Interp); -- Done with the current frame
-				Set_Frame_Result (Interp.Stack, V);
-
-			when Identifier_Token =>	
-				V := Make_Symbol (Interp.Self, Interp.Token.Value.Ptr.all(1..Interp.Token.Value.Last));
-				Pop_Frame (Interp); -- Done with the current frame
-				Set_Frame_Result (Interp.Stack, V);
-
-			when True_Token =>	
-				Pop_Frame (Interp); -- Done with the current frame
-				Set_Frame_Result (Interp.Stack, True_Pointer);
-
-			when False_Token =>	
-				Pop_Frame (Interp); -- Done with the current frame
-				Set_Frame_Result (Interp.Stack, False_Pointer);
-
 			when others =>
-				-- TODO: set various error info
+				V := Token_To_Pointer (Interp.Self, Interp.Token);
+				if V = null then
+					-- TODO: set various error info
 Ada.Text_IO.Put_Line ("INFO: UNKNOWN TOKEN " & Token_Kind'Image(Interp.Token.Kind));
-				raise Syntax_Error;
+					raise Syntax_Error;
+				else
+					Return_Frame (Interp, V);
+				end if;
 		end case;
 
 	end Read_Object;
 
+	-- --------------------------------------------------------------------
+
 begin
 	
+	-- TODO: This comment is out-dated. Update it with Intermediate.
 	-- Stack frames looks like this upon initialization
 	-- 
 	--               | Opcode                 | Operand    | Result
@@ -940,7 +912,7 @@ begin
 	pragma Assert (Interp.Stack /= Nil_Pointer);
 
 	-- The caller must ensure there are no temporary object pointers.
-	pragma Assert (Interp.Top.Last < Interp.Top.Data'First);
+	--pragma Assert (Interp.Top.Last < Interp.Top.Data'First);
 
 	loop
 ada.text_io.put_line (Opcode_Type'Image(Get_Frame_Opcode(Interp.Stack)));
@@ -982,6 +954,8 @@ ada.text_io.put_line (Opcode_Type'Image(Get_Frame_Opcode(Interp.Stack)));
 
 			when Opcode_Procedure_Call =>
 				Do_Procedure_Call;
+			when Opcode_Procedure_Call_Finish =>
+				Do_Procedure_Call_Finish;
 
 			when Opcode_Set_Finish =>
 				Do_Set_Finish; -- Assignment
diff --git a/lib/h2-scheme-token.adb b/lib/h2-scheme-token.adb
index 0979620..7973caf 100644
--- a/lib/h2-scheme-token.adb
+++ b/lib/h2-scheme-token.adb
@@ -130,5 +130,4 @@ package body Token is
 		Append_Buffer (Interp, Interp.Token.Value, Tmp);
 	end Append_Character;
 
-
 end Token;
diff --git a/lib/h2-scheme.adb b/lib/h2-scheme.adb
index 4751504..68eb96f 100644
--- a/lib/h2-scheme.adb
+++ b/lib/h2-scheme.adb
@@ -109,6 +109,7 @@ package body H2.Scheme is
 		Opcode_Let_Evaluation,
 		Opcode_Let_Finish,
 		Opcode_Procedure_Call,
+		Opcode_Procedure_Call_Finish,
 		Opcode_Set_Finish,
 	
 		Opcode_Apply,
@@ -413,6 +414,35 @@ package body H2.Scheme is
 		 return Integer_To_Pointer(Opcode_Type'Pos(Opcode));
 	end Opcode_To_Pointer;
 
