--- stack/stack.c	2002/03/17 12:49:27	1.116
+++ stack/stack.c	2002/03/20 13:20:29	1.118
@@ -21,8 +21,8 @@
 	     Teddy Hogeborn <teddy@fukt.bth.se>
 */
 
-#define CAR(X) (X->content.c->car)
-#define CDR(X) (X->content.c->cdr)
+#define CAR(X) ((X)->content.c->car)
+#define CDR(X) ((X)->content.c->cdr)
 
 /* printf, sscanf, fgets, fprintf, fopen, perror */
 #include <stdio.h>
@@ -62,7 +62,6 @@
   env->gc_ref= NULL;
 
   env->head= new_val(env);
-  env->head->type= empty;
   for(i= 0; i<HASHTBLSIZE; i++)
     env->symbols[i]= NULL;
   env->err= 0;
@@ -124,8 +123,11 @@
   value *nval= malloc(sizeof(value));
   stackitem *nitem= malloc(sizeof(stackitem));
 
+  assert(nval != NULL);
+  assert(nitem != NULL);
+
   nval->content.ptr= NULL;
-  nval->type= integer;
+  nval->type= empty;
 
   nitem->item= nval;
   nitem->next= env->gc_ref;
@@ -336,6 +338,7 @@
   int length= strlen(in_string)+1;
 
   new_value->content.ptr= malloc(length);
+  assert(new_value != NULL);
   env->gc_count += length;
   strcpy(new_value->content.ptr, in_string);
   new_value->type= string;
@@ -350,6 +353,7 @@
   char *new_string, *current;
 
   new_string= malloc((strlen(old_string)*2)+4);
+  assert(new_string != NULL);
   strcpy(new_string, "sx_");	/* Stack eXternal */
   current= new_string+3;
   while(old_string[0] != '\0'){
@@ -419,9 +423,11 @@
 
     /* Create a new symbol */
     (*new_symbol)= malloc(sizeof(symbol));
+    assert((*new_symbol) != NULL);
     (*new_symbol)->val= NULL;	/* undefined value */
     (*new_symbol)->next= NULL;
     (*new_symbol)->id= malloc(strlen(in_string)+1);
+    assert((*new_symbol)->id != NULL);
     strcpy((*new_symbol)->id, in_string);
 
     /* Intern the new symbol in the hash table */
@@ -499,8 +505,11 @@
 }    
 
 /* Print a value */
-void print_val(value *val, int noquote)
+void print_val(value *val, int noquote, stackitem *stack)
 {
+  stackitem *titem, *tstack;
+  int depth;
+
   switch(val->type) {
   case empty:
     printf("[]");
@@ -525,20 +534,56 @@
     break;
   case tcons:
     printf("[ ");
+    tstack= stack;
     do {
-      print_val(CAR(val), noquote);
+      titem=malloc(sizeof(stackitem));
+      assert(titem != NULL);
+      titem->item=val;
+      titem->next=tstack;
+      tstack=titem;		/* Put it on the stack */
+      /* Search a stack of values being printed to see if we are already
+	 printing this value */
+      titem=tstack;
+      depth=0;
+      while(titem != NULL && titem->item != CAR(val)){
+	titem=titem->next;
+	depth++;
+      }
+      if(titem != NULL){	/* If we found it on the stack, */
+	printf("#%d#", depth);	/* print a depth reference */
+      } else {
+	print_val(CAR(val), noquote, tstack);
+      }
       val= CDR(val);
       switch(val->type){
       case empty:
 	break;
       case tcons:
-	printf(" ");
+	/* Search a stack of values being printed to see if we are already
+	   printing this value */
+	titem=tstack;
+	depth=0;
+	while(titem != NULL && titem->item != val){
+	  titem=titem->next;
+	  depth++;
+	}
+	if(titem != NULL){	/* If we found it on the stack, */
+	  printf(" . #%d#", depth); /* print a depth reference */
+	} else {
+	  printf(" ");
+	}
 	break;
       default:
 	printf(" . ");		/* Improper list */
-	print_val(val, noquote);
+	print_val(val, noquote, tstack);
       }
-    } while(val->type == tcons);
+    } while(val->type == tcons && titem == NULL);
+    titem=tstack;
+    while(titem != stack){
+      tstack=titem->next;
+      free(titem);
+      titem=tstack;
+    }
     printf(" ]");
     break;
   }
@@ -551,7 +596,7 @@
     env->err= 1;
     return;
   }
-  print_val(CAR(env->head), 0);
+  print_val(CAR(env->head), 0, NULL);
   nl();
 }
 
@@ -570,7 +615,7 @@
     env->err= 1;
     return;
   }
-  print_val(CAR(env->head), 1);
+  print_val(CAR(env->head), 1, NULL);
 }
 
 /* Prints the top element of the stack and then discards it. */
@@ -587,7 +632,7 @@
   if(CDR(stack_head)->type != empty)
     print_st(CDR(stack_head), counter+1);
   printf("%ld: ", counter);
-  print_val(CAR(stack_head), 0);
+  print_val(CAR(stack_head), 0, NULL);
   nl();
 }
 
@@ -764,7 +809,6 @@
 
   old_head= CAR(env->head);
   new_head= new_val(env);
-  new_head->type= empty;
   while(old_head->type != empty) {
     item= old_head;
     old_head= CDR(old_head);
@@ -780,7 +824,6 @@
   value *iterator, *temp, *ending;
 
   ending=new_val(env);
-  ending->type=empty;
 
   iterator= env->head;
   if(iterator->type == empty
@@ -1066,7 +1109,7 @@
   }
 
   if(myenv.interactive) {
-    printf("Stack version $Revision: 1.116 $\n\
+    printf("Stack version $Revision: 1.118 $\n\
 Copyright (C) 2002  Mats Alritzson and Teddy Hogeborn\n\
 Stack comes with ABSOLUTELY NO WARRANTY; for details type 'warranty;'.\n\
 This is free software, and you are welcome to redistribute it\n\
@@ -1126,6 +1169,7 @@
     toss(env); if(env->err) return;
     len= strlen(a_val->content.ptr)+strlen(b_val->content.ptr)+1;
     new_string= malloc(len);
+    assert(new_string != NULL);
     strcpy(new_string, b_val->content.ptr);
     strcat(new_string, a_val->content.ptr);
     push_cstring(env, new_string);
@@ -1725,6 +1769,7 @@
     }
     
     env->in_string= malloc(strlen(CAR(env->head)->content.ptr)+1);
+    assert(env->in_string != NULL);
     env->free_string= env->in_string; /* Save the original pointer */
     strcpy(env->in_string, CAR(env->head)->content.ptr);
     toss(env); if(env->err) return;
@@ -1732,6 +1777,7 @@
   
   inlength= strlen(env->in_string)+1;
   match= malloc(inlength);
+  assert(match != NULL);
 
   if(sscanf(env->in_string, blankform, &readlength) != EOF
      && readlength != -1) {