--- stack/stack.c	2002/02/05 23:00:42	1.33
+++ stack/stack.c	2002/02/06 00:30:14	1.35
@@ -18,8 +18,6 @@
   enum {
     integer,
     string,
-    ref,			/* Reference (to an element in the
-                                   hash table) */
     func,			/* Function pointer */
     symb, 
     list
@@ -70,6 +68,7 @@
 {
   long i;
 
+  env->err=0;
   for(i= 0; i<HASHTBLSIZE; i++)
     env->symbols[i]= NULL;
 }
@@ -104,11 +103,10 @@
 }
 
 /* Generic push function. */
-int push(stackitem** stack_head, stackitem* in_item)
+void push(stackitem** stack_head, stackitem* in_item)
 {
   in_item->next= *stack_head;
   *stack_head= in_item;
-  return 1;
 }
 
 /* Push a value onto the stack */
@@ -121,7 +119,7 @@
 }
 
 /* Push an integer onto the stack. */
-int push_int(stackitem **stack_head, int in_val) 
+void push_int(stackitem **stack_head, int in_val) 
 {
   value *new_value= malloc(sizeof(value));
   stackitem *new_item= malloc(sizeof(stackitem));
@@ -132,11 +130,10 @@
   new_value->refcount=1;
 
   push(stack_head, new_item);
-  return 1;
 }
 
 /* Copy a string onto the stack. */
-int push_cstring(stackitem **stack_head, const char *in_string)
+void push_cstring(stackitem **stack_head, const char *in_string)
 {
   value *new_value= malloc(sizeof(value));
   stackitem *new_item= malloc(sizeof(stackitem));
@@ -148,11 +145,10 @@
   new_value->refcount=1;
 
   push(stack_head, new_item);
-  return 1;
 }
 
 /* Push a symbol onto the stack. */
-int push_sym(environment *env, const char *in_string)
+void push_sym(environment *env, const char *in_string)
 {
   stackitem *new_item;		/* The new stack item */
   /* ...which will contain... */
@@ -207,7 +203,6 @@
     }
   }
   push(&(env->head), new_item);
-  return 1;
 }
 
 void printerr(const char* in_string) {
@@ -246,6 +241,7 @@
 
   if((env->head)==NULL) {
     printerr("Stack empty");
+    env->err=1;
     return;
   }
   
@@ -255,7 +251,7 @@
 }
 
 /* Print newline. */
-extern void nl(environment *env)
+extern void nl()
 {
   printf("\n");
 }
@@ -263,12 +259,6 @@
 /* Prints the top element of the stack. */
 void print_h(stackitem *stack_head)
 {
-
-  if(stack_head==NULL) {
-    printerr("Stack empty");
-    return;
-  }
-
   switch(stack_head->item->type) {
   case integer:
     printf("%d", stack_head->item->content.val);
@@ -279,13 +269,24 @@
   case symb:
     printf("'%s'", ((symbol *)(stack_head->item->content.ptr))->id);
     break;
+  case func:
+    printf("#<function %p>", (funcp)(stack_head->item->content.ptr));
+    break;
+  case list:
+    printf("#<list %p>", (funcp)(stack_head->item->content.ptr));
+    break;
   default:
-    printf("%p", (funcp)(stack_head->item->content.ptr));
+    printf("#<unknown %p>", (funcp)(stack_head->item->content.ptr));
     break;
   }
 }
 
 extern void print_(environment *env) {
+  if(env->head==NULL) {
+    printerr("Stack empty");
+    env->err=1;
+    return;
+  }
   print_h(env->head);
 }
 
@@ -293,6 +294,7 @@
 extern void print(environment *env)
 {
   print_(env);
+  if(env->err) return;
   toss(env);
 }
 
@@ -311,12 +313,13 @@
 /* Prints the stack. */
 extern void printstack(environment *env)
 {
-  if(env->head != NULL) {
-    print_st(env->head, 1);
-    nl();
-  } else {
+  if(env->head == NULL) {
     printerr("Stack empty");
+    env->err=1;
+    return;
   }
+  print_st(env->head, 1);
+  nl();
 }
 
 /* Swap the two top elements on the stack. */
@@ -326,11 +329,13 @@
   
   if((env->head)==NULL) {
     printerr("Stack empty");
+    env->err=1;
     return;
   }
 
   if(env->head->next==NULL) {
     printerr("Not enough arguments");
+    env->err=1;
     return;
   }
 
