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From: Douglas McIlroy <douglas.mcilroy@dartmouth.edu>
To: TUHS main list <tuhs@minnie.tuhs.org>
Subject: [TUHS] RegExp decision for meta characters: Circumflex
Date: Fri, 17 Sep 2021 12:40:43 -0400	[thread overview]
Message-ID: <CAKH6PiUdxuOV3ySkD8m7W+O7k_Yh12XdtHnOkdAJFB4xfAiEig@mail.gmail.com> (raw)

> Maybe there existed RE notations that were simply copied ...

Ed was derived from Ken's earlier qed. Qed's descendant in Multics was
described in a 1969 GE document:
http://www.bitsavers.org/pdf/honeywell/multics/swenson/6906.multics-condensed-guide.pdf.
Unfortunately it describes regular expressions only sketchily by
example. However, alternation, symbolized by | with grouping by
parentheses, was supported in qed, whereas alternation was omitted
from ed. The GE document does not mention character classes; an
example shows how to use alternation for the same purpose.
Beginning-of-line is specified by a logical-negation symbol. In
apparent contradiction, the v1 manual says the meanings of [ and ^ are
the same in ed and (an unspecified version of) qed. My guess about the
discrepancies is no better than yours.

(I am amused by the title "condensed guide" for a manual in which each
qed request gets a full page of explanation. It exemplifies how Unix
split from Multics in matters of taste.)

Doug

             reply	other threads:[~2021-09-17 16:41 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-17 16:40 Douglas McIlroy [this message]
2021-09-17 20:40 ` Chris Torek
2021-09-18  1:03   ` Greg 'groggy' Lehey
2021-09-18  1:23     ` Bakul Shah
  -- strict thread matches above, loose matches on Subject: below --
2021-09-17  8:52 markus schnalke
2021-09-17  9:32 ` Rob Pike
2021-09-17  9:32   ` Rob Pike
2021-09-17 10:10   ` markus schnalke

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