+	function Token_To_Pointer (Interp: access Interpreter_Record; 
+	                           Token:  in     Token_Record) return Object_Pointer is
+	begin
+		case Token.Kind is
+			when Integer_Token =>
+				-- TODO: bignum
+				return String_To_Integer_Pointer(Token.Value.Ptr.all(1..Token.Value.Last));
+
+			when Character_Token =>
+				pragma Assert (Token.Value.Last = 1);
+				return Character_To_Pointer(Token.Value.Ptr.all(1));
+		
+			when String_Token =>
+				return Make_String (Interp, Token.Value.Ptr.all(1..Token.Value.Last));
+
+			when Identifier_Token =>	
+				return Make_Symbol (Interp, Token.Value.Ptr.all(1..Token.Value.Last));
+
+			when True_Token =>
+				return True_Pointer;
+
+			when False_Token =>
+				return False_Pointer;
+
+			when others =>
+				return null;
+		end case;
+	end Token_To_Pointer;
+
 	-----------------------------------------------------------------------------
 	-- MEMORY MANAGEMENT
 	-----------------------------------------------------------------------------
@@ -724,6 +754,7 @@ ada.text_io.put_line ("HEAP SOURCE IS NIL");
 
 	begin
 
+Ada.Text_IO.Put_LINE ("GC RUNNING");
 --declare
 --Avail: Heap_Size;
 --begin
@@ -1143,21 +1174,20 @@ Ada.Text_IO.Put_Line ("Make_String...");
 	-----------------------------------------------------------------------------
 
 	function Make_Frame (Interp:  access Interpreter_Record;
-	                     Stack:   in     Object_Pointer; -- current stack pointer
+	                     Parent:   in     Object_Pointer; -- current stack pointer
 	                     Opcode:  in     Object_Pointer;
 	                     Operand: in     Object_Pointer;
 	                     Envir:   in     Object_Pointer;
 	                     Interm:  in     Object_Pointer) return Object_Pointer is
 		Frame: Object_Pointer;
-		Aliased_Stack: aliased Object_Pointer := Stack;
+		Aliased_Parent: aliased Object_Pointer := Parent;
 		Aliased_Opcode: aliased Object_Pointer := Opcode;
 		Aliased_Operand: aliased Object_Pointer := Operand;
 		Aliased_Envir: aliased Object_Pointer := Envir;
 		Aliased_Interm: aliased Object_Pointer := Interm;
 
 	begin
-
-		Push_Top (Interp.all, Aliased_Stack'Unchecked_Access);
+		Push_Top (Interp.all, Aliased_Parent'Unchecked_Access);
 		Push_Top (Interp.all, Aliased_Opcode'Unchecked_Access);
 		Push_Top (Interp.all, Aliased_Operand'Unchecked_Access);
 		Push_Top (Interp.all, Aliased_Envir'Unchecked_Access);
@@ -1167,12 +1197,11 @@ Ada.Text_IO.Put_Line ("Make_String...");
 --       Since it's used for stack, it can be made special.
 		Frame := Allocate_Pointer_Object (Interp, Frame_Object_Size, Nil_Pointer);
 		Frame.Tag := Frame_Object;
-		Frame.Pointer_Slot(Frame_Parent_Index) := Aliased_Stack;
+		Frame.Pointer_Slot(Frame_Parent_Index) := Aliased_Parent;
 		Frame.Pointer_Slot(Frame_Opcode_Index) := Aliased_Opcode;
 		Frame.Pointer_Slot(Frame_Operand_Index) := Aliased_Operand;
 		Frame.Pointer_Slot(Frame_Environment_Index) := Aliased_Envir;
 		Frame.Pointer_Slot(Frame_Intermediate_Index) := Aliased_Interm;
---Print_Object_Pointer ("Make_Frame Result - ", Result);
 
 		Pop_Tops (Interp.all, 5);
 		return Frame;
@@ -1244,15 +1273,6 @@ Ada.Text_IO.Put_Line ("Make_String...");
 		Frame.Pointer_Slot(Frame_Result_Index) := Value;
 	end Set_Frame_Result;
 
