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For C/C++, I have the following to be run when I do M-x compile on a .c/.cpp file

(add-hook 'c++-mode-hook
          (lambda ()
            (set (make-local-variable 'compile-command)
                 (concat "g++ " buffer-file-name " && ./a.out"  ) )))

Now, say I work on some other languages that do not have mode-hook, say R. I want to do something like this:

(add-hook 'r-mode-hook
          (lambda ()
            (set (make-local-variable 'compile-command)
                 (concat "Rscript " buffer-file-name ) )))

After putting above code in my init.el and reloading emacs, there are no errors on startup. I went ahead and open and .r file, but M-x compile does not result in: Rscript . Instead, I got the default prompt from M-x compile: make -k.

Is there a way to do this?

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  • 1
    Why do you believe that r-mode does not have a mode hook? Do you have a link to the source code for r-mode so that we can have a look for ourselves to see whether that is accurate, and/or to make specific suggestions based upon our review of that source code?
    – lawlist
    Commented Jan 30, 2020 at 5:47
  • All major modes defined with define-derived-mode have a mode hook (foo-mode-hook if the mode is named foo-mode), and any major modes defined without that macro are expected to do the same thing. As such, the problem probably isn't what you think it is. I don't have an r-mode so, as @lawlist says, please show us the source for that.
    – phils
    Commented Jan 30, 2020 at 6:15
  • Failing anything else, you could always use after-change-major-mode-hook and (when (derived-mode-p 'r-mode) ...) in your hook function.
    – phils
    Commented Jan 30, 2020 at 6:22
  • It would also be worth checking the value of C-h v major-mode in one of your .r file buffers.
    – phils
    Commented Jan 30, 2020 at 6:23

1 Answer 1

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As far as I know, there's no r-mode in Emacs. Instead, you're probably using ESS's support for R, whose major mode is called ess-r-mode IIRC, so you'd want to use ess-r-mode-hook. But as @phils said: check the value of major-mode to be sure.

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    And most likely «C-h m» will reveal the name of the hook(s) as well
    – Rusi
    Commented Jan 31, 2020 at 5:03

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