Re: Programmatically creating functions

[Andreas Politz <politza@fh-trier.de>]

Joost Diepenmaat wrote:
> Ian Eure <ian@digg.com> 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)))
> 


Does this work ? (in general)

(defun make-fun (name)
   (fset (intern (format "call-%s" name))
	`(lambda nil
	   ,(format "call-%s is a very good function." name)
	   (interactive)
	   (message "I was once %s" (quote ,name)))))

(mapcar 'make-fun '(foo bar baz))
(describe-function 'call-baz)
(call-bar)

-ap