--- stack/stack.c	2002/02/15 14:44:24	1.86
+++ stack/stack.c	2002/02/15 18:27:18	1.87
@@ -34,7 +34,7 @@
     int val;			/* ...or an integer */
   } content;			/* Stores a pointer or an integer */
 
-  int refcount;			/* Reference counter */
+  int gc_garb;
 
 } value;
 
@@ -61,6 +61,9 @@
 /* An environment; gives access to the stack and a hash table of
    defined symbols */
 typedef struct {
+  stackitem *gc_ref;
+  int gc_limit, gc_count;
+
   stackitem *head;		/* Head of the stack */
   hashtbl symbols;		/* Hash table of all variable bindings */
   int err;			/* Error flag */
@@ -80,6 +83,9 @@
 {
   int i;
 
+  env->gc_limit= 20;
+  env->gc_count= 0;
+
   env->head= NULL;
   for(i= 0; i<HASHTBLSIZE; i++)
     env->symbols[i]= NULL;
@@ -94,39 +100,6 @@
   fprintf(stderr, "Err: %s\n", in_string);
 }
 
-/* Throw away a value */
-void free_val(value *val){
-  stackitem *item, *temp;
-
-  val->refcount--;		/* Decrease the reference count */
-  if(val->refcount == 0){
-    switch (val->type){		/* and free the contents if necessary */
-    case string:
-      free(val->content.ptr);
-      break;
-    case list:			/* lists needs to be freed recursively */
-      item=val->content.ptr;
-      while(item != NULL) {	/* for all stack items */
-	free_val(item->item);	/* free the value */
-	temp=item->next;	/* save next ptr */
-	free(item);		/* free the stackitem */
-	item=temp;		/* go to next stackitem */
-      }
-      break;
-    case integer:
-    case func:
-      break;
-    case symb:
-      free(((symbol*)(val->content.ptr))->id);
-      if(((symbol*)(val->content.ptr))->val!=NULL)
-	free_val(((symbol*)(val->content.ptr))->val);
-      free(val->content.ptr);
-      break;
-    }
-    free(val);		/* Free the actual value structure */
-  }
-}
-
 /* Discard the top element of the stack. */
 extern void toss(environment *env)
 {
@@ -138,7 +111,6 @@
     return;
   }
   
-  free_val(env->head->item);	/* Free the value */
   env->head= env->head->next;	/* Remove the top stack item */
   free(temp);			/* Free the old top stack item */
 }
@@ -172,12 +144,112 @@
   }
 }
 
+extern void gc_init(environment*);
+
+value* new_val(environment *env) {
+  value *nval= malloc(sizeof(value));
+  stackitem *nitem= malloc(sizeof(stackitem));
+
+  if(env->gc_count >= env->gc_limit)
+    gc_init(env);
+
+  nval->content.ptr= NULL;
+
+  nitem->item= nval;
+  nitem->next= env->gc_ref;
+  env->gc_ref= nitem;
+
+  env->gc_count++;
+
+  return nval;
+}
+
+void gc_mark(value *val) {
+  stackitem *iterator;
+
+  if(val==NULL || val->gc_garb==0)
+    return;
+
+  val->gc_garb= 0;
+
+  if(val->type==list) {
+    iterator= val->content.ptr;
+
+    while(iterator!=NULL) {
+      gc_mark(iterator->item);
+      iterator= iterator->next;
+    }
+  }
+}
+
+extern void gc_init(environment *env) {
+  stackitem *new_head= NULL, *titem, *iterator= env->gc_ref;
+  symbol *tsymb;
+  int i;
+
+  while(iterator!=NULL) {
+    iterator->item->gc_garb= 1;
+    iterator= iterator->next;
+  }
+
+  /* Mark */
+  iterator= env->head;
+  while(iterator!=NULL) {
+    gc_mark(iterator->item);
+    iterator= iterator->next;
+  }
+
+  for(i= 0; i<HASHTBLSIZE; i++) {
+    tsymb= env->symbols[i];
+    while(tsymb!=NULL) {
+      gc_mark(tsymb->val);
+      tsymb= tsymb->next;
+    }
+  }
+
+  env->gc_count= 0;
+
+  /* Sweep */
+  while(env->gc_ref!=NULL) {
+    if(env->gc_ref->item->gc_garb) {
+      switch(env->gc_ref->item->type) {
+      case string:
+	free(env->gc_ref->item->content.ptr);
+	break;
+      case integer:
+	break;
+      case list:
+	while(env->gc_ref->item->content.ptr!=NULL) {
+	  titem= env->gc_ref->item->content.ptr;
+	  env->gc_ref->item->content.ptr= titem->next;
+	  free(titem);
+	}
+	break;
+      default:
+	break;
+      }
+      free(env->gc_ref->item);
+      titem= env->gc_ref->next;
+      free(env->gc_ref);
+      env->gc_ref= titem;
+    } else {
+      titem= env->gc_ref->next;
+      env->gc_ref->next= new_head;
+      new_head= env->gc_ref;
+      env->gc_ref= titem;
+      env->gc_count++;
+    }
+  }
+
+  env->gc_limit= env->gc_count+20;
+  env->gc_ref= new_head;
+}
+
 /* Push a value onto the stack */
 void push_val(environment *env, value *val)
 {
   stackitem *new_item= malloc(sizeof(stackitem));
   new_item->item= val;
-  val->refcount++;
   new_item->next= env->head;
   env->head= new_item;
 }
@@ -185,11 +257,10 @@
 /* Push an integer onto the stack. */
 void push_int(environment *env, int in_val) 
 {
-  value *new_value= malloc(sizeof(value));
+  value *new_value= new_val(env);
   
