--- stack/stack.c	2002/01/08 18:58:27	1.12
+++ stack/stack.c	2002/01/31 22:32:59	1.16
@@ -11,20 +11,30 @@
 
 typedef struct stack_item
 {
-  enum {value, string, ref, func, symbol, list} type;
+  enum {
+    value,			/* Integer */
+    string, 
+    ref,	    /* Reference (to an element in the hash table) */ 
+    func,			/* Function pointer */
+    symbol, 
+    list
+  } type;			/* Tells what kind of stack element */
+  
   union {
-    void* ptr;
-    int val;
-  } content;
+    void* ptr;			/* Pointer to the content */
+    int val;			/* ...or an integer */
+  } content;			/* Stores a pointer or an integer */
 
-  char* id;
-  struct stack_item* next;
+  char* id;			/* Symbol name */
+  struct stack_item* next;	/* Next element */
 } stackitem;
 
 
-typedef stackitem* hashtbl[HASHTBLSIZE];
-typedef void (*funcp)(stackitem**);
+typedef stackitem* hashtbl[HASHTBLSIZE]; /* Hash table declaration */
+typedef void (*funcp)(stackitem**); /* Function pointer declaration */
+
 
+/* Initiates a newly created hash table. */
 void init_hashtbl(hashtbl out_hash)
 {
   long i;
@@ -33,6 +43,7 @@
     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;
@@ -40,7 +51,7 @@
   char key= 0;
   stackitem** position;
   
-  while(1){
+  while(1){			/* Hash in_string */
     key= in_string[i++];
     if(key=='\0')
       break;
@@ -50,18 +61,18 @@
   out_hash= out_hash%HASHTBLSIZE;
   position= &(in_hashtbl[out_hash]);
 
-  while(1){
+  while(1){			/* Return position if empty */
     if(*position==NULL)
       return position;
     
-    if(strcmp(in_string, (*position)->id)==0)
+    if(strcmp(in_string, (*position)->id)==0) /* Return position if match */
       return position;
 
-    position= &((*position)->next);
+    position= &((*position)->next); /* Try next */
   }
 }
 
-
+/* Generic push function. */
 int push(stackitem** stack_head, stackitem* in_item)
 {
   in_item->next= *stack_head;
@@ -69,6 +80,7 @@
   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 +91,7 @@
   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 +103,7 @@
   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 +114,7 @@
   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));
@@ -110,15 +125,16 @@
   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));
   
   temp->type= symbol;
-
   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;
@@ -128,17 +144,17 @@
   new_item->content.ptr= *hash(in_hash, in_string);
   new_item->type= ref;
 
-  if(new_item->content.ptr==NULL) {
-    if(handle==NULL)
+  if(new_item->content.ptr==NULL) { /* If hash entry empty */
+    if(handle==NULL)		/* If no handle */
       handle= dlopen(NULL, RTLD_LAZY);    
 
-    symbol= dlsym(handle, in_string);
-    if(dlerror()==NULL) 
-      def_func(in_hash, symbol, in_string);
+    symbol= dlsym(handle, in_string); /* Get function pointer */
+    if(dlerror()==NULL) 	/* If existing function pointer */
+      def_func(in_hash, symbol, in_string); /* Store function pointer */
     else
-      def_sym(in_hash, in_string);
+      def_sym(in_hash, in_string); /* Make symbol */
       
-    new_item->content.ptr= *hash(in_hash, in_string);
+    new_item->content.ptr= *hash(in_hash, in_string); /* XXX */
     new_item->type= ref;
   }
 
@@ -146,6 +162,7 @@
   return 1;
 }
 
+/* Discard the top element of the stack. */
 extern void toss(stackitem** stack_head)
 {
   stackitem* temp= *stack_head;
@@ -160,11 +177,13 @@
   free(temp);
 }
 
+/* Print newline. */
 extern void nl()
 {
   printf("\n");
 }
 
+/* Prints the top element of the stack. */
 void print_(stackitem** stack_head)
 {
   if((*stack_head)==NULL)
@@ -187,13 +206,14 @@
   }
 }
 
+/* Prints the top element of the stack and then discards it. */
 extern void print(stackitem** 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)
@@ -204,6 +224,7 @@
   nl();
 }
 
