am-br.lisp

(defun am->br (am br amf)
  (flet ((str->arr (str)
           (make-array (length str) :initial-contents (coerce str 'list))))
    (with-accessors ((as diff:original-start) (al diff:original-length)
                     (bs diff:modified-start) (al diff:modified-length))
        (find (find-class 'diff:modified-diff-region)
              (diff:compute-raw-diff (str->arr am)
                                     (str->arr br))
              :key 'class-of)
      (strcat (slice amf 0 as)
              (slice br bs (+ bs bl))
              (slice amf (+ as al))))))