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bug#21072: 24.5; inconsistent behaviour of `C-M-h (mark-defun)' in Emacs
From: |
Drew Adams |
Subject: |
bug#21072: 24.5; inconsistent behaviour of `C-M-h (mark-defun)' in Emacs Lisp |
Date: |
Wed, 2 Nov 2016 11:25:20 -0700 (PDT) |
> Well, both these behaviors are manifestations of the same bug.
> Below is the corrected version. (And below that a question.)
The test cases I mentioned work now. Thx. I didn't try anything
beyond those cases. Hopefully others will test a bit more.
> > 6. Interactively, I would rather see repeated use of `C-M-h',
> > after an initial use of `C-M-h' with a negative prefix arg
> > (e.g. `M-- C-M-h'), continue to select defuns backward.
> > IOW, not need to use `M--' explicitly for each `C-M-h'.
> >
> > You can just hold down `C-M-h', to select multiple defuns
> > forward. I would like to be able to do the same thing,
> > but backward, by using `M-- C-M-h C-M-h C-M-h C-M-h...'
> > (just hold down the chord).
> >
> > If you do that, then a negative prefix arg should not mean
> > backward; it should just mean change direction (backward if
> > previous command was not `mark-defun').
>
> Just to be sure: you mean only the minus sign as argument, not
> a negative number?
No, not really. But use your own judgment, I guess.
This is the kind of behavior I had in mind. This is for
`transpose-sexps', but it shows the behavior. _Any_ negative
arg flips the direction. At the outset, a negative arg means
move backward. The absolute value of ARG is the number of
sexps to move over.
(defun reversible-transpose-sexps (arg)
"Reversible and repeatable `transpose-sexps'.
Like `transpose-sexps', but:
1. Leaves point after the moved sexp.
2. When repeated, a negative prefix arg flips the direction."
(interactive "p")
(when (eq last-command 'rev-transp-sexps-back) (setq arg (- arg)))
(transpose-sexps arg)
(unless (natnump arg)
(backward-sexp (abs arg))
(skip-syntax-backward " .")
(setq this-command 'rev-transp-sexps-back)))
(If you happen to try this with ARG=0, be aware that what you
see is just the peculiar `transpose-sexps' behavior for ARG=0.
This is not related to the code here.)
> I'm also wondering whether to allow that for
> non-interactive use, too: I'm pretty sure nobody would want to call
> (mark-defun '-) from Lisp code, and it might make testing slightly
> easier.
I think the behavior should be the same. But see above. The
arg passed should be numeric (positive, zero, or negative), IMO.