--- stack/stack.c	2002/02/08 00:25:57	1.54
+++ stack/stack.c	2002/02/08 00:59:34	1.55
@@ -948,3 +948,58 @@
   if(env->err) return;
   push_int(&(env->head), a+b);
 }
+
+/* Return copy of a value */
+value *copy_val(value *old_value){
+  stackitem *old_item, *new_item, *prev_item;
+
+  value *new_value=malloc(sizeof(value));
+
+  new_value->type=old_value->type;
+  new_value->refcount=0;	/* This is increased if/when this
+				   value is referenced somewhere, like
+				   in a stack item or a variable */
+  switch(old_value->type){
+  case integer:
+    new_value->content.val=old_value->content.val;
+    break;
+  case string:
+    (char *)(new_value->content.ptr)
+      = strdup((char *)(old_value->content.ptr));
+    break;
+  case func:
+  case symb:
+    new_value->content.ptr=old_value->content.ptr;
+    break;
+  case list:
+    new_value->content.ptr=NULL;
+
+    prev_item=NULL;
+    old_item=(stackitem *)(old_value->content.ptr);
+
+    while(old_item != NULL) {	/* While list is not empty */
+      new_item= malloc(sizeof(stackitem));
+      new_item->item=copy_val(old_item->item); /* recurse */
+      new_item->next=NULL;
+      if(prev_item != NULL)	/* If this wasn't the first item */
+	prev_item->next=new_item; /* point the previous item to the
+                                     new item */
+      else
+	new_value->content.ptr=new_item;
+      old_item=old_item->next;
+      prev_item=new_item;
+    }	  
+    break;
+  }
+  return new_value;
+}
+
+/* duplicates an item on the stack */
+extern void dup(environment *env) {
+  if((env->head)==NULL) {
+    printerr("Too Few Arguments");
+    env->err=1;
+    return;
+  }
+  push_val(&(env->head), copy_val(env->head->item));
+}