From: M Douglas McIlroy <m.douglas.mcilroy@dartmouth.edu>
To: tuhs@minnie.tuhs.org
Subject: [TUHS] [TUHS} Qed vs ed
Date: Sun, 31 Jan 2021 23:24:05 -0500 [thread overview]
Message-ID: <CAKH6PiXwMJ-LgF41nbQyK0oeKtBB3FCiOgnTJJLfpa_Bz_4Gkg@mail.gmail.com> (raw)
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> fairly early in PDP-11 development ed gained three features: & in the
> rhs of substitutions plus k and t commands. (I'm not sure about & ....
Oh, and backreferencing, which took regular expressions way up the
complexity hierarchy--into NP-complete territory were it not for the limit
of 9 backreferenced substrings. (Proof hint: reduce the knapsack problem to
an ed regex.)
Also g and s were generalized to allow escaped newlines.
I was indeed wrong about &. It was in v1.
Doug
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next reply other threads:[~2021-02-01 4:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-01 4:24 M Douglas McIlroy [this message]
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2021-01-31 15:26 M Douglas McIlroy
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