--- stack/stack.c	2002/02/05 22:28:04	1.32
+++ stack/stack.c	2002/02/05 23:00:42	1.33
@@ -58,6 +58,7 @@
 typedef struct {
   stackitem *head;		/* Head of the stack */
   hashtbl symbols;		/* Hash table of all variable bindings */
+  int err;			/* Error flag */
 } environment;
 
 /* A type for pointers to external functions */
@@ -254,7 +255,7 @@
 }
 
 /* Print newline. */
-extern void nl()
+extern void nl(environment *env)
 {
   printf("\n");
 }
@@ -348,6 +349,7 @@
   return out_item;
 }
 
+/* Recall a value from a symbol, if bound */
 extern void rcl(environment *env)
 {
   value *val;
@@ -362,6 +364,10 @@
     return;
   }
   val=((symbol *)(env->head->item->content.ptr))->val;
+  if(val == NULL){
+    printerr("Unbound variable");
+    return;
+  }
   toss(env);		/* toss the symbol */
   push_val(&(env->head), val); /* Return its bound value */
 }
@@ -638,6 +644,7 @@
     toss(env);
 }
 
+/* List all defined words */
 extern void words(environment *env)
 {
   symbol *temp;