diff --git a/assignments/PA5/cgen.cc b/assignments/PA5/cgen.cc
index 36887e0..5046abf 100644
--- a/assignments/PA5/cgen.cc
+++ b/assignments/PA5/cgen.cc
@@ -93,6 +93,7 @@ static char *gc_collect_names[] = {"_NoGC_Collect", "_GenGC_Collect",
 BoolConst falsebool(FALSE);
 BoolConst truebool(TRUE);
 
+static int rel_stack_depth;
 //*********************************************************
 //
 // Define method for code generation
@@ -297,6 +298,17 @@ static void emit_branch(int l, ostream &s) {
 static void emit_push(char *reg, ostream &str) {
   emit_store(reg, 0, SP, str);
   emit_addiu(SP, SP, -4, str);
+  rel_stack_depth++;
+}
+
+static void emit_pop(ostream &str) {
+  emit_addiu(SP, SP, 4, str);
+  rel_stack_depth--;
+}
+
+static void emit_pop(size_t count, ostream &str) {
+  emit_addiu(SP, SP, 4 * count, str);
+  rel_stack_depth -= count;
 }
 
 //
@@ -674,13 +686,13 @@ void CgenClassTable::install_basic_classes() {
   //
   addid(No_class,
         new CgenNode(class_(No_class, No_class, nil_Features(), filename),
-                     Basic, this));
+                     Trivial));
   addid(SELF_TYPE,
         new CgenNode(class_(SELF_TYPE, No_class, nil_Features(), filename),
-                     Basic, this));
+                     Trivial));
   addid(prim_slot,
         new CgenNode(class_(prim_slot, No_class, nil_Features(), filename),
-                     Basic, this));
+                     Trivial));
 
   //
   // The Object class has no parent class. Its methods are
@@ -702,7 +714,7 @@ void CgenClassTable::install_basic_classes() {
               single_Features(
                   method(copy, nil_Formals(), SELF_TYPE, no_expr()))),
           filename),
-      Basic, this));
+      Basic));
 
   //
   // The IO class inherits from Object. Its methods are
@@ -727,7 +739,7 @@ void CgenClassTable::install_basic_classes() {
                       method(in_string, nil_Formals(), Str, no_expr()))),
               single_Features(method(in_int, nil_Formals(), Int, no_expr()))),
           filename),
-      Basic, this));
+      Basic));
 
   //
   // The Int class has no methods and only a single attribute, the
@@ -736,7 +748,7 @@ void CgenClassTable::install_basic_classes() {
   install_class(new CgenNode(
       class_(Int, Object, single_Features(attr(val, prim_slot, no_expr())),
              filename),
-      Basic, this));
+      Basic));
 
   //
   // Bool also has only the "val" slot.
@@ -744,7 +756,7 @@ void CgenClassTable::install_basic_classes() {
   install_class(new CgenNode(
       class_(Bool, Object, single_Features(attr(val, prim_slot, no_expr())),
              filename),
-      Basic, this));
+      Basic));
 
   //
   // The class Str has a number of slots and operations:
@@ -774,7 +786,7 @@ void CgenClassTable::install_basic_classes() {
                                            single_Formals(formal(arg2, Int))),
                             Str, no_expr()))),
              filename),
-      Basic, this));
+      Basic));
 
   stringclasstag = get_node(Str)->get_class_tag();
   intclasstag = get_node(Int)->get_class_tag();
@@ -802,7 +814,7 @@ void CgenClassTable::install_class(CgenNodeP nd) {
 
 void CgenClassTable::install_classes(Classes cs) {
   for (int i = cs->first(); cs->more(i); i = cs->next(i))
-    install_class(new CgenNode(cs->nth(i), NotBasic, this));
+    install_class(new CgenNode(cs->nth(i), NotBasic));
 }
 
 //
@@ -825,6 +837,127 @@ void CgenClassTable::set_relations(CgenNodeP nd) {
   parent_node->add_child(nd);
 }
 
