anchor.diff:               (with-slots (length index) condition
                  (format stream "Index ~A out of bounds of (~A ~A), should be nonnegative and ~:*<~A."
                          index 'charseq length)))))
  -;;;;;;;;;; 
  +;;;;;;;;;;
   ;;; struct
   (defstruct (charseq (:conc-name ""))
     (str "" :type (simple-array character) :read-only t)
  
positive.code: (def-charseq-cmp <)
  (def-charseq-cmp >)
  (def-charseq-cmp <=)
  (def-charseq-cmp >=)
negative.code:   (:export invalid-index-error bounding-indices-bad-error
  	   charseq index
  	   make with-dynamic-extent
  	   ref length each sub
  	   = < > <= >= /=
  	   to-string as-string))
  (in-package :charseq)
  