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From: Thien-Thi Nguyen <ttn@gnuvola.org>
Newsgroups: gmane.emacs.devel
Subject: Re: emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...)))
Date: Tue, 04 Jan 2011 18:00:57 +0100
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() Stefan Monnier <monnier@iro.umontreal.ca>
() Sun, 02 Jan 2011 21:19:44 -0500

   The only problem I can see with it is that it relies on a
   function call, which is a slow operation in the current Elisp
   implementation.

Perhaps the compiler can optimize

  (EXPR =3D> (lambda (VAR) BODY))

to be

  (let ((VAR EXPR))
    (when VAR
      ;; book-keeping to mark =E2=80=98cond=E2=80=99 success,
      ;; to preclude next clause, here.
      BODY))

?