+void CgenClassTable::dump_inheritance_tree() {
+  CgenNode *object_node = nullptr;
+
+  for (auto cur_node : nodes) {
+    if (cur_node->name == Object) {
+      object_node = cur_node;
+      break;
+    }
+  }
+  object_node->traverse_dump(0);
+}
+
+CgenNode *CgenClassTable::get_node(Symbol class_name) {
+  for (auto node : nodes) {
+    if (node->name == class_name) {
+      return node;
+    }
+  }
+  if (cgen_debug)
+    std::cerr << "get_node " << class_name << " not found\n";
+  assert(0);
+  return nullptr;
+}
+
+void CgenClassTable::code() {
+  if (cgen_debug)
+    cout << "coding global data" << endl;
+  code_global_data();
+
+  if (cgen_debug)
+    cout << "choosing gc" << endl;
+  code_select_gc();
+
+  if (cgen_debug)
+    cout << "coding constants" << endl;
+  code_constants();
+
+  if (cgen_debug)
+    cout << "coding class_nameTab" << endl;
+  code_class_nameTable();
+
+  if (cgen_debug)
+    cout << "coding dispatch tables" << endl;
+  nodes[0]->traverse_generate_object();
+  // nodes[0] is the Object class
+  code_dispatchTable();
+
+  if (cgen_debug)
+    cout << "coding prototype objects" << endl;
+  code_prototypeObject();
+
+  if (cgen_debug)
+    cout << "coding global text" << endl;
+  code_global_text();
+
+#if 0
+// test my symtab impl
+  for (auto node : nodes) {
+    auto attrs = *node->get_attributes();
+    auto methods = *node->get_methods();
+    std::cerr << node->name << std::endl;
+    loctab.enterscope();
+    for (size_t i = 0; i < attrs.size(); ++ i) {
+      auto attr = attrs[i];
+      loctab.add(LocationTableItem(attr->name, Attribute, i));
+    }
+    loctab.enterscope();
+    for (size_t i = 0; i < methods.size(); ++ i) {
+      auto method = methods[i];
+      loctab.add(LocationTableItem(method.second->name, Attribute, i));
+    }
+    loctab.enterscope();
+    for (size_t i = 0; i < attrs.size(); ++ i) {
+      auto attr = attrs[i];
+      loctab.add(LocationTableItem(attr->name, Attribute, i + 10000));
+    }
+    // loctab.dump();
+    for (size_t i = 0; i < attrs.size(); ++ i) {
+      auto attr = attrs[i];
+      assert(loctab.lookup(attr->name));
+      assert(loctab.lookup(attr->name)->offset == i + 10000);
+    }
+    loctab.exitscope();
+    for (size_t i = 0; i < attrs.size(); ++ i) {
+      auto attr = attrs[i];
+      assert(loctab.lookup(attr->name) && loctab.lookup(attr->name)->offset == i);
+    }
+      loctab.exitscope();
+    for (size_t i = 0; i < attrs.size(); ++ i) {
+      auto attr = attrs[i];
+      assert(loctab.lookup(attr->name) && loctab.lookup(attr->name)->offset == i);
+    }
+    loctab.exitscope();
+    for (size_t i = 0; i < attrs.size(); ++ i) {
+      auto attr = attrs[i];
+      assert(loctab.lookup(attr->name) == nullptr);
+    }
+  }
+#endif
+  //                 Add your code to emit
+  //                   - object initializer
+  //                   - the class methods
+  //                   - etc...
+}
+
+///////////////////////////////////////////////////////////////////////
+//
+// CgenNode methods
+//
+///////////////////////////////////////////////////////////////////////
+
+#pragma region CgenNode
+
+CgenNode::CgenNode(Class_ nd, Basicness bstatus)
+    : class__class((const class__class &)*nd), parentnd(NULL),
+      basic_status(bstatus) {
+  if (!(bstatus == Trivial))
+    stringtable.add_string(
+        name->get_string()); // Add class name to string table
+}
+
 void CgenNode::add_child(CgenNodeP n) { children.push_back(n); }
 
 void CgenNode::set_parentnd(CgenNodeP p) {
@@ -898,80 +1031,7 @@ void CgenNode::traverse_generate_object() {
   }
 }
 
