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Re: How can function know its own name?
From: |
Jean Louis |
Subject: |
Re: How can function know its own name? |
Date: |
Sun, 26 Jun 2022 11:08:26 +0300 |
User-agent: |
Mutt/+ () (2022-05-21) |
* tomas@tuxteam.de <tomas@tuxteam.de> [2022-06-26 08:46]:
> On Sat, Jun 25, 2022 at 11:21:20PM +0300, Jean Louis wrote:
> >
> > I would like to invoke logging for specific functions automatically,
> > without specifying what to log, and my function should know which
> > function invoked it.
>
> This is not completely trivial. In Lisp, a function has no name.
> It is a first-class object which can be bound to (the function
> slot) of a symbol (or to that of two, three... symbols).
>
> It's like the value 42. Many variables can be bound to that. Or
> none.
>
> What name has (lambda (x) (if (= (mod x 2) 1) (+ (* 3 x) 1) (/ x 2)))?
>
> None (yet?).
>
> Try this:
>
> (setf (symbol-function 'foo) (lambda (x) (+ x 1)))
>
> Now:
>
> (foo 13)
>
> => 14
>
> So that function that adds one to its argument is now arguably
> called foo. But:
>
> (setf (symbol-function 'bar) (symbol-function 'foo))
>
> Then:
>
> (bar 14)
>
> => 15
>
> ...it can be called bar at the same time. Well, I can be called
> two names too, can't I?
>
> See 13.3 "Naming a function" and 9.1 "Symbol Components" in our
> beloved Emacs Lisp manual for all the gory details.
>
> Now to the interesting question: how do debuggers pull it off?
OK.
Maybe one way to give function a capacity to find out its name, the
name of the called function from inside of itself could be to call it
in a wrapper which sets global variable to be symbol of the function.
(defvar rcd-called-function)
(defun rcd-call-function (function &rest args)
(setq rcd-called-function function)
(apply function args)
(setq rcd-called-function nil))
(defun my-fun ()
(message "My function name is: %s" rcd-called-function))
(rcd-call-function 'my-fun) ⇒ nil
--
Jean
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