@@ -356,19 +361,24 @@
 
   if(env->head == NULL) {
     printerr("Stack empty");
+    env->err=1;
     return;
   }
 
   if(env->head->item->type!=symb) {
     printerr("Not a symbol");
+    env->err=1;
     return;
   }
+
   val=((symbol *)(env->head->item->content.ptr))->val;
   if(val == NULL){
     printerr("Unbound variable");
+    env->err=1;
     return;
   }
   toss(env);		/* toss the symbol */
+  if(env->err) return;
   push_val(&(env->head), val); /* Return its bound value */
 }
 
@@ -378,43 +388,30 @@
 extern void eval(environment *env)
 {
   funcp in_func;
-  value* val;
   if(env->head==NULL) {
     printerr("Stack empty");
+    env->err=1;
     return;
   }
 
   /* if it's a symbol */
   if(env->head->item->type==symb) {
 
-    /* If it's not bound to anything */
-    if (((symbol *)(env->head->item->content.ptr))->val == NULL) {
-      printerr("Unbound variable");
+    rcl(env);			/* get its contents */
+    if(env->err) return;
+    if(env->head->item->type!=symb){ /* don't recurse symbols */
+      eval(env);			/* evaluate the value */
       return;
     }
-    
-    /* If it contains a function */
-    if (((symbol *)(env->head->item->content.ptr))->val->type == func) {
-      in_func=
-	(funcp)(((symbol *)(env->head->item->content.ptr))->val->content.ptr);
-      toss(env);
-      (*in_func)(env);		/* Run the function */
-      return;
-    } else {			/* If it's not a function */
-      val=((symbol *)(env->head->item->content.ptr))->val;
-      toss(env);		/* toss the symbol */
-      push_val(&(env->head), val); /* Return its bound value */
-    }
   }
 
   /* If it's a lone function value, run it */
   if(env->head->item->type==func) {
     in_func= (funcp)(env->head->item->content.ptr);
     toss(env); 
+    if(env->err) return;
     (*in_func)(env);
-    return;
   }
-
 }
 
 /* Make a list. */
@@ -489,7 +486,7 @@
       break;
     } 
     /* If symbol */
-    if((convert= sscanf(in_line, "%[^][ ;\n\r_]%[^\n\r]", temp, rest))) {
+    if((convert= sscanf(in_line, "%[^][ ;\n\r]%[^\n\r]", temp, rest))) {
 	push_sym(env, temp);
 	break;
     }
@@ -543,6 +540,7 @@
   /* Is top element a list? */
   if(env->head==NULL || env->head->item->type!=list) {
     printerr("Stack empty or not a list");
+    env->err=1;
     return;
   }
 
@@ -570,6 +568,7 @@
 
   if((env->head)==NULL || env->head->next==NULL) {
     printerr("Not enough elements to compare");
+    env->err=1;
     return;
   }
 
@@ -589,6 +588,7 @@
 
   if((env->head)==NULL || env->head->item->type!=integer) {
     printerr("Stack empty or element is not a integer");
+    env->err=1;
     return;
   }
 
@@ -614,6 +614,7 @@
   if(env->head==NULL || env->head->next==NULL 
      || env->head->item->type!=symb) {
     printerr("Define what?");
+    env->err=1;
     return;
   }
 
@@ -659,6 +660,32 @@
   }
 }
 
+/* Forgets a symbol (remove it from the hash table) */
+extern void forget(environment *env)
+{
+  char* sym_id;
+  stackitem *stack_head= env->head;
+  symbol **hash_entry, *temp;
+
+  if(stack_head==NULL || stack_head->item->type!=symb) {
+    printerr("Stack empty or not a symbol");
+    return;
+  }
+
+  sym_id= ((symbol*)(stack_head->item->content.ptr))->id;
+  toss(env);
+
+  hash_entry= hash(env->symbols, sym_id);
+  temp= *hash_entry;
+  *hash_entry= (*hash_entry)->next;
+  
+  if(temp->val!=NULL) {
+    free_val(temp->val);
+  }
+  free(temp->id);
+  free(temp);
+} 
+
 int main()
 {
   environment myenv;
@@ -670,6 +697,10 @@
 
   while(fgets(in_string, 100, stdin) != NULL) {
     stack_read(&myenv, in_string);
+    if(myenv.err) {
+      printf("(error %d) ", myenv.err);
+      myenv.err=0;
+    }
     printf("okidok\n ");
   }