-	procedure Put_Frame_Result (Interp: in out Interpreter_Record;
-	                              Frame:  in     Object_Pointer; -- TODO: remove this parameter
-	                              Value:  in     Object_Pointer) is
-		pragma Inline (Put_Frame_Result);
-		pragma Assert (Is_Frame(Frame));
-	begin
-		Interp.Stack.Pointer_Slot(Frame_Result_Index) := Value;
-	end Put_Frame_Result;
-
 	procedure Clear_Frame_Result (Frame: in Object_Pointer) is
 	begin
 		Frame.Pointer_Slot(Frame_Result_Index) := Nil_Pointer;
@@ -1310,14 +1330,23 @@ Ada.Text_IO.Put_Line ("Make_String...");
 		return Frame.Pointer_Slot(Frame_Parent_Index);
 	end Get_Frame_Parent;
 
+	procedure Set_Frame_Parent (Frame: in Object_Pointer;
+	                            Value: in Object_Pointer) is
+		pragma Inline (Set_Frame_Parent);
+		pragma Assert (Is_Frame(Frame));
+	begin
+		Frame.Pointer_Slot(Frame_Parent_Index) := Value;
+	end Set_Frame_Parent;
+
 	procedure Switch_Frame (Frame:   in Object_Pointer;
 	                        Opcode:  in Opcode_Type;
-	                        Operand: in Object_Pointer) is
+	                        Operand: in Object_Pointer;
+	                        Interm:  in Object_Pointer) is
 	begin
 		Set_Frame_Opcode (Frame, Opcode);	
 		Set_Frame_Operand (Frame, Operand);	
+		Set_Frame_Intermediate (Frame, Interm);
 		Set_Frame_Result (Frame, Nil_Pointer);
-		--Set_Frame_Intermediate (Frame, Nil_Pointer);
 	end Switch_Frame;
 
 	-----------------------------------------------------------------------------
@@ -2023,9 +2052,11 @@ Ada.Text_IO.Put_Line ("Make_String...");
 	begin
 
 if DEBUG_GC then
-ADA.TEXT_IO.PUT_LINE ("XXXXXXXXXXXXXXXXXXXXXXXXX NO PROINTING XXXXXXXXXXXXXXXXXXXXXXXxxx");
+Print_Object (Source); -- use a recursive version 
+Ada.Text_IO.New_Line;
 return;
 end if;
+
 		-- TODO: Let Make_Frame use a dedicated stack space that's apart from the heap.
 		--       This way, the stack frame doesn't have to be managed by GC.
 
@@ -2038,69 +2069,68 @@ end if;
 
