anchor.diff:                          (range-end seq)
                           (range-start seq))))
   
  +(v-define-compiler-macro create-iterator-state ((seq range))
  +  `(range-iter-state (range-start ,seq)))
  +
   ;;----------------
   
   (v-def-glsl-template-fun
  
positive.code:   :return
    ())
  
  ;;----------------
  
  (v-defun make-sequence-like ((seq range) (length :int))
  
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))
  