   new_value->content.val= in_val;
   new_value->type= integer;
-  new_value->refcount= 0;
 
   push_val(env, new_value);
 }
@@ -197,12 +268,11 @@
 /* Copy a string onto the stack. */
 void push_cstring(environment *env, const char *in_string)
 {
-  value *new_value= malloc(sizeof(value));
+  value *new_value= new_val(env);
 
   new_value->content.ptr= malloc(strlen(in_string)+1);
   strcpy(new_value->content.ptr, in_string);
   new_value->type= string;
-  new_value->refcount= 0;
 
   push_val(env, new_value);
 }
@@ -265,11 +335,10 @@
   const char *dlerr;		/* Dynamic linker error */
   char *mangled;		/* Mangled function name */
 
-  new_value= malloc(sizeof(value));
+  new_value= new_val(env);
 
   /* The new value is a symbol */
   new_value->type= symb;
-  new_value->refcount= 1;
 
   /* Look up the symbol name in the hash table */
   new_symbol= hash(env->symbols, in_string);
@@ -301,12 +370,11 @@
       dlerr=dlerror();
     }
     if(dlerr==NULL) {		/* If a function was found */
-      new_fvalue= malloc(sizeof(value)); /* Create a new value */
+      new_fvalue= new_val(env); /* Create a new value */
       new_fvalue->type=func;	/* The new value is a function pointer */
       new_fvalue->content.ptr=funcptr; /* Store function pointer */
       (*new_symbol)->val= new_fvalue; /* Bind the symbol to the new
                                          function value */
-      new_fvalue->refcount= 1;
     }
   }
   push_val(env, new_value);
@@ -534,7 +602,6 @@
     /* If it's a list */
   case list:
     temp_val= env->head->item;
-    env->head->item->refcount++;
     toss(env);
     if(env->err) return;
     iterator= (stackitem*)temp_val->content.ptr;
@@ -545,7 +612,6 @@
 	toss(env);
 	if(env->err) return;
 	if(iterator->next == NULL){
-	  free_val(temp_val);
 	  goto eval_start;
 	}
 	eval(env);
@@ -553,7 +619,6 @@
       }
       iterator= iterator->next;
     }
-    free_val(temp_val);
     return;
 
   default:
@@ -618,10 +683,9 @@
   }
 
   /* Push list */
-  pack= malloc(sizeof(value));
+  pack= new_val(env);
   pack->type= list;
   pack->content.ptr= temp;
-  pack->refcount= 0;
 
   push_val(env, pack);
   rev(env);
@@ -652,7 +716,6 @@
   /* The first list element is the new stack head */
   new_head= temp= env->head->item->content.ptr;
 
-  env->head->item->refcount++;
   toss(env);
 
   /* Find the end of the list */
@@ -738,19 +801,15 @@
   sym=env->head->item->content.ptr;
 
   /* if the symbol was bound to something else, throw it away */
-  if(sym->val != NULL)
-    free_val(sym->val);
 
   /* Bind the symbol to the value */
   sym->val= env->head->next->item;
-  sym->val->refcount++;		/* Increase the reference counter */
 
   toss(env); toss(env);
 } 
 
 extern void clear(environment *);
 void forget_sym(symbol **);
-extern void words(environment *);
 
 /* Quit stack. */
 extern void quit(environment *env)
@@ -767,6 +826,8 @@
     env->symbols[i]= NULL;
   }
 