 		loop
 			case Opcode is
-			when 1 =>
-				if Is_Cons(Operand) then
-					-- push cdr
-					Stack := Make_Frame (Interp.Self, Stack, Integer_To_Pointer(2), Get_Cdr(Operand), Nil_Pointer, Nil_Pointer); -- push cdr
-					Ada.Text_IO.Put ("(");
-					Operand := Get_Car(Operand);
-					Opcode := 1;
-				else
-					Print_Atom (Operand);
-					if Stack = Nil_Pointer then 
-						Opcode := 0; -- stack empty. arrange to exit
-						Operand := True_Pointer; -- return value
+				when 1 =>
+					if Is_Cons(Operand) then
+						-- push cdr
+						Stack := Make_Frame (Interp.Self, Stack, Integer_To_Pointer(2), Get_Cdr(Operand), Nil_Pointer, Nil_Pointer); -- push cdr
+						Ada.Text_IO.Put ("(");
+						Operand := Get_Car(Operand);
+						Opcode := 1;
 					else
-						Opcode := Pointer_To_Integer(Stack.Pointer_Slot(Frame_Opcode_Index));
-						Operand := Stack.Pointer_Slot(Frame_Operand_Index);
-						Stack := Stack.Pointer_Slot(Frame_Parent_Index); -- pop
-					end if;
-				end if;
-
-			when 2 =>
-
-				if Is_Cons(Operand) then
-					-- push cdr
-					Stack := Make_Frame (Interp.Self, Stack, Integer_To_Pointer(2), Get_Cdr(Operand), Nil_Pointer, Nil_Pointer); -- push
-					Ada.Text_IO.Put (" ");
-					Operand := Get_Car(Operand); -- car
-					Opcode := 1;
-				else
-					if Operand /= Nil_Pointer then
-						-- cdr of the last cons cell is not null.
-						Ada.Text_IO.Put (" . ");
 						Print_Atom (Operand);
+						if Stack = Nil_Pointer then 
+							Opcode := 0; -- stack empty. arrange to exit
+							Operand := True_Pointer; -- return value
+						else
+							Opcode := Pointer_To_Integer(Stack.Pointer_Slot(Frame_Opcode_Index));
+							Operand := Stack.Pointer_Slot(Frame_Operand_Index);
+							Stack := Stack.Pointer_Slot(Frame_Parent_Index); -- pop
+						end if;
 					end if;
-					Ada.Text_IO.Put (")");
-
-					if Stack = Nil_Pointer then
-						Opcode := 0; -- stack empty. arrange to exit
+	
+				when 2 =>
+	
+					if Is_Cons(Operand) then
+						-- push cdr
+						Stack := Make_Frame (Interp.Self, Stack, Integer_To_Pointer(2), Get_Cdr(Operand), Nil_Pointer, Nil_Pointer); -- push
+						Ada.Text_IO.Put (" ");
+						Operand := Get_Car(Operand); -- car
+						Opcode := 1;
 					else
-						Opcode := Pointer_To_Integer(Stack.Pointer_Slot(Frame_Opcode_Index));
-						Operand := Stack.Pointer_Slot(Frame_Operand_Index);
-						Stack := Stack.Pointer_Slot(Frame_Parent_Index); -- pop 
+						if Operand /= Nil_Pointer then
+							-- cdr of the last cons cell is not null.
+							Ada.Text_IO.Put (" . ");
+							Print_Atom (Operand);
+						end if;
+						Ada.Text_IO.Put (")");
+	
+						if Stack = Nil_Pointer then
+							Opcode := 0; -- stack empty. arrange to exit
+						else
+							Opcode := Pointer_To_Integer(Stack.Pointer_Slot(Frame_Opcode_Index));
+							Operand := Stack.Pointer_Slot(Frame_Operand_Index);
+							Stack := Stack.Pointer_Slot(Frame_Parent_Index); -- pop 
+						end if;
 					end if;
-				end if;
-
-			when others =>
-				exit;
+	
+				when others =>
+					exit;
 			end case;
 		end loop;
 
-		--Print_Object (Source);
 		Ada.Text_IO.New_Line;
 	end Print;
 
-	procedure Insert_Frame (Interp:  in out Interpreter_Record;
-	                        Parent:  in out Object_Pointer;
-	                        Opcode:  in     Opcode_Type; 
-	                        Operand: in     Object_Pointer;
-	                        Envir:   in     Object_Pointer;
-	                        Interm:  in     Object_Pointer) is
+	function Insert_Frame (Interp:  access Interpreter_Record;
+	                       Parent:  in     Object_Pointer;
+	                       Opcode:  in     Opcode_Type; 
+	                       Operand: in     Object_Pointer;
+	                       Envir:   in     Object_Pointer;
+	                       Interm:  in     Object_Pointer) return Object_Pointer is
 		pragma Inline (Insert_Frame);
 		pragma Assert (Parent = Nil_Pointer or else Is_Frame(Parent));
 	begin
-		Parent := Make_Frame(Interp.Self, Parent, Opcode_To_Pointer(Opcode), Operand, Envir, Interm);
+		return Make_Frame(Interp, Parent, Opcode_To_Pointer(Opcode), Operand, Envir, Interm);
 	end Insert_Frame;
 
 	procedure Push_Frame (Interp:  in out Interpreter_Record;
@@ -2108,9 +2138,7 @@ end if;
 	                      Operand: in     Object_Pointer) is
 		pragma Inline (Push_Frame);
 	begin
-		--Interp.Stack := Make_Frame(Interp.Self, Interp.Stack, Opcode_To_Pointer(Opcode),
-		--                           Operand, Get_Frame_Environment(Interp.Stack));
-		Insert_Frame (Interp, Interp.Stack, Opcode, Operand, Get_Frame_Environment(Interp.Stack), Nil_Pointer);
+		Interp.Stack :=Insert_Frame(Interp.Self, Interp.Stack, Opcode, Operand, Get_Frame_Environment(Interp.Stack), Nil_Pointer);
 	end Push_Frame;
 
