anchor.diff:  
   (defun string-symbolcase (str) (string-upcase str))
   
  -;;; Subject language primitives
  +;;; String primitives
   
   (defun string-length (str)
     (length str))
  
positive.code:   (replace dest src :start1 dest-index :end1 (+ dest-index len)
             :start2 src-index))
  
  ;;; Vectors
  
  (defun make-vector (len)
    (make-array len))
  
negative.code: (declaim (optimize (debug 2)))
  
  ;;; Subject-language compatibility
  
  (define-symbol-macro true t)
  (define-symbol-macro false nil)
  