I have never written an emacs function before and was wondering if anyone could help me get started. I would like to have a function that takes a highlighted region parses it (by ",") then evaluates each chunk with another function already built into emacs.
The highlighted code may look something like this: x <- function(w=NULL,y=1,z=20){} (r code), and I would like to scrape out w=NULL, y=1, and z=20 then pass each one a function already included with emacs. Any suggestions on how to get started?
A lisp function is defined using defun (you really should read the elisp intro, it will save you a lot of time - "a pint of sweat saves a gallon of blood").
To turn a mere function into an interactive command (which can be called using M-x or bound to a key), you use interactive.
To pass the region (selection) to the function, you use the "r" code:
(defun my-command (beg end)
"Operate on each word in the region."
(interactive "r")
(mapc #'the-emacs-function-you-want-to-call-on-each-arg
;; split the string on any sequence of spaces and commas
(split-string (buffer-substring-no-properties beg end) "[ ,]+")))
Now, copy the form above to the *scratch* emacs buffer, place the point (cursor) on a function, say, mapc or split-string, then hit C-h f RET and you will see a *Help* buffer explaining what the function does.
You can evaluate the function definition by hitting C-M-x while the point is on it (don't forget to replace the-emacs-function-you-want-to-call-on-each-arg with something meaningful), and then test is by selecting w=NULL,y=1,z=20 and hitting M-x my-command RET.
Incidentally, C-h f my-command RET will now show Operate on each word in the region in the *Help* buffer.
