4 files changed, 24 insertions, 9 deletions

diff --git a/eval.cpp b/eval.cpp
index 0b9150e..6376ba9 100644
--- a/eval.cpp
+++ b/eval.cpp
@@ -102,7 +102,7 @@ void push(Pair * &pc, FrameObj ** &top_ptr, Environment *envt) {
             throw NormalError(SYN_ERR_EMPTY_COMB);
 
         *top_ptr++ = new RetAddr(pc);       // Push the return address
-        if (!is_list(TO_PAIR(pc->car)))
+        if (!make_exec(TO_PAIR(pc->car)))
             throw TokenError(pc->car->ext_repr(), RUN_ERR_WRONG_NUM_OF_ARGS);
         // static_cast because of is_simple_obj() is false
         pc = static_cast<Pair*>(pc->car);  // Go deeper to enter the call
@@ -121,7 +121,6 @@ EvalObj *Evaluator::run_expr(Pair *prog) {
     {
         if (top_ptr == eval_stack + EVAL_STACK_SIZE)
             throw TokenError("Evaluation", RUN_ERR_STACK_OVERFLOW);
-//        for (; pc && pc->skip; pc = pc->next);
         if (pc)
             push(pc, top_ptr, envt);
         else
diff --git a/model.cpp b/model.cpp
index 85d4e04..564aa74 100644
--- a/model.cpp
+++ b/model.cpp
@@ -84,8 +84,13 @@ string EvalObj::ext_repr() {
             if (obj)
             {
                 *(++top_ptr) = obj->get_repr_cons();
-                if (hash.count((*top_ptr)->ori))
-                    *top_ptr = new ReprStr("#inf#");
+                EvalObj *ptr = (*top_ptr)->ori;
+                if (ptr)
+                {
+                    if (hash.count(ptr))
+                        *top_ptr = new ReprStr("#inf#");
+                    else hash.insert(ptr);
+                }
             }
             else
             {
@@ -100,8 +105,13 @@ string EvalObj::ext_repr() {
             if (obj)
             {
                 *(++top_ptr) = obj->get_repr_cons();
-                if (hash.count((*top_ptr)->ori))
-                    *top_ptr = new ReprStr("#inf#");
+                EvalObj *ptr = (*top_ptr)->ori;
+                if (ptr)
+                {
+                    if (hash.count(ptr))
+                        *top_ptr = new ReprStr("#inf#");
+                    else hash.insert(ptr);
+                }
             }
             else *top_ptr = new ReprStr((*top_ptr)->repr);
         }
@@ -401,13 +411,17 @@ EvalObj *PromObj::get_mem() { return mem; }
 void PromObj::feed_mem(EvalObj *res) { mem = res; }
 
 
-bool is_list(Pair *ptr) {
+bool make_exec(Pair *ptr) {
     if (ptr == empty_list) return true;
     EvalObj *nptr;
     for (;;)
         if ((nptr = ptr->cdr)->is_pair_obj())
-            ptr = TO_PAIR(nptr);
+        {
+            ptr->next = TO_PAIR(nptr);
+            ptr = ptr->next;
+        }
         else break;
+    ptr->next = NULL;
     return ptr->cdr == empty_list;
 }
 
diff --git a/model.h b/model.h
index 58f45f4..955e2b4 100644
--- a/model.h
+++ b/model.h
@@ -464,6 +464,6 @@ class Continuation {
                 Pair *proc_body);
 };
 
-bool is_list(Pair *ptr);
+bool make_exec(Pair *ptr);
 
 #endif
diff --git a/robust_test.scm b/robust_test.scm
index 152e380..bc327ea 100644
--- a/robust_test.scm
+++ b/robust_test.scm
@@ -172,6 +172,8 @@ t
 src
 (eval src)
 (eval '(g 0))
+(eval (list * 2 3))
+(eval '(* 2 3))
 
 (define f (lambda (x) (+ x x))) ;; test comments
 ((lambda (x y) (f 3)) 1 2)      ;; first-class procedure