Emacs Lisp - declare functions with a variable/varying name

Question

I'm working on an Emacs Lisp package and one particular feature I would like to add is ability to define functions on the fly - they would follow the same naming convention, but it would help me not having to declare every single one of them manually.

To give an example, I have a basic function called exec, which takes an argument that is the name of executable to launch:

(def exec (cmd)
    (async-shell-command cmd "buffer"))

At the same time, in this particular case, I know the list of the executables that I will want to use - or more precisely, I know how to get a list of them, as it can change over time. So what I would like to do, given the following list of executables:

("a" "b" "c")

is to iterate over them and for each one to create a function with a name exec-[executable] - exec-a, exec-b, exec-c.

Unfortunately, defun does not evaluate the NAME argument so I cannot create the function name dynamically.

PS. The exec command is good enough in itself - it uses completing-read with the list of executables supplied, but I thought the above would be nice addition.

Stefan · Accepted Answer · 2012-10-03 18:51:21Z

13

How 'bout

(dolist (name name-list)
  (defalias (intern (concat "exec-" name))
   `(lambda () ,(format "Run %s via `exec'." name) (interactive) (exec ,name))))

answered Oct 3, 2012 at 18:51

Stefan

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6 Comments

ppb Over a year ago

This is absolutely fantastic, thank you so much :D. Need to study more Emacs Lisp I think :).

phils Over a year ago

You could also use a macro to generate the functions, but this defalias/lambda pairing is very succinct!

event_jr Over a year ago

@Stefan, what considerations did you make in choosing defalias+lambda over a macro?

Stefan Over a year ago

@event_jr: The fact that life is better when you can avoid macros (but don't get me wrong: when you do need macros, life is much better if you can use macros).

eightbitraptor Over a year ago

@Stefan any chance you can clarify what this is doing? particularly the back tick in front of the lambda and the comma's

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