From: Luc Teirlinck <teirllm@dms.auburn.edu>
Subject: flush-lines and keep-lines
Date: Wed, 15 Jun 2005 22:17:48 -0500 (CDT) [thread overview]
Message-ID: <200506160317.j5G3Hmp26222@raven.dms.auburn.edu> (raw)
There are some inconsistencies between flush-lines and keep-lines, if
they operate on a region that contains partial lines.
If point is not at the beginning of a line, `flush-lines' gets rid of
the line point is on if and only if the part of the line _after_ point
contains a match for the regexp. `keep-lines' unconditionally keeps
that line. This difference in philosophy might not be too bad and
could just be documented.
With transient mark mode enabled and an active region, a partial line
at the beginning of the region is treated as above. Might again not
be too bad. `flush-lines' erases a partial line at the end of the
region if and only if the part _inside the region_ contains a match for
regexp, thereby being consistent with its own behavior for the line at
the beginning of the region. But the behavior of `keep-lines' there
seems very unexpected.
Take a buffer with the following three lines:
12
34
56
If the region starts at 2 and ends at 5 (both _inclusive_)
M-x keep-lines RET 7 RET results in:
12
6
The last line got _partially_ erased. The docs seem to suggest that
keep-lines should keep or erase entire lines, not parts of them, even
in the presence of partial lines.
To make the behavior of `keep-lines' symmetric at both ends of the
region, the last line should be unconditionally kept in its entirety.
Maybe the difference with flush-lines could then be explained by the
principle: If you are not sure, just by looking at the region,
whether to erase or keep, then keep the line.
You can never be sure by looking only at part of a line that the
entire line does _not_ contain a match, so keep-lines always needs to
keep all partial lines. But if the part you are seeing contains a
match, you _know_ that flush-lines needs to erase it.
Sincerely,
Luc.
next reply other threads:[~2005-06-16 3:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-16 3:17 Luc Teirlinck [this message]
2005-06-16 16:24 ` flush-lines and keep-lines Richard Stallman
2005-06-17 3:00 ` Luc Teirlinck
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