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From: gast@lanai.cs.ucla.edu (David Gast)
Newsgroups: comp.editors
Subject: Re: vi mapping difficulty
Message-ID: <1991Mar13.084943.934@cs.ucla.edu>
Date: 13 Mar 91 08:49:43 GMT
References: <1991Mar08.205940.11108@vpnet.chi.il.us>
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In article <1991Mar08.205940.11108@vpnet.chi.il.us> dattier@vpnet.chi.il.us (David W. Tamkin) writes:
>I'm having a problem with a key mapping in vi.  If anyone can help, I'd
>surely appreciate it.

>I want to clear out any lines that don't have text on them.  The purpose is
>to separate paragraphs in quoted text.  So I have this in my .exrc:

	map ^X :v/[0-9A-Za-z]/s/.*//^M

I use EXINIT instead of .exrc.  One line from that EXINIT say:

		map #4 mz:%s/[	 ][	 ]*$//^M`z

where there is a tab and a space between every [ and ] pair.  The mz and
`z are to return me the same place in the file.
 
This macro is not exactly the same as yours.  First, it deletes trailing
white space; secondly, it defines text to be any printable character while
yours defines text to be only alphanumeric text.  You can easily make the
change if you really desire your semantics.  In particular, I use mine
to make d} work (paragraphs are not recognized where a line contains tabs
and/or blanks) and to get rid of trailing white space; however, in re-reading
your posting, I think you want to make a paragraph break whenever rn (or
some other news server) has inserted a > (or related character) at the
beginning of a blank line so that a line that only contains characters
like "<>=" is made empty.  Is that what you mean by quoted text?  Thus,
you could use as the left hand side of the s command:

	^[^a-zA-Z0-9][^a-zA-Z0-9]*$

where all the ^s are literal.  Please note, however, while, I think, the
the change immediately above describes what you wrote, it may not be what
you want.  For example, any lines that contain only a { or } (from a C
program perhaps) will also be deleted.  You *may* want to change only
those lines beginning with > or only those lines containing >*.

My macro is superior in terms of speed (only an issue for large files)
because s is much faster than v/g.  If you don't believe it, try two
identical command on /usr/dict/words and notice the difference in time.
That is, you should only use v or g when you want to do something that
s alone cannot do like delete the line or change a different line.

>If I've just read the file into the buffer and made no changes yet, it works.
>Otherwise, one or two occurrences of the pattern get replaced and the
>operation stops with "Can't undo in global" -- so who asked for an undo?

I have never had this happen with my macro and I don't see why you are
having difficulties.  I did not try to investigate either.

David