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Re: Programmatically creating functions


From: Joost Diepenmaat
Subject: Re: Programmatically creating functions
Date: Tue, 21 Oct 2008 20:34:07 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.60 (gnu/linux)

Ian Eure <address@hidden> writes:

> So, I have a list of symbols:
>
> '(foo bar baz)
>
> I want to iterate over the list and create a function from each which
> does something like this:
>
> (defun call-foo ()
>   (interactive)
>   (invoke-stuff 'foo)
>
> How can I accomplish this? I can't figure out how to create the
> function. I've tried a number of approaches, but have not met with
> success.
>
>  - eval'ing the defun. Returns a function symbol, but I can't call
> it. Maybe it's only created within the scope of the (eval) and not
> callable from outside?
>
>  - Creating a symbol and using fset to assign a lambda to it's
> function cell. It sort of works, but I'm unclear on how to pass a
> variable function name to defun, nor am I clear on how I can make sure
> it calls invoke-stuff with the right symbol.

I'm not /quite/ sure where you've got problems, but in this case elisp's
lack of closures hurts. IMHO the simplest way to get what you want is to
use a macro:

(defmacro make-caller-macro (symbol) 
  `(defun ,(intern (concat "call-" (symbol-name symbol))) () 
     (,symbol)))

But that won't evaluate the argument, so you'd more or less have to use
eval as well:

(dolist (s '(foo bar)) (eval `(make-caller-macro ,s)))

-- 
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/


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