5 files changed, 33 insertions, 15 deletions

diff --git a/Makefile b/Makefile
index 45795d8..25975ab 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-main: main.o parser.o builtin.o model.o eval.o exc.o consts.o types.o
+main: main.o parser.o builtin.o model.o eval.o exc.o consts.o types.o hash.o
 	g++ -o main $^ -pg -lgmp
 
 .cpp.o:
diff --git a/TODO.rst b/TODO.rst
index b403d33..c796c3a 100644
--- a/TODO.rst
+++ b/TODO.rst
@@ -1,7 +1,6 @@
-- OPT:Special Opt Repr 
-- OPT:Special Arg Checking
-- Garbage Collection
+- OPT:Special Arg Checking (Again)
 - Testing
+- Garbage Collection
 - Rounding support
 - ext_repr optimization 
 - Add macro support
diff --git a/robust_test.scm b/robust_test.scm
index 6dd4abf..4b68c4e 100644
--- a/robust_test.scm
+++ b/robust_test.scm
@@ -229,3 +229,24 @@ src
 (list x)
 x
 (cons x  x)
+
+(define (f x)
+  (if (<= x 2) 1 (+ (f (- x 1)) (f (- x 2)))))
+(f 1)
+(f 2)
+(f 3)
+(f 4)
+(f 5)
+
+(define (g n)
+  (define (f p1 p2 n)
+    (if (<= n 2)
+      p2
+      (f p2 (+ p1 p2) (- n 1))))
+  (f 1 1 n))
+
+(define (all i n)
+  (if (= n i)
+    #f
+    (and (display (g i)) (all (+ i 1) n))))
+(all 1 100)
diff --git a/types.cpp b/types.cpp
index 8611cc6..031a215 100644
--- a/types.cpp
+++ b/types.cpp
@@ -2,6 +2,7 @@
 #include "model.h"
 #include "exc.h"
 #include "consts.h"
+#include "hash.h"
 
 #include <cmath>
 #include <cstdlib>
@@ -12,6 +13,7 @@ const double EPS = 1e-16;
 const int PREC = 16;
 
 EmptyList *empty_list = new EmptyList();
+static VariableHash var_hash;
 
 Pair::Pair(EvalObj *_car, EvalObj *_cdr) :
     EvalObj(CLS_PAIR_OBJ), car(_car), cdr(_cdr),
@@ -219,20 +221,16 @@ bool Environment::add_binding(SymObj *sym_obj, EvalObj *eval_obj, bool def) {
     if (!def)
     {
         for (Environment *ptr = this; ptr; ptr = ptr->prev_envt)
-        {
-            bool has_key = ptr->binding.count(name);
-            if (has_key) 
+            if (var_hash.insert(ptr, name, eval_obj, false))
             {
-                ptr->binding[name] = eval_obj;
                 found = true;
                 break;
             }
-        }
         return found;
     }
     else 
     {
-        binding[name] = eval_obj;
+        var_hash.insert(this, name, eval_obj);
         return true;
     }
 }
@@ -244,8 +242,8 @@ EvalObj *Environment::get_obj(EvalObj *obj) {
     string name(sym_obj->val);
     for (Environment *ptr = this; ptr; ptr = ptr->prev_envt)
     {
-        bool has_key = ptr->binding.count(name);
-        if (has_key) return ptr->binding[name];
+        EvalObj *obj = var_hash.get(ptr, name);
+        if (obj) return obj;
     }
     // Object not found
     throw TokenError(name, RUN_ERR_UNBOUND_VAR);
diff --git a/types.h b/types.h
index 11776ab..855cfb6 100644
--- a/types.h
+++ b/types.h
@@ -32,7 +32,7 @@ static const int NUM_LVL_INT = 3;
 
 typedef set<EvalObj*> EvalObjAddrHash;
 typedef vector<EvalObj*> EvalObjVec;
-typedef map<string, EvalObj*> Str2EvalObj;
+//typedef map<string, EvalObj*> Str2EvalObj;
 typedef EvalObj* (*BuiltinProc)(Pair *, const string &);
 
 class PairReprCons;
@@ -326,8 +326,8 @@ class PromObj: public EvalObj {/*{{{*/
 class Environment {/*{{{*/
     private:
         Environment *prev_envt; /**< Pointer to the upper-level environment */
-        Str2EvalObj binding;    /**< Store all pairs of identifier and its
-                                  corresponding obj */
+//        Str2EvalObj binding;    /**< Store all pairs of identifier and its
+//                                  corresponding obj */
     public:
         /** Create an runtime environment
          * @param prev_envt the outer environment