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Re: region-active-p
From: |
Stephen J. Turnbull |
Subject: |
Re: region-active-p |
Date: |
Fri, 26 Oct 2007 14:38:48 +0900 |
Richard Stallman writes:
> > When commands in XEmacs call [region-active-p], do they also test
> > for a nonempty region? Or do they operate on the region
> > when it is empty?
>
> Core commands defined in Lisp don't test (at least not within 3 lines,
> checked with grep -3), but they're generally wrappers for functions
> defined in C that do test (eg, the casefilling commands).
>
> I don't entirely understand the answer. Maybe I did not state the
> question clearly. When you say they "don't test", what precisely
> don't they test?
They don't test "for a nonempty region".
> Are you sayimg that they call `region-active-p' but do not test
> whether the region is nonempty?
Yes.
Specifically, the function that calls `region-active-p' does not.
However, in the cases I looked at, that function simply dispatches to
a more primitive function that acts on the region. The more primitive
function checks for non-empty in those cases. The typical idiom is
(defun fill-paragraph-or-region (arg)
"Fill the current region, if it's active; otherwise, fill the paragraph.
See `fill-paragraph' and `fill-region' for more information."
(interactive "*P")
(if (region-active-p)
(call-interactively 'fill-region)
(call-interactively 'fill-paragraph)))
`fill-region' *does* check that the region is nonempty before doing
any work.
- Re: region-active-p, (continued)
- Re: region-active-p, Stefan Monnier, 2007/10/21
- Re: region-active-p, Miles Bader, 2007/10/21
- Re: region-active-p, Andreas Röhler, 2007/10/21
- Re: region-active-p, Richard Stallman, 2007/10/23
- Re: region-active-p, Andreas Röhler, 2007/10/23
- Re: region-active-p, Richard Stallman, 2007/10/23
- Re: region-active-p, Andreas Röhler, 2007/10/24
- Re: region-active-p, Richard Stallman, 2007/10/24
- Re: region-active-p, Stephen J. Turnbull, 2007/10/24
- Re: region-active-p, Richard Stallman, 2007/10/25
- Re: region-active-p,
Stephen J. Turnbull <=
- Re: region-active-p, Andreas Röhler, 2007/10/26
- Re: region-active-p, Stephen J. Turnbull, 2007/10/26
- Re: region-active-p, Andreas Röhler, 2007/10/26
- Re: region-active-p, Stephen J. Turnbull, 2007/10/26
- Re: region-active-p, Richard Stallman, 2007/10/26
- Re: region-active-p, Stephen J. Turnbull, 2007/10/27
- Re: region-active-p, Miles Bader, 2007/10/27
- Re: region-active-p, Andreas Röhler, 2007/10/27
- Re: region-active-p, Stephen J. Turnbull, 2007/10/28
- Re: region-active-p, Miles Bader, 2007/10/28