Re: Dynamically constructing advice behaves strangely

[Marcin Borkowski <mbork@mbork.pl>]

On 2016-02-14, at 16:44, Michael Heerdegen <michael_heerdegen@web.de> wrote:

> Marcin Borkowski <mbork@mbork.pl> writes:
>
>> (defun add-constructed-advice (fun)
>>   "Add a constructed advice to function foo."
>>   (let* ((fun-name (symbol-name fun))
>> 	 (length-sym
>> 	  (make-symbol (concat "length-of-" fun-name)))
>> 	 (piece-of-advice-sym
>> 	  (make-symbol (concat "advice-for-" fun-name)))
>> 	 (piece-of-advice (lambda (orig-fun &rest args)
>> 			    (apply orig-fun args)
>> 			    (message "This function's name had length %s."
>> 				     (symbol-value length-sym)))))
>
> Also, `length-sym' doesn't have to be an uninterned symbol here.  You
> use lexical-binding anyway (by referring to the value of the (interned!)
> symbol named "length-sym".  You don't even have to use a symbol with a
> unique name.  Just use a simple (lexical) variable for the length,
> e.g. `advice-length', and
>
> (message "This function's name had length %s." advice-length)
>
> etc. (your piece of advice is a closure!).

I know, and in fact I'm making use of lexical binding in my "real"
code.  This was just a trimmed-down version for the sake of asking here.

> Michael.

Best,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University