-void CgenClassTable::dump_inheritance_tree() {
-  CgenNode *object_node = nullptr;
-
-  for (auto cur_node : nodes) {
-    if (cur_node->name == Object) {
-      object_node = cur_node;
-      break;
-    }
-  }
-  object_node->traverse_dump(0);
-}
-
-CgenNode *CgenClassTable::get_node(Symbol class_name) {
-  for (auto node : nodes) {
-    if (node->name == class_name) {
-      return node;
-    }
-  }
-  if (cgen_debug)
-    std::cerr << "get_node " << class_name << " not found\n";
-  assert(0);
-  return nullptr;
-}
-
-void CgenClassTable::code() {
-  if (cgen_debug)
-    cout << "coding global data" << endl;
-  code_global_data();
-
-  if (cgen_debug)
-    cout << "choosing gc" << endl;
-  code_select_gc();
-
-  if (cgen_debug)
-    cout << "coding constants" << endl;
-  code_constants();
-
-  if (cgen_debug)
-    cout << "coding class_nameTab" << endl;
-  code_class_nameTable();
-
-  if (cgen_debug)
-    cout << "coding dispatch tables" << endl;
-  nodes[0]->traverse_generate_object();
-  // nodes[0] is the Object class
-  code_dispatchTable();
-
-  if (cgen_debug)
-    cout << "coding prototype objects" << endl;
-  code_prototypeObject();
-
-  if (cgen_debug)
-    cout << "coding global text" << endl;
-  code_global_text();
-
-  //                 Add your code to emit
-  //                   - object initializer
-  //                   - the class methods
-  //                   - etc...
-}
-
-CgenNodeP CgenClassTable::root() { return probe(Object); }
-
-///////////////////////////////////////////////////////////////////////
-//
-// CgenNode methods
-//
-///////////////////////////////////////////////////////////////////////
-
-CgenNode::CgenNode(Class_ nd, Basicness bstatus, CgenClassTableP ct)
-    : class__class((const class__class &)*nd), parentnd(NULL),
-      basic_status(bstatus) {
-  stringtable.add_string(name->get_string()); // Add class name to string table
-}
+#pragma endregion
 
 //******************************************************************
 //
@@ -1041,7 +1101,11 @@ void block_class::code(ostream &s, CgenClassTable *classtab) {
   }
 }
 
-void let_class::code(ostream &s, CgenClassTable *classtab) {}
+void let_class::code(ostream &s, CgenClassTable *classtab) {
+  this->init->code(s, classtab);
+  emit_push(ZERO, s); // make space for let's new object
+  
+}
 
 /*
   Operations for Int objects is the most simple one, let's start here
@@ -1073,7 +1137,7 @@ void plus_class::code(ostream &s, CgenClassTable *classtab) {
   emit_add(T1, T1, ACC, s);   // $t1 <- val(e1) + val(e2)
   emit_load(ACC, 1, SP, s);   // load new object addr
   emit_store_int(T1, ACC, s); // store result(now in $t1) to the object
-  emit_addiu(SP, SP, 8, s);   // maintain stack balance
+  emit_pop(2, s);             // maintain stack balance
 }
 
 /*
@@ -1092,7 +1156,7 @@ void sub_class::code(ostream &s, CgenClassTable *classtab) {
   emit_sub(T1, T1, ACC, s);    // $t1 <- val(e1),$t1 + val(e2),$a0
   emit_load(ACC, 1, SP, s);
   emit_store_int(T1, ACC, s);
-  emit_addiu(SP, SP, 8, s);
+  emit_pop(2, s);
 }
 
 /*
@@ -1111,7 +1175,7 @@ void mul_class::code(ostream &s, CgenClassTable *classtab) {
   emit_mul(T1, T1, ACC, s);    // $t1 <- val(e1),$t1 + val(e2),$a0
   emit_load(ACC, 1, SP, s);
   emit_store_int(T1, ACC, s);
-  emit_addiu(SP, SP, 8, s);
+  emit_pop(2, s);
 }
 
 void divide_class::code(ostream &s, CgenClassTable *classtab) {
@@ -1126,7 +1190,7 @@ void divide_class::code(ostream &s, CgenClassTable *classtab) {
   emit_div(T1, T1, ACC, s);    // $t1 <- val(e1),$t1 + val(e2),$a0
   emit_load(ACC, 1, SP, s);
   emit_store_int(T1, ACC, s);
-  emit_addiu(SP, SP, 8, s);
+  emit_pop(2, s);
 }
 
 /*
@@ -1179,7 +1243,7 @@ void lt_class::code(ostream &s, CgenClassTable *classtab) {
   emit_label_def(label_index_true, s); // first branch goes to here
   emit_load_bool(ACC, truebool, s);    // branch means true
   emit_label_def(label_index_exit, s); // second jump goes to here
-  emit_addiu(SP, SP, 4, s);            // cleanup anyway, only one push is made
+  emit_pop(1, s);                      // cleanup anyway, only one push is made
 }
 
