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From: egt@hprnd.HP.COM (Eric Tausheck)
Newsgroups: comp.editors
Subject: Re: Re: A vi question
Message-ID: <3440004@hprnd.HP.COM>
Date: 23 Aug 90 21:06:06 GMT
References: <14420003@hp-lsd.COS.HP.COM>
Organization: HP Roseville Networks Division
Lines: 40

>
>   I had the need to do this kind of editing too until I learned about
>   col -b.
>
>   If what you started with had a bunch of back-spaces between the
>   letters too (as in an nroff or man output), the filter "col -b" does a
>   nice job of getting rid of all this junk for you.

I should have added that before I discovered the "col -b" filter, I used to
execute the following vi command to nroff output:

	:%s/.^H//g

(where the "^H" is entered with <ctrl>V<ctrl>H)



On a more interesting note...
>
>    :s/\(.\)\1\1\1/\1/g
>
>which works in "ed", but for some reason it didn't work in "vi".  So the
>next best thing (if you really must do it from within vi) is to use '!' to
>filter the relevant text through "sed".  E.g. for the whole file:
>
>    1G!Gsed 's/\(.\)\1\1\1/\1/g'

This is very powerful (of ed and sed).  Thanks for sharing this gem
regarding sed/ed.

A shame vi/ex doesn't implement it because it would (almost?) give vi/ex
true complete regular expression matching capabilities.

I'm very rusty on my formal language theory so for all I know this
(ability to self reference to patterns during regular expression
matching) may have given vi/ex full regular expression matching
capabilities - anyone out there care to speculate?

   Eric Tausheck			email: egt@hprnd.hp.com
   Hewlett Packard Co.