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From: letters@hotpop.com (Jari Aalto+mail.emacs)
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Subject: Difficult lisp macro question (related to gnus-group.el)
Date: Mon, 18 Aug 2003 18:23:27 +0300
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I noticed that the `gnus-group-quick-select-group' function M-RET in
Group buffer only sets few hooks to nil:

  (let (gnus-visual
	gnus-score-find-score-files-function
	gnus-home-score-file
	gnus-apply-kill-hook
	gnus-summary-expunge-below)

I'm in a process of making and proposing a patch to allow user to
define what hooks he want to be set to `nil' instead of the hard coded
version. However, I don't seem to be able to solve how to contruct `let' 
dynamically from a variable, say `hook-list'. That is:

- Given a defvar hook-list (list of hooks to disable)
- The function definition's let should include all those
  hooks defined in `hook-list' locally set to nil.

  (let (gnus-visual     ;;  User given hook 1
        ...             ;;  User given hook 2
        ...             ;;  ...
        )

If this is not clear, Example below hopefully demontrates the
intention. I have a problem figuring out how I make the
`my-let-transform' to contruct that `let' around the BODY which
includes all `list' variables set to nil.

    (let ((list '(a
                  b
                  c)))

      (setq a 1)

      (defmacro my-let-transform (list &rest body)
        (` 
         (progn
           (,@ body))))

      (defun my-test ()
        (my-let-transform list
                          (message "A: %d" a)))

      (my-test))


=> The result of `my-test' should show after macroexpand:

      (defun my-test ()
        (let (a
              b
              c)
          (message "A: %d" a)))

Any ideas?
Jari