anchor.diff:  
   ;;----------------
   
  -(v-def-glsl-template-fun iterator-reached-end (state limit)
  -                         "(~a >= ~a)"
  +(v-def-glsl-template-fun iterator-limit-check (limit state)
  +                         "(~a < ~a)"
                            (range-iter-state range-iter-state) :bool)
   
  -(v-defun iterator-reached-end ((seq range) (state :int) (limit :int)
  -                               (from-end :bool))
  +(v-defun iterator-limit-check ((limit :int) (state :int) (from-end :bool))
     (if from-end (> state limit) (< state limit)))
  +
  +(v-define-compiler-macro iterator-limit-check ((limit :int) (state :int))
  +  `(< ,limit ,state))
   
   ;;----------------
   
  
positive.code:                         (range-end seq)
                          (range-start seq))))
  
  ;;----------------
  
  (v-def-glsl-template-fun
  
negative.code:                         (range-start seq)
                          (range-end seq))))
  
  (v-define-compiler-macro limit ((seq range))
    `(range-iter-state (range-end ,seq)))
  
  ;;----------------
  
  (v-defun create-iterator-state ((seq range))
  