 	procedure Push_Frame_With_Environment (Interp:  in out Interpreter_Record;
@@ -2119,19 +2147,26 @@ end if;
 	                                       Envir:   in     Object_Pointer) is
 		pragma Inline (Push_Frame_With_Environment);
 	begin
-		--Interp.Stack := Make_Frame(Interp.Self, Interp.Stack, Opcode_To_Pointer(Opcode),
-		--                           Operand, Envir);
-		Insert_Frame (Interp, Interp.Stack, Opcode, Operand, Envir, Nil_Pointer);
+		Interp.Stack := Insert_Frame(Interp.Self, Interp.Stack, Opcode, Operand, Envir, Nil_Pointer);
 	end Push_Frame_With_Environment;
 
+	procedure Push_Frame_With_Intermediate (Interp:  in out Interpreter_Record;
+	                                        Opcode:  in     Opcode_Type; 
+	                                        Operand: in     Object_Pointer;
+	                                        Interm:  in     Object_Pointer) is
+		pragma Inline (Push_Frame_With_Intermediate);
+	begin
+		-- Place a new frame below the existing top frame.
+		Interp.Stack := Insert_Frame (Interp.Self, Interp.Stack, Opcode, Operand, Get_Frame_Environment(Interp.Stack), Interm);
+	end Push_Frame_With_Intermediate;
+
 	procedure Push_Subframe (Interp:  in out Interpreter_Record;
 	                         Opcode:  in     Opcode_Type; 
 	                         Operand: in     Object_Pointer) is
 		pragma Inline (Push_Subframe);
 	begin
 		-- Place a new frame below the existing top frame.
-		Insert_Frame (Interp, Interp.Stack.Pointer_Slot(Frame_Parent_Index),
-		              Opcode, Operand, Get_Frame_Environment(Interp.Stack), Nil_Pointer);
+		Set_Frame_Parent (Interp.Stack, Insert_Frame(Interp.Self, Get_Frame_Parent(Interp.Stack), Opcode, Operand, Get_Frame_Environment(Interp.Stack), Nil_Pointer));
 	end Push_Subframe;
 
 	procedure Push_Subframe_With_Environment (Interp:  in out Interpreter_Record;
@@ -2141,8 +2176,7 @@ end if;
 		pragma Inline (Push_Subframe_With_Environment);
 	begin
 		-- Place a new frame below the existing top frame.
-		Insert_Frame (Interp, Interp.Stack.Pointer_Slot(Frame_Parent_Index),
-		              Opcode, Operand, Envir, Nil_Pointer);
+		Set_Frame_Parent (Interp.Stack, Insert_Frame(Interp.Self, Get_Frame_Parent(Interp.Stack), Opcode, Operand, Envir, Nil_Pointer));
 	end Push_Subframe_With_Environment;
 
 	procedure Push_Subframe_With_Intermediate (Interp:  in out Interpreter_Record;
@@ -2152,8 +2186,7 @@ end if;
 		pragma Inline (Push_Subframe_With_Intermediate);
 	begin
 		-- Place a new frame below the existing top frame.
-		Insert_Frame (Interp, Interp.Stack.Pointer_Slot(Frame_Parent_Index),
-		              Opcode, Operand, Get_Frame_Environment(Interp.Stack), Interm);
+		Set_Frame_Parent (Interp.Stack, Insert_Frame(Interp.Self, Get_Frame_Parent(Interp.Stack), Opcode, Operand, Get_Frame_Environment(Interp.Stack), Interm));
 	end Push_Subframe_With_Intermediate;
 
 	procedure Pop_Frame (Interp: in out Interpreter_Record) is
@@ -2164,6 +2197,16 @@ end if;
 		Interp.Stack := Interp.Stack.Pointer_Slot(Frame_Parent_Index); -- pop 
 	end Pop_Frame;
 
