--- stack/stack.c	2002/01/08 14:31:23	1.9
+++ stack/stack.c	2002/01/31 21:47:20	1.15
@@ -25,6 +25,8 @@
 typedef stackitem* hashtbl[HASHTBLSIZE];
 typedef void (*funcp)(stackitem**);
 
+
+/* Initiates a newly created hash table. */
 void init_hashtbl(hashtbl out_hash)
 {
   long i;
@@ -33,6 +35,7 @@
     out_hash[i]= NULL;
 }
 
+/* Returns a pointer to an element in the hash table. */
 stackitem** hash(hashtbl in_hashtbl, const char* in_string)
 {
   long i= 0;
@@ -61,7 +64,7 @@
   }
 }
 
-
+/* Generic push function. */
 int push(stackitem** stack_head, stackitem* in_item)
 {
   in_item->next= *stack_head;
@@ -69,6 +72,7 @@
   return 1;
 }
 
+/* Push a value on the stack. */
 int push_val(stackitem** stack_head, int in_val) 
 {
   stackitem* new_item= malloc(sizeof(stackitem));
@@ -79,6 +83,7 @@
   return 1;
 }
 
+/* Copy a string onto the stack. */
 int push_cstring(stackitem** stack_head, const char* in_string)
 {
   stackitem* new_item= malloc(sizeof(stackitem));
@@ -90,6 +95,7 @@
   return 1;
 }
 
+/* Create a new hash entry. */
 int mk_hashentry(hashtbl in_hashtbl, stackitem* in_item, const char* id)
 {
   in_item->id= malloc(strlen(id)+1);
@@ -100,6 +106,7 @@
   return 1;
 }
 
+/* Define a function a new function in the hash table. */
 void def_func(hashtbl in_hashtbl, funcp in_func, const char* id)
 {
   stackitem* temp= malloc(sizeof(stackitem));
@@ -110,6 +117,7 @@
   mk_hashentry(in_hashtbl, temp, id);
 }
 
+/* Define a new symbol in the hash table. */
 void def_sym(hashtbl in_hashtbl, const char* id)
 {
   stackitem* temp= malloc(sizeof(stackitem));
@@ -119,6 +127,7 @@
   mk_hashentry(in_hashtbl, temp, id);
 }
 
+/* Push a reference to an entry in the hash table onto the stack. */
 int push_ref(stackitem** stack_head, hashtbl in_hash, const char* in_string)
 {
   static void* handle= NULL;
@@ -146,6 +155,7 @@
   return 1;
 }
 
+/* Discard the top element of the stack. */
 extern void toss(stackitem** stack_head)
 {
   stackitem* temp= *stack_head;
@@ -160,12 +170,14 @@
   free(temp);
 }
 
+/* Print newline. */
 extern void nl()
 {
   printf("\n");
 }
 
-void prin(stackitem** stack_head)
+/* Prints the top element of the stack. */
+void print_(stackitem** stack_head)
 {
   if((*stack_head)==NULL)
     return;
@@ -187,23 +199,25 @@
   }
 }
 
+/* Prints the top element of the stack and then discards it. */
 extern void print(stackitem** stack_head)
 {
-  prin(stack_head);
+  print_(stack_head);
   toss(stack_head);
 }
 
-/* print_stack(stack); */
+/* Only to be called by function printstack. */
 void print_st(stackitem* stack_head, long counter)
 { 
   if(stack_head->next != NULL)
     print_st(stack_head->next, counter+1);
 
   printf("%ld: ", counter);
-  prin(&stack_head);
+  print_(&stack_head);
   nl();
 }
 
+/* Prints the stack. */
 extern void printstack(stackitem** stack_head)
 {
   if(*stack_head != NULL) {
@@ -212,7 +226,9 @@
   }
 }
 
-
+/* If the top element is a reference, determine if it's a reference to a
+   function, and if it is execute and pop the reference and execute the
+   function. */
 extern void eval(stackitem** stack_head)
 {
   funcp in_func;
@@ -228,6 +244,7 @@
   }
 }
 
