Emacs : Redefining command in Haskell-mode (haskell-mode-hook)

Question

in emacs in haskell-mode, I wanted to change the command

• "C-x C-s"

to

• "C-x C-s" followed by "C-c C-l".

Taking a cue from : Haskell.org : Emacs/Keybindings and simple usage I tried inserting the following variants into the .emacs file but they did not work. Any suggestions as to how I might go about implementing the functionality above would be most welcomed! Thanks.

Variant 1

(defun haskell-hook ()
  (define-key haskell-mode-map (kbd "C-x C-s") (kbd "C-x C-s C-c C-l"))

(add-hook 'haskell-mode-hook 'haskell-hook)

Variant 2

(defun haskell-hook ()
  (define-key haskell-mode-map (kbd "C-x C-s") 'my-haskell-mode-save-buffer)

(defun my-haskell-mode-save-buffer ()
  (interactive)
  (execute-kbd-macro [?\C-s ?\C-x ?\C-c ?\C-l return]))

(add-hook 'haskell-mode-hook 'haskell-hook)

---

---

[EDIT 1] @Tikhon Jelvis : that was definitely a good learning exercise! Thanks. Using the methods outlined in your post I changed your function to :

(defun my-haskell-mode-save-buffer ()
  (interactive)
  (save-buffer)
  (inferior-haskell-load-file)
  (other-window 1))

where the last line programmatically switches the cursor to the interactive window. Thank you.

[EDIT2] Other variants include :

(defun my-haskell-mode-save-buffer ()
  (interactive)
  (execute-kbd-macro (read-kbd-macro "C-c C-l"))
  (other-window 1)) 

and :

(defun my-haskell-mode-save-buffer ()
  (interactive)
  (execute-kbd-macro [?\C-c ?\C-l])
  (other-window 1))

Answer 1

What you want to do is run the function that C-x C-s runs followed by running the function C-c C-l does. You can find out what function is run by some key binding via C-h k. That is, first type C-h k then the key command you're interested in.

This gives us (save-buffer &optional ARGS) for C-x C-s and (inferior-haskell-load-file &optional RELOAD) for C-c C-l. The &optional means exactly what you think it does--that argument is optional, so we don't care about it.

Now write the function that does both of them:

(defun my-haskell-mode-save-buffer ()
  (interactive)
  (save-buffer)
  (inferior-haskell-load-file)) 

Now you can bind this function to C-x C-s in haskell mode exactly how you've been doing it:

(add-hook 'haskell-mode-hook (lambda () 
                                (local-set-key (kbd "C-x C-s") 'my-haskell-mode-save-buffer)))

EDIT: It seems C-c C-l saves your file by default before loading it. This means you can just write

(add-hook 'haskell-mode-hook (lambda ()
                            (local-set-key (kbd "C-x C-s") 'inferior-haskell-load-file)))

and have exactly the same effect without writing your own function. However, I think writing it my way is a good learning exercise :P. That approach works whenever you want to combine multiple different key bindings into one.

Answer 2

The accepted answer does not work in the year 2020. To fix it, you'd have to replace (inferior-haskell-load-file) with (haskell-process-load-file).

So the function after fixing is

(defun haskell-mode-save-load-buffer ()
      (interactive)
      (save-buffer)
      (haskell-process-load-file))