how to get a variable to represent a function name for "symbol-function()"

Question

I am learning how to program in emacs lisp. I thought I would write a simple function that prints a function definition to the messages buffer. This works fine:

(let (
(fDefAsString (symbol-function 'scroll-down)) 
)
(message "%s" fDefAsString)
(switch-to-buffer-other-frame "*Messages*"))

but I wanted this to be a function that could take an argument, the argument being the name of the function whose definition I want to see. So I tried this:

(defun message-function-definition (nameOfFunction)
(let (
(fDefAsString (symbol-function 'nameOfFunction)) 
)
(message "%s" fDefAsString)
(switch-to-buffer-other-frame "*Messages*")))

and then I wrote this:

(message-function-definition 'scroll-down)

Then I ran "eval-buffer".

I keep getting this error:

Debugger entered--Lisp error: (void-function nameOfFunction) symbol-function(nameOfFunction) (let ((fDefAsString ...)) (message "%s" fDefAsString) (switch-to-buffer-other-frame "Messages")) message-function-definition(scroll-down) eval((message-function-definition (quote scroll-down))) eval-last-sexp-1(nil) eval-last-sexp(nil) call-interactively(eval-last-sexp nil nil) recursive-edit() byte-code("\306 @\307=\203!

I've tried quoting, unquoting, and I've tried to use "nameOfFunction" but I can not get this to work. What am I doing wrong?

event_jr · Accepted Answer · 2012-08-18 22:35:20Z

1

Did you try unquoting? This works for me:

(defun message-function-definition (nameOfFunction)
  (let ((fDefAsString (symbol-function nameOfFunction)))
    (message "%s" fDefAsString)
    (switch-to-buffer-other-frame "*Messages*")))

Some hints:

Your code is not indented correctly. If you select the region and re-indent with tab, it'll be easier to read.
You should spend a couple of hours working through the "Emacs Lisp Intro", you will have a much better idea of how things work in Emacs-lisp, rather than figuring it all by asking one question at a time on StackOverflow.
symbol-function is not designed to show a human readable definition of the function. In most cases you won't really see anything useful.

Try this:
```
(find-function-other-window 'scroll-down)
```

answered Aug 18, 2012 at 22:35

event_jr

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5 Comments

cerhovice Over a year ago

if I put (find-function-other-window 'scroll-down) in an empty buffer and run eval-buffer I get : "Debugger entered--Lisp error: (error "Variable binding depth exceeds max-specpdl-size")"

event_jr Over a year ago

I don't. I'm using Emacs 24.1. Start emacs with emacs -Q. scroll-down isn't a good example because it's defined in C. But I still see the source fine.

cerhovice Over a year ago

Now I get "The C source file window.c is not available"

cerhovice Over a year ago

Strangely, in a blank new buffer, I do this: (symbol-function 'scroll-down) and then C-x C-e and all I get is: #<subr scroll-down> I am not sure what has gone wrong.

event_jr Over a year ago

Do you actually want to see the function definition or something else? You need to have the C sources installed if you do.

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