--- stack/stack.c	2002/02/04 21:47:26	1.28
+++ stack/stack.c	2002/02/05 23:26:46	1.34
@@ -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 */
@@ -110,8 +111,17 @@
   return 1;
 }
 
+/* Push a value onto the stack */
+void push_val(stackitem **stack_head, value *val)
+{
+  stackitem *new_item= malloc(sizeof(stackitem));
+  new_item->item= val;
+  val->refcount++;
+  push(stack_head, new_item);
+}
+
 /* Push an integer onto the stack. */
-int push_val(stackitem **stack_head, int in_val) 
+int push_int(stackitem **stack_head, int in_val) 
 {
   value *new_value= malloc(sizeof(value));
   stackitem *new_item= malloc(sizeof(stackitem));
@@ -148,7 +158,7 @@
   /* ...which will contain... */
   value *new_value;		/* A new symbol value */
   /* ...which might point to... */
-  symbol *new_symbol;		/* (if needed) A new actual symbol */
+  symbol **new_symbol;		/* (if needed) A new actual symbol */
   /* ...which, if possible, will be bound to... */
   value *new_fvalue;		/* (if needed) A new function value */
   /* ...which will point to... */
@@ -166,19 +176,20 @@
   new_value->refcount= 1;
 
   /* Look up the symbol name in the hash table */
-  new_value->content.ptr= *hash(env->symbols, in_string);
+  new_symbol= hash(env->symbols, in_string);
+  new_value->content.ptr= *new_symbol;
 
-  if(new_value->content.ptr==NULL) { /* If symbol was undefined */
+  if(*new_symbol==NULL) { /* If symbol was undefined */
 
     /* Create a new symbol */
-    new_symbol= malloc(sizeof(symbol));
-    new_symbol->val= NULL;	/* undefined value */
-    new_symbol->next= NULL;
-    new_symbol->id= malloc(strlen(in_string)+1);
-    strcpy(new_symbol->id, in_string);
+    (*new_symbol)= malloc(sizeof(symbol));
+    (*new_symbol)->val= NULL;	/* undefined value */
+    (*new_symbol)->next= NULL;
+    (*new_symbol)->id= malloc(strlen(in_string)+1);
+    strcpy((*new_symbol)->id, in_string);
 
     /* Intern the new symbol in the hash table */
-    new_value->content.ptr= new_symbol;
+    new_value->content.ptr= *new_symbol;
 
     /* Try to load the symbol name as an external function, to see if
        we should bind the symbol to a new function pointer value */
@@ -190,8 +201,8 @@
       new_fvalue= malloc(sizeof(value)); /* Create a new value */
       new_fvalue->type=func;	/* The new value is a function pointer */
       new_fvalue->content.ptr=funcptr; /* Store function pointer */
-      new_symbol->val= new_fvalue;      /* Bind the symbol to the new
-                                           function value */
+      (*new_symbol)->val= new_fvalue; /* Bind the symbol to the new
+                                         function value */
       new_fvalue->refcount= 1;
     }
   }
@@ -338,39 +349,72 @@
   return out_item;
 }
 
-
-/* If the top element is a reference, determine if it's a reference to a
-   function, and if it is, toss the reference and execute the function. */
-extern void eval(environment *env)
+/* Recall a value from a symbol, if bound */
+extern void rcl(environment *env)
 {
-  funcp in_func;
-  stackitem* temp= env->head;
+  value *val;
 
-  if(temp==NULL) {
+  if(env->head == NULL) {
     printerr("Stack empty");
     return;
   }
 
-  if(temp->item->type==symb
-     && ((symbol *)(temp->item->content.ptr))->val != NULL
-     && ((symbol *)(temp->item->content.ptr))->val->type == func) {
-    in_func= (funcp)(((symbol *)(temp->item->content.ptr))->val->content.ptr);
-    toss(env);
-    (*in_func)(env);
+  if(env->head->item->type!=symb) {
+    printerr("Not a symbol");
+    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 */
+}
+
+/* If the top element is a symbol, determine if it's bound to a
+   function value, and if it is, toss the symbol and execute the
+   function. */
+extern void eval(environment *env)
+{
+  funcp in_func;
+  value* val;
+  if(env->head==NULL) {
+    printerr("Stack empty");
+    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");
+      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(temp->item->type==func) {
-    in_func= (funcp)(temp->item->content.ptr);
+  /* 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); 
     (*in_func)(env);
     return;
   }
 
-  push(&(env->head), copy(temp));
-  swap(env);
-  toss(env);
 }
 
 /* Make a list. */
@@ -435,7 +479,7 @@
     }
     /* If integer */
     if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
-      push_val(&(env->head), itemp);
+      push_int(&(env->head), itemp);
       break;
     }
     /* Escape ';' with '\' */
@@ -445,7 +489,7 @@
       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;
     }
@@ -535,7 +579,7 @@
   result= (left==right);
   
   toss(env); toss(env);
-  push_val(&(env->head), result);
+  push_int(&(env->head), result);
 }
 
 /* Negates the top element on the stack. */
@@ -550,7 +594,7 @@
 
   val= env->head->item->content.val;
   toss(env);
-  push_val(&(env->head), !val);
+  push_int(&(env->head), !val);
 }
 
 /* Compares the two top elements on the stack and return 0 if they're the
@@ -600,6 +644,47 @@
     toss(env);
 }
 
+/* List all defined words */
+extern void words(environment *env)
+{
+  symbol *temp;
+  int i;
+  
+  for(i= 0; i<HASHTBLSIZE; i++) {
+    temp= env->symbols[i];
+    while(temp!=NULL) {
+      printf("%s\n", temp->id);
+      temp= temp->next;
+    }
+  }
+}
+
+/* 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;