+/* Parse input. */
 int stack_read(stackitem** stack_head, hashtbl in_hash, char* in_line) 
 {
   char *temp, *rest;
@@ -238,15 +255,34 @@
   temp= malloc(inlength);
   rest= malloc(inlength);
 
-  if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest)) >= 1)
-    push_cstring(stack_head, temp);
-  else if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest)) >= 1)
-    push_val(stack_head, itemp);
-  else if((convert= sscanf(in_line, "%[^ ;\n\r]%[^\n\r]", temp, rest)) >= 1) 
-    push_ref(stack_head, in_hash, temp);
-  else if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest)) >= 1)
-    if(*temp==';')
+  do {
+    if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
+      push_cstring(stack_head, temp);
+      break;
+    }
+ 
+    if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
+      push_val(stack_head, itemp);
+      break;
+    }
+ 
+    if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
+      temp[1]= '\0'; 
+      push_ref(stack_head, in_hash, temp);
+      break;
+    } 
+      
+    if((convert= sscanf(in_line, "%[^ ;\n\r]%[^\n\r]", temp, rest))) {
+	push_ref(stack_head, in_hash, temp);
+	break;
+    }
+  
+    if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest)) && *temp==';') {
       eval(stack_head);
+      break;
+    }
+  } while(0);
+
 
   free(temp);
 
@@ -261,6 +297,7 @@
   return 1;
 }
 
+/* Make a list. */
 extern void pack(stackitem** stack_head)
 {
   void* delimiter;
@@ -291,6 +328,7 @@
   push(stack_head, pack);
 }
 
+/* Push elements of the list on the stack. */
 extern void expand(stackitem** stack_head)
 {
   stackitem *temp, *new_head;
@@ -308,6 +346,77 @@
   *stack_head= new_head;
 }
 
+/* Swap the two top elements on the stack. */
+extern void swap(stackitem** stack_head)
+{
+  stackitem* temp= (*stack_head);
+  
+  if((*stack_head)==NULL || (*stack_head)->next==NULL)
+    return;
+
+  *stack_head= (*stack_head)->next;
+  temp->next= (*stack_head)->next;
+  (*stack_head)->next= temp;
+} 
+
+/* Compares two elements by reference. */
+extern void eq(stackitem** stack_head)
+{
+  void *left, *right;
+  int result;
+
+  if((*stack_head)==NULL || (*stack_head)->next==NULL)
+    return;
+
+  left= (*stack_head)->content.ptr;
+  swap(stack_head);
+  right= (*stack_head)->content.ptr;
+  result= (left==right);
+  
+  toss(stack_head); toss(stack_head);
+  push_val(stack_head, (left==right));
+}
+
+/* Negates the top element on the stack. */
+extern void not(stackitem** stack_head)
+{
+  int value;
+
+  if((*stack_head)==NULL)
+    return;
+
+  value= (*stack_head)->content.val;
+  toss(stack_head);
+  push_val(stack_head, !value);
+}
+
+/* Compares the two top elements on the stack and return 0 if they're the
+   same. */
+extern void neq(stackitem** stack_head)
+{
+  eq(stack_head);
+  not(stack_head);
+}
+
+/* Give a symbol some content. */
+extern void def(stackitem** stack_head)
+{
+  stackitem *temp, *value;
+
+  if(*stack_head==NULL || (*stack_head)->next==NULL 
+     || (*stack_head)->type!=ref)
+    return;
+
+  temp= (*stack_head)->content.ptr;
+  value= (*stack_head)->next;
+  temp->content= value->content;
+  value->content.ptr=NULL;
+  temp->type= value->type;
+
+  toss(stack_head); toss(stack_head);
+} 
+
+/* Quit stack. */
 extern void quit()
 {
   exit(EXIT_SUCCESS);
@@ -328,8 +437,7 @@
     printf("okidok\n ");
   }
 
-
-  return EXIT_SUCCESS;
+  exit(EXIT_SUCCESS);
 }
 
 /* Local Variables: */