 /*
@@ -1200,7 +1264,7 @@ void leq_class::code(ostream &s, CgenClassTable *classtab) {
   emit_label_def(label_index_true, s);
   emit_load_bool(ACC, truebool, s);
   emit_label_def(label_index_exit, s);
-  emit_addiu(SP, SP, 4, s);
+  emit_pop(1, s);
 }
 
 /*
@@ -1250,7 +1314,7 @@ void eq_class::code(ostream &s, CgenClassTable *classtab) {
   // at this point, $t1=&e1, $t2=&e2, $a0=true, $a1=false. ready to call
   // $a0 will be either true or false, so just keep it as the result
   emit_label_def(label_index_exit, s);
-  emit_addiu(SP, SP, 4, s); // balance stack, 1 push in this expression
+  emit_pop(1, s); // balance stack, 1 push in this expression
 }
 
 void int_const_class::code(ostream &s, CgenClassTable *classtab) {
diff --git a/assignments/PA5/cgen.h b/assignments/PA5/cgen.h
index 4f71f27..6ef275e 100644
--- a/assignments/PA5/cgen.h
+++ b/assignments/PA5/cgen.h
@@ -9,7 +9,9 @@
 #include <utility>
 #include <vector>
 
-enum Basicness { Basic, NotBasic };
+enum Basicness { Basic, NotBasic, Trivial };
+enum VariableLocation { Attribute, Stack };
+
 #define TRUE 1
 #define FALSE 0
 
@@ -22,6 +24,51 @@ typedef CgenNode *CgenNodeP;
 typedef std::vector<std::pair<class__class *, method_class *>> MethodListT;
 typedef std::vector<attr_class *> AttrListT;
 
+struct LocationTableItem {
+  LocationTableItem(Symbol id, VariableLocation loc, int off)
+      : id(id), location(loc), offset(off) {}
+  Symbol id;
+  VariableLocation location;
+  int offset;
+};
+
+class LocationTable {
+private:
+  std::vector<LocationTableItem> table;
+  std::vector<size_t> scope;
+public:
+  // lookup the inner-most item with the same id as name
+  LocationTableItem* lookup(Symbol name) {
+    for (auto itr = table.rbegin(); itr != table.rend(); ++ itr) {
+      if (itr->id == name) {
+        return &*itr;
+      }
+    }
+    return nullptr;
+  }
+  void add(LocationTableItem item) {
+    table.push_back(item);
+  };
+  void enterscope() {
+    scope.push_back(table.size());
+  }
+  void exitscope() {
+    auto end = scope.back();
+    scope.pop_back();
+    table.erase(table.begin() + end, table.end());
+  }
+  void dump() {
+    scope.push_back(table.size());
+    for (size_t i = 0; i < scope.size() - 1; ++ i) {
+      std::cerr << "scope" << i << "\n";
+      for (size_t j = scope[i]; j < scope[i+1]; j ++) {
+        std::cerr << table[j].id << ", " << table[j].location << ", " << table[j].offset << "\n";
+      }
+    }
+    scope.pop_back();
+  }
+};
+
 class CgenClassTable : public SymbolTable<Symbol, CgenNode> {
 private:
   std::vector<CgenNode *> nodes;
@@ -59,9 +106,10 @@ private:
   void gen_init_code();
 
 public:
+  LocationTable loctab;
   CgenClassTable(Classes, ostream &str);
   void code();
-  CgenNodeP root();
+  CgenNode* root() { return nodes[0]; }
   /* aquire an unused label index */
   int alloc_label_index() { return label_count++; }
 };
@@ -82,7 +130,7 @@ private:
   // method list including inherited and overidden methods
 
 public:
-  CgenNode(Class_ c, Basicness bstatus, CgenClassTableP class_table);
+  CgenNode(Class_ c, Basicness bstatus);
 
   void add_child(CgenNodeP child);
   std::vector<CgenNode *> *get_children() { return &children; }
diff --git a/assignments/PA5/example.cl b/assignments/PA5/example.cl
index fbf83ba..84d148e 100644
--- a/assignments/PA5/example.cl
+++ b/assignments/PA5/example.cl
@@ -71,6 +71,14 @@ class E {
   method_isvoid(x1: Object) : Bool {
     isvoid x1
   };
+  method_let1(x1: Int) : Object {
+    let x2 : Int <- x1 + 10 in
+      x2 <- x1
+  };
+  method_let2(x1: Int) : Object {
+    let x2 : Int <- x1 in
+      x2 <- x1 + 100
+  };
 };
 
 class Main inherits IO {