--- stack/stack.c	2002/01/31 22:32:59	1.16
+++ stack/stack.c	2002/02/01 23:30:55	1.18
@@ -6,6 +6,8 @@
 #include <stddef.h>
 /* dlopen, dlsym, dlerror */
 #include <dlfcn.h>
+/* assert */
+#include <assert.h>
 
 #define HASHTBLSIZE 65536
 
@@ -13,13 +15,14 @@
 {
   enum {
     value,			/* Integer */
-    string, 
-    ref,	    /* Reference (to an element in the hash table) */ 
+    string,
+    ref,			/* Reference (to an element in the
+                                   hash table) */
     func,			/* Function pointer */
     symbol, 
     list
-  } type;			/* Tells what kind of stack element */
-  
+  } type;			/* Type of stack element */
+
   union {
     void* ptr;			/* Pointer to the content */
     int val;			/* ...or an integer */
@@ -31,10 +34,10 @@
 
 
 typedef stackitem* hashtbl[HASHTBLSIZE]; /* Hash table declaration */
-typedef void (*funcp)(stackitem**); /* Function pointer declaration */
-
+typedef void (*funcp)(stackitem**); /* funcp is a pointer to a
+				       void function (stackitem **) */
 
-/* Initiates a newly created hash table. */
+/* Initialize a newly created hash table. */
 void init_hashtbl(hashtbl out_hash)
 {
   long i;
@@ -48,7 +51,7 @@
 {
   long i= 0;
   unsigned long out_hash= 0;
-  char key= 0;
+  char key= '\0';
   stackitem** position;
   
   while(1){			/* Hash in_string */
@@ -61,15 +64,17 @@
   out_hash= out_hash%HASHTBLSIZE;
   position= &(in_hashtbl[out_hash]);
 
-  while(1){			/* Return position if empty */
-    if(*position==NULL)
+  while(position != NULL){
+    if(*position==NULL)		/* If empty */
       return position;
     
-    if(strcmp(in_string, (*position)->id)==0) /* Return position if match */
+    if(strcmp(in_string, (*position)->id)==0) /* If match */
       return position;
 
     position= &((*position)->next); /* Try next */
   }
+  return NULL;			/* end of list reached without finding
+                                   an empty position */
 }
 
 /* Generic push function. */
@@ -84,6 +89,7 @@
 int push_val(stackitem** stack_head, int in_val) 
 {
   stackitem* new_item= malloc(sizeof(stackitem));
+  assert(new_item != NULL);
   new_item->content.val= in_val;
   new_item->type= value;
 
@@ -114,7 +120,7 @@
   return 1;
 }
 
-/* Define a function a new function in the hash table. */
+/* Define a new function in the hash table. */
 void def_func(hashtbl in_hashtbl, funcp in_func, const char* id)
 {
   stackitem* temp= malloc(sizeof(stackitem));
@@ -162,13 +168,19 @@
   return 1;
 }
 
+void printerr(const char* in_string) {
+  fprintf(stderr, "Err: %s\n", in_string);
+}
+
 /* Discard the top element of the stack. */
 extern void toss(stackitem** stack_head)
 {
   stackitem* temp= *stack_head;
 
-  if((*stack_head)==NULL)
+  if((*stack_head)==NULL) {
+    printerr("Stack empty");
     return;
+  }
   
   if((*stack_head)->type==string)
     free((*stack_head)->content.ptr);
@@ -186,8 +198,10 @@
 /* Prints the top element of the stack. */
 void print_(stackitem** stack_head)
 {
-  if((*stack_head)==NULL)
+  if((*stack_head)==NULL) {
+    printerr("Stack empty");
     return;
+  }
 
   switch((*stack_head)->type) {
   case value:
@@ -230,6 +244,8 @@
   if(*stack_head != NULL) {
     print_st(*stack_head, 1);
     printf("\n");
+  } else {
+    printerr("Stack empty");
   }
 }
 
@@ -239,15 +255,18 @@
 {
   funcp in_func;
 
-  if((*stack_head)==NULL || (*stack_head)->type!=ref)
+  if((*stack_head)==NULL || (*stack_head)->type!=ref) {
+    printerr("Stack empty or not a reference");
     return;
+  }
 
   if(((stackitem*)(*stack_head)->content.ptr)->type==func) {
     in_func= (funcp)((stackitem*)(*stack_head)->content.ptr)->content.ptr;
     toss(stack_head); 
     (*in_func)(stack_head);
     return;
-  }
+  } else
+    printerr("Not a function");
 }
 
 /* Parse input. */
@@ -310,8 +329,10 @@
   void* delimiter;
   stackitem *iterator, *temp, *pack;
 
-  if((*stack_head)==NULL)	/* No delimiter */
+  if((*stack_head)==NULL) {
+    printerr("Stack empty");
     return;
+  }
 
   delimiter= (*stack_head)->content.ptr; /* Get delimiter */
   toss(stack_head);
@@ -344,8 +365,10 @@
   stackitem *temp, *new_head;
 
   /* Is top element a list? */
-  if((*stack_head)==NULL || (*stack_head)->type!=list)
+  if((*stack_head)==NULL || (*stack_head)->type!=list) {
+    printerr("Stack empty or not a list");
     return;
+  }
 
   /* The first list element is the new stack head */
   new_head= temp= (*stack_head)->content.ptr;
@@ -365,7 +388,12 @@
 {
   stackitem* temp= (*stack_head);
   
-  if((*stack_head)==NULL || (*stack_head)->next==NULL)
+  if((*stack_head)==NULL) {
+    printerr("Stack empty");
+    return;
+  }
+
+  if((*stack_head)->next==NULL)
     return;
 
   *stack_head= (*stack_head)->next;
@@ -379,8 +407,10 @@
   void *left, *right;
   int result;
 
-  if((*stack_head)==NULL || (*stack_head)->next==NULL)
+  if((*stack_head)==NULL || (*stack_head)->next==NULL) {
+    printerr("Not enough elements to compare");
     return;
+  }
 
   left= (*stack_head)->content.ptr;
   swap(stack_head);
@@ -396,8 +426,10 @@
 {
   int value;
 
-  if((*stack_head)==NULL || (*stack_head)->type!=value)
+  if((*stack_head)==NULL || (*stack_head)->type!=value) {
+    printerr("Stack empty or element is not a value");
     return;
+  }
 
   value= (*stack_head)->content.val;
   toss(stack_head);
@@ -418,8 +450,10 @@
   stackitem *temp, *value;
 
   if(*stack_head==NULL || (*stack_head)->next==NULL 
-     || (*stack_head)->type!=ref)
+     || (*stack_head)->type!=ref) {
+    printerr("Define what?");
     return;
+  }
 
   temp= (*stack_head)->content.ptr;
   value= (*stack_head)->next;