Richard> 125 rassoc is new
    Richard>       (setq temp-ess-dialect (cdr (rassoc ess-dialect
    Richard>       ess-customize-alist)))) 
    Richard> rassoc is part of cl.el and is not automatically part of
    Richard> emacs 19.28.  As an expedient I just (require 'cl).
    Richard> emacs 19.29 seems to be happy with rassoc