I'm a happy user of Emacs and SLIME.

It looks like SLIME is aware of only files with the extension ".lisp" and not others such as ".cl" or ".asd"

How can I make SLIME aware of and work with different file extensions? Thanks.

  • What do you mean by "aware of"?
    – nanny
    Dec 23, 2015 at 20:33
  • When I start out with an *.asd file on SLIME, the C-c C-c just doesn't work though *.asd is a proper lisp file. So I had to change the extension to .lisp and I think that's redundant work.
    – Terry
    Dec 23, 2015 at 22:27

1 Answer 1


Try adding:

(add-to-list 'auto-mode-alist '("\\.cl\\'" . slime-mode))
(add-to-list 'auto-mode-alist '("\\.asd\\'" . slime-mode))

to your init/config file. Then files with those extensions will use slime-mode by default. This pattern of (add-to-list 'auto-mode-alist '("\\.EXTENSION\\'" . MODE)) is a good way to have files with the extension EXTENSION open in the mode MODE. Just be careful that you have the "\\.EXTENSION\\'" part, which is a regular expression, formatted correctly (with slashes and quotes in the right places), or you will will not get the results you want.

  • It was looking likely to work but it didn't. I added those lines to my CMUCL init script at ~/.cmucl-init.lisp and then it said : Error in KERNEL:%COERCE-TO-FUNCTION: the function ADD-TO-LIST is undefined. I deleted them from cmucl-init and added to ~/.emacs, but this time it made no difference, .cl files are still not evaluated.
    – Terry
    Dec 23, 2015 at 22:40
  • It definitely needs to be added to your .emacs and not the other init script you mention. Also, it probably should be added after slime is loaded
    – elethan
    Dec 23, 2015 at 22:49
  • @Ömer You'll want to use lisp-mode instead of slime-mode.
    – nanny
    Dec 29, 2015 at 14:17

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