Re: Dynamically constructing advice behaves strangely

[Michael Heerdegen <michael_heerdegen@web.de>]

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!).


Michael.