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From: rap@peck.ardent.com (Rob Peck)
Newsgroups: comp.sys.amiga
Subject: Re: Editor
Message-ID: <8720@ardent.UUCP>
Date: 16 Oct 89 18:00:58 GMT
References: <8Z=r0qy00WE501I2hz@andrew.cmu.edu> <857@lyra.stsci.edu> <11876@watcgl.waterloo.edu> <493@sagpd1.UUCP>
Sender: news@ardent.UUCP
Reply-To: rap@peck.ardent.com (Rob Peck)
Organization: Ardent Computer Corp., Sunnyvale, CA
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In article <493@sagpd1.UUCP> monty@sagpd1.UUCP (Monty Saine) writes:
>In article <11876@watcgl.waterloo.edu> bmacintyre@watcgl.waterloo.edu (Blair MacIntyre) writes:
>>In article <857@lyra.stsci.edu> levay@stsci.EDU (Zoltan Levay) writes:
>>>In article <8Z=r0qy00WE501I2hz@andrew.cmu.edu>, ms0p+@andrew.cmu.edu (Michael Gordon Shapiro) writes:
>>
>>The undo in VI is only one level.  Useful, but hardly noteworthy.  To be truely
>                    ^^^^^^^^^^^^^
>    Are you talking about Stevie here or "generic" vi's. The vi on our system
>    supports I believe 10 (maybe 36, I can't remember now and I don't have the
>    manual around) levels of undo's. In other words you can recall the
>    last ten deletions in any order. I will give you that it is not a simple
>    single key stroke but the  facility does exist. It will also undo undo's.
>
>    Monty Saine

The documentation that most manuals provide for vi is sadly lacking
in the area of talking about the buffers.  Below is an extract that
describes the use of numbered buffers in vi.  Yes, vi has up to
a ten level undo (restoring deletes, that is).  Here is a description
showing how to take advantage of that.

======================================================================

Copyright 1989, Ardent Computer Corp, All Rights Reserved

	Extracted from "Programmer's Guide"
		Author: Rob Peck



Using Numbered Buffers

Numbered buffers hold the 9 most recently deleted blocks of text
and operate as a pushdown stack, along with the unnamed buffer.
As an example, if there is a deleted line currently in the unnamed 
buffer, and another line is deleted, then the first line is pushed
into numbered buffer 1, and the unnamed buffer now has the most
recently deleted line or block of text.  The former contents of
buffer 1 are pushed into buffer 2, the contents
of 2 goes to 3 and so on, for a total of 9 numbered buffers.

To reinsert any blocks of text from these buffers, you
use the put command (p or P) as follows.  Assume
you want to restore something that you deleted three deletes ago.
The unnamed buffer contains the most recent deletion, Buffer 1
the second most recent, and buffer 2 contains that
third most recent deletion, the one you wish to restore.
Move the cursor to the postion at which to insert the text and type:

	"2p

The double-quote character says that you are referring to a buffer.
The 2 is the number of the buffer that you are using.   Finally
the p is the command to put the contents into the edit buffer.

The contents of all of the numbered buffers remains the same until the
next delete happens, even across edit-file boundaries.

An interesting trick is possible using vi's undo command.  Lets say
you know that what you want to insert somewhere was deleted recently
(within the last 9 block deletes), but you are not quite certain
which one of those deletes it was.  You can use the repeat command (.)
feature, along with undo, to view the contents of the numbered buffers
sequentially as shown in the example here.
First, issue a command that inserts the first of
these numbered buffers:

	"1p

If this is not the one you want, issue the command

	u.

This has the same effect as though you had typed "2p.
Internal to vi, the effect is to increment the buffer
number, undo your original put, and try it again with
the next numbered buffer.

If you wish to try this command, create a text file that
contains the following lines:

Here is where to put the stuff
8th deleted line
The bottom line

Place the cursor somewhere in the first line, then enter
the following command characters:

	dd.........

(dd followed by 8 periods)  This fills all 9 delete buffers, one
with each sentence.

Now position the cursor in the line containing the word
'Here', and issue the command:

	"1p

It brings back the line 1st deleted line.  Now issue the
command:

	u.

Each time you issue this command, the current deleted line
disappears and is replaced by the next one in sequence.
Whatever was the deleted block, in each case, appears in 
response to this command.  The deleted block might contain a
word, a line, or a large block of text.
The only disadvantage to using the double-quote commands is that
there is no user feedback provided until you complete the command.
However, you can always use undo if you discover you have made a mistake.

=========================================================================
Rob Peck