+/* Prints the stack. */
 extern void printstack(stackitem** stack_head)
 {
   if(*stack_head != NULL) {
@@ -212,7 +233,8 @@
   }
 }
 
-
+/* 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(stackitem** stack_head)
 {
   funcp in_func;
@@ -228,6 +250,7 @@
   }
 }
 
+/* Parse input. */
 int stack_read(stackitem** stack_head, hashtbl in_hash, char* in_line) 
 {
   char *temp, *rest;
@@ -238,15 +261,35 @@
   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==';')
-      eval(stack_head);
+  do {
+    /* If string */
+    if((convert= sscanf(in_line, "\"%[^\"\n\r]\" %[^\n\r]", temp, rest))) {
+      push_cstring(stack_head, temp);
+      break;
+    }
+    /* If value */
+    if((convert= sscanf(in_line, "%d %[^\n\r]", &itemp, rest))) {
+      push_val(stack_head, itemp);
+      break;
+    }
+    /* Escape ';' with '\' */
+    if((convert= sscanf(in_line, "\\%c%[^\n\r]", temp, rest))) {
+      temp[1]= '\0'; 
+      push_ref(stack_head, in_hash, temp);
+      break;
+    } 
+    /* If symbol */
+    if((convert= sscanf(in_line, "%[^ ;\n\r]%[^\n\r]", temp, rest))) {
+	push_ref(stack_head, in_hash, temp);
+	break;
+    }
+    /* If ';' */
+    if((convert= sscanf(in_line, "%c%[^\n\r]", temp, rest)) && *temp==';') {
+      eval(stack_head);		/* Evaluate top element */
+      break;
+    }
+  } while(0);
+
 
   free(temp);
 
@@ -261,22 +304,25 @@
   return 1;
 }
 
+/* Make a list. */
 extern void pack(stackitem** stack_head)
 {
   void* delimiter;
   stackitem *iterator, *temp, *pack;
 
-  if((*stack_head)==NULL)
+  if((*stack_head)==NULL)	/* No delimiter */
     return;
 
-  delimiter= (*stack_head)->content.ptr;
+  delimiter= (*stack_head)->content.ptr; /* Get delimiter */
   toss(stack_head);
 
   iterator= *stack_head;
 
+  /* Search for first delimiter */
   while(iterator->next!=NULL && iterator->next->content.ptr!=delimiter)
     iterator= iterator->next;
 
+  /* Extract list */
   temp= *stack_head;
   *stack_head= iterator->next;
   iterator->next= NULL;
@@ -284,6 +330,7 @@
   if(*stack_head!=NULL && (*stack_head)->content.ptr==delimiter)
     toss(stack_head);
 
+  /* Push list */
   pack= malloc(sizeof(stackitem));
   pack->type= list;
   pack->content.ptr= temp;
@@ -291,23 +338,29 @@
   push(stack_head, pack);
 }
 
+/* Relocate elements of the list on the stack. */
 extern void expand(stackitem** stack_head)
 {
   stackitem *temp, *new_head;
 
+  /* Is top element a list? */
   if((*stack_head)==NULL || (*stack_head)->type!=list)
     return;
 
+  /* The first list element is the new stack head */
   new_head= temp= (*stack_head)->content.ptr;
   toss(stack_head);
 
+  /* Search the end of the list */
   while(temp->next!=NULL)
     temp= temp->next;
 
+  /* Connect the the tail of the list with the old stack head */
   temp->next= *stack_head;
-  *stack_head= new_head;
+  *stack_head= new_head;	/* ...and voila! */
 }
 
+/* Swap the two top elements on the stack. */
 extern void swap(stackitem** stack_head)
 {
   stackitem* temp= (*stack_head);
@@ -320,6 +373,7 @@
   (*stack_head)->next= temp;
 } 
 
+/* Compares two elements by reference. */
 extern void eq(stackitem** stack_head)
 {
   void *left, *right;
@@ -337,11 +391,12 @@
   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)
+  if((*stack_head)==NULL || (*stack_head)->type!=value)
     return;
 
   value= (*stack_head)->content.val;
@@ -349,12 +404,15 @@
   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;
@@ -372,6 +430,7 @@
   toss(stack_head); toss(stack_head);
 } 
 
+/* Quit stack. */
 extern void quit()
 {
   exit(EXIT_SUCCESS);