From: markus schnalke <meillo@marmaro.de> To: tuhs@minnie.tuhs.org Subject: [TUHS] RegExp decision for meta characters: Circumflex Date: Fri, 17 Sep 2021 10:52:00 +0200 [thread overview] Message-ID: <1mR9bE-8RG-00@marmaro.de> (raw) Hoi, I'm interested in the early design decisions for meta characters in REs, mainly regarding Ken's RE implementation in ed. Two questions: 1) Circumflex As far as I see, the circumflex (^) is the only meta character that has two different special meanings in REs: First being the beginning of line anchor and second inverting a character class. Why was it chosen for the second one? Why not the exclamation mark in that case? (Sure, C didn't exist by then, but the bang probably was used to negate in other languages of the time, I think.) 2) Symbol for the end of line anchor What is the reason that the beginning of line and end of line anchors are different symbols? Is there a reason why not only one symbol, say the circumflex, was chosen to represent both? I currently see no disadvantages of such a design. (Circumflexes aren't likely to end lines of text, neither.) I would appreciate if you could help me understand these design decisions better. Maybe there existed RE notations that were simply copied ... meillo
next reply other threads:[~2021-09-17 8:59 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-09-17 8:52 markus schnalke [this message] 2021-09-17 9:32 ` Rob Pike 2021-09-17 9:32 ` Rob Pike 2021-09-17 10:10 ` markus schnalke 2021-09-17 16:40 Douglas McIlroy 2021-09-17 20:40 ` Chris Torek 2021-09-18 1:03 ` Greg 'groggy' Lehey 2021-09-18 1:23 ` Bakul Shah
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