+	procedure Return_Frame (Interp: in out Interpreter_Record;
+	                        Value:  in     Object_Pointer) is
+		pragma Inline (Return_Frame);
+	begin
+		-- Remove the current frame and return a value 
+		-- to a new active(top) frame.
+		Pop_Frame (Interp);
+		Set_Frame_Result (Interp.Stack, Value);
+	end Return_Frame;
+
 	procedure Execute (Interp: in out Interpreter_Record) is separate;
 
 	procedure Evaluate (Interp: in out Interpreter_Record;
@@ -2193,10 +2236,11 @@ end if;
 	procedure Run_Loop (Interp: in out Interpreter_Record;
 	                    Result: out    Object_Pointer) is
 		-- standard read-eval-print loop
+		Aliased_Result: aliased Object_Pointer;
 	begin
 		pragma Assert (Interp.Base_Input.Stream /= null);
 
---DEBUG_GC := Standard.True;
+DEBUG_GC := Standard.True;
 
 		Result := Nil_Pointer;
 
@@ -2206,6 +2250,7 @@ end if;
 		Interp.Stack := Interp.Root_Frame;
 		Clear_Frame_Result (Interp.Stack);
 
+		Push_Top (Interp, Aliased_Result'Unchecked_Access);
 		loop
 			pragma Assert (Interp.Stack = Interp.Root_Frame);
 			pragma Assert (Get_Frame_Result(Interp.Stack) = Nil_Pointer);
@@ -2218,19 +2263,27 @@ end if;
 			pragma Assert (Interp.Stack = Interp.Root_Frame);
 			pragma Assert (Get_Frame_Opcode(Interp.Stack) = Opcode_Exit);
 
-			-- TODO: this result must be kept at some where that GC dowsn't sweep.
-			Result := Get_Frame_Result(Interp.Stack); 
+			Aliased_Result := Get_Frame_Result(Interp.Stack); 
 			Clear_Frame_Result (Interp.Stack);
 
-Ada.Text_IO.Put ("RESULT>>>>>");
-Print (Interp, Result);
+Ada.Text_IO.Put ("RESULT: ");
+Print (Interp, Aliased_Result);
 Ada.Text_IO.Put_Line (">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LOOP ITERATION XXXXXX CHECKPOINT"); 
 		end loop;
 
+		-- Jump into the exception handler not to repeat the same code here.
+		-- In fact, this part must not be reached since the loop above can't
+		-- be broken.
+		raise Stream_End_Error;
+
 	exception
 		when Stream_End_Error =>
 			-- this is not a real error. this indicates the end of input stream.
 			Ada.Text_IO.Put_LINE ("=== BYE ===");
+			Pop_Tops (Interp, 1);
+			if Aliased_Result /= null then
+				Result := Aliased_Result;
+			end if;
 
 		when X: others =>
 			Ada.TEXT_IO.PUT_LINE ("ERROR ERROR ERROR -> " & Ada.Exceptions.Exception_Name(X));
diff --git a/lib/h2-scheme.ads b/lib/h2-scheme.ads
index 7ffb4d9..8beba4f 100644
--- a/lib/h2-scheme.ads
+++ b/lib/h2-scheme.ads
@@ -431,6 +431,15 @@ package H2.Scheme is
 	procedure Run_Loop (Interp: in out Interpreter_Record;
 	                    Result: out    Object_Pointer);
 
+
+	procedure Collect_Garbage (Interp: in out Interpreter_Record);
+
+     function Make_String (Interp: access  Interpreter_Record;
+                           Source: in      Object_Character_Array) return Object_Pointer;
+
+     function Make_Symbol (Interp: access  Interpreter_Record;
+                           Source: in      Object_Character_Array) return Object_Pointer;
+
 	-- -----------------------------------------------------------------------------
 
 
@@ -534,6 +543,7 @@ private
 		procedure Append_Character (Interp: in out Interpreter_Record;
 		                            Value:  in     Object_Character);
 		pragma Inline (Append_Character);
+
 	end Token;