I’m still an elisp novice, so maybe I’m wrong, but anyway: it might be better to use `mapc’ or `dolist’ instead of `mapcar’ in this example. It doesn’t really matter, but as a matter of principle, since we’re here to learn how to do Emacs better, I think those might be the more “idiomatic” functions to use. Of course, please do correct me if I’m wrong! 
– Adam 2015-10-09 21:34 UTC