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I'm using this code on Xubuntu (emacs 24.5.1) but it throw error on windows (emacs 25.0.50.1 64bit)

(defun ignore-error-wrapper (fn)
  "Funtion return new function that ignore errors.
   The function wraps a function with `ignore-errors' macro."
  (lexical-let ((fn fn))
    (lambda ()
      (interactive)
      (ignore-errors
        (funcall fn)))))

(global-set-key [s-left] (ignore-error-wrapper 'windmove-left))
(global-set-key [s-right] (ignore-error-wrapper 'windmove-right))
(global-set-key [s-up] (ignore-error-wrapper 'windmove-up))
(global-set-key [s-down] (ignore-error-wrapper 'windmove-down))
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  • Please include some description of the error that is signaled. My crystal ball says that the problem is that you use lexical-let without first requiring cl (which is the package that exports lexical-let).
    – Stefan
    Commented Dec 9, 2015 at 13:12
  • @Stefan FWIW the error (void-function lexical-let) was mentioned in the title of the question. (But I do think it is very confusing.)
    – YoungFrog
    Commented Dec 10, 2015 at 10:31

1 Answer 1

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lexical-let is defined in cl.el. You can (eval-when-compile (require 'cl)) to fix the problem. This is mostly equivalent to (require 'cl) but is more efficient when you byte-compile your code (see Drew's comment below).

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  • 2
    cl-lib is preferred to cl. To quote the CL manual: "New code should use cl-lib rather than cl." Ref: gnu.org/software/emacs/manual/html_node/cl/…
    – bmag
    Commented Dec 9, 2015 at 11:37
  • 3
    But cl-lib doesn't define lexical-let, so it's a bit less interesting for the problem at hand. I think the preferred way would be to rewrite the code with lexical-binding turned on.
    – YoungFrog
    Commented Dec 9, 2015 at 11:40
  • You are correct. I assumed that cl-lib provided lexical-let, but I was wrong.
    – bmag
    Commented Dec 9, 2015 at 11:46
  • 3
    Nope. You do not need to (and should not, since you do not need to), require cl.el at runtime. lexical-let is a macro (defined in cl.el), so what you should do is (eval-when-compile (require 'cl)).
    – Drew
    Commented Dec 9, 2015 at 14:40

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