+  gc_init(env);
+
   if(env->free_string!=NULL)
     free(env->free_string);
   
@@ -804,9 +865,6 @@
   temp= *hash_entry;
   *hash_entry= (*hash_entry)->next;
   
-  if(temp->val!=NULL) {
-    free_val(temp->val);
-  }
   free(temp->id);
   free(temp);
 }
@@ -921,15 +979,12 @@
      && env->head->next->item->type==string) {
     a_val= env->head->item;
     b_val= env->head->next->item;
-    a_val->refcount++;
-    b_val->refcount++;
     toss(env); if(env->err) return;
     toss(env); if(env->err) return;
     len= strlen(a_val->content.ptr)+strlen(b_val->content.ptr)+1;
     new_string= malloc(len);
     strcpy(new_string, b_val->content.ptr);
     strcat(new_string, a_val->content.ptr);
-    free_val(a_val); free_val(b_val);
     push_cstring(env, new_string);
     free(new_string);
     return;
@@ -942,16 +997,11 @@
     return;
   }
   a=env->head->item->content.val;
-  toss(env);
-  if(env->err) return;
-  if(env->head->item->refcount == 1)
-    env->head->item->content.val += a;
-  else {
-    b=env->head->item->content.val;
-    toss(env);
-    if(env->err) return;
-    push_int(env, a+b);
-  }
+  toss(env); if(env->err) return;
+  
+  b=env->head->item->content.val;
+  toss(env); if(env->err) return;
+  push_int(env, a+b);
 }
 
 /* "-" */
@@ -971,16 +1021,10 @@
     return;
   }
   a=env->head->item->content.val;
-  toss(env);
-  if(env->err) return;
-  if(env->head->item->refcount == 1)
-    env->head->item->content.val -= a;
-  else {
-    b=env->head->item->content.val;
-    toss(env);
-    if(env->err) return;
-    push_int(env, b-a);
-  }
+  toss(env); if(env->err) return;
+  b=env->head->item->content.val;
+  toss(env); if(env->err) return;
+  push_int(env, b-a);
 }
 
 /* ">" */
@@ -1000,28 +1044,20 @@
     return;
   }
   a=env->head->item->content.val;
-  toss(env);
-  if(env->err) return;
-  if(env->head->item->refcount == 1)
-    env->head->item->content.val = (env->head->item->content.val > a);
-  else {
-    b=env->head->item->content.val;
-    toss(env);
-    if(env->err) return;
-    push_int(env, b>a);
-  }
+  toss(env); if(env->err) return;
+  b=env->head->item->content.val;
+  toss(env); if(env->err) return;
+  push_int(env, b>a);
 }
 
 /* Return copy of a value */
-value *copy_val(value *old_value){
+value *copy_val(environment *env, value *old_value){
   stackitem *old_item, *new_item, *prev_item;
 
-  value *new_value=malloc(sizeof(value));
+  value *new_value=new_val(env);
 
   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;
@@ -1042,7 +1078,7 @@
 
     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->item=copy_val(env, 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
@@ -1064,7 +1100,7 @@
     env->err=1;
     return;
   }
-  push_val(env, copy_val(env->head->item));
+  push_val(env, copy_val(env, env->head->item));
 }
 
 /* "if", If-Then */
@@ -1147,11 +1183,9 @@
   }
 
   loop= env->head->item;
-  loop->refcount++;
   toss(env); if(env->err) return;
 
   test= env->head->item;
-  test->refcount++;
   toss(env); if(env->err) return;
 
   do {
@@ -1175,9 +1209,6 @@
     }
   
   } while(truth);
-
-  free_val(test);
-  free_val(loop);
 }
 
 /* "for"; For-loop */
@@ -1199,11 +1230,9 @@
   }
 
   loop= env->head->item;
-  loop->refcount++;
   toss(env); if(env->err) return;
 
   foo= env->head->item;
-  foo->refcount++;
   toss(env); if(env->err) return;
 
   iterator= foo->content.ptr;
@@ -1214,9 +1243,6 @@
     eval(env); if(env->err) return;
     iterator= iterator->next;
   }
-
-  free_val(loop);
-  free_val(foo);
 }
 
 /* "to" */
@@ -1254,9 +1280,8 @@
       push_int(env, i);
   }
 
-  temp_val= malloc(sizeof(value));
+  temp_val= new_val(env);
   temp_val->content.ptr= env->head;
-  temp_val->refcount= 0;
   temp_val->type= list;
   env->head= temp_head;
   push_val(env, temp_val);