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From: Bakul Shah <bakul@iitbombay.org>
To: Computer Old Farts Followers <coff@tuhs.org>
Subject: [COFF] Re: Grep has gone overboard
Date: Sun, 29 May 2022 21:47:49 -0700	[thread overview]
Message-ID: <F83DB452-12EA-4EA4-8193-76B8FB5644D2@iitbombay.org> (raw)
In-Reply-To: <alpine.BSF.2.21.9999.2205301356510.35567@aneurin.horsfall.org>

You can write a program to generate all permutations and use that as your regexp.
For example abc maps to abc|acb|bac|bca|cab|cba. You can rearrange it as
a(bc|cb)|b(ac|ca)|c(ab|ba) to see how an n letter permutation is computed from
permutations of n-1 letters. I don’t think you can do better.

> On May 29, 2022, at 9:12 PM, Dave Horsfall <dave@horsfall.org> wrote:
> 
> I remember when the documentation was easy to read, but now...
> 
> I'm trying to find a regex i.e. as used by GREP to find all words in 
> "badugly" with each letter used only once and all are 7-letter words i.e. 
> they are all anagrams; perhaps it's my age (I hit 70 soon, after decades 
> in Unix) but I cannot seem to find a way to restrict the count i.e. each 
> letter used only once, but in any order.
> 
> I'll guess that it involves some obscure use of "{}*\" etc, which I've 
> never really grokked...
> 
> Ta muchly.
> 
> -- Dave

  reply	other threads:[~2022-05-30  4:48 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-30  4:12 [COFF] " Dave Horsfall
2022-05-30  4:47 ` Bakul Shah [this message]
2022-05-30  6:35   ` [COFF] " Michael Kjörling
2022-05-30  6:51     ` Bakul Shah
2022-05-30  8:26       ` Ralph Corderoy
2022-05-30  8:01     ` Ralph Corderoy
2022-05-30  8:16   ` Ralph Corderoy
2022-05-30  8:43     ` Bakul Shah
2022-05-30  9:19       ` Ralph Corderoy
2022-05-30  7:38 ` Ralph Corderoy
2022-05-30  7:44   ` Ralph Corderoy

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