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Re: Using variable names in a macro

From: Michael Heerdegen
Subject: Re: Using variable names in a macro
Date: Sun, 10 Dec 2017 18:32:52 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux)

Narendra Joshi <> writes:

> Can you share an example please? :)

If you want to go with anonymous functions, `letrec' is perfect here
(`cl-labels' would work as well and avoid the need to `funcall'):

#+begin_src emacs-lisp
;; -*- lexical-binding: t -*-

(defun my-do-when-idle (f g interval)
  "Call F when idle for INTERVAL seconds and then G when there is activity."
  (letrec ((run-timer-fun (lambda () (run-with-idle-timer
                                 interval nil
                                 (lambda ()
                                   (funcall f)
                                   (add-hook 'post-command-hook 
           (activity-fun (lambda ()
                           (remove-hook 'post-command-hook activity-fun)
                           (funcall g)
                           (funcall run-timer-fun))))
    (funcall run-timer-fun)))

I've changed the order in the `activity-fun' to run `remove-hook' first,
so that you get a sane behavior when running G gives an error.

A short test:

#+begin_src emacs-lisp
(my-do-when-idle (lambda () (message "%s" (current-time-string)))
                 (lambda () (message "Stopping timer"))


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