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posted by janrinok on Wednesday March 27, @08:12PM   Printer-friendly
from the I-didn't-know-that-... dept.

https://buttondown.email/hillelwayne/archive/why-do-regexes-use-and-as-line-anchors/

Last week I fell into a bit of a rabbit hole: why do regular expressions use $ and ^ as line anchors?1

This talk brings up that they first appeared in Ken Thompson's port of the QED text editor. In his manual he writes: b) "^" is a regular expression which matches character at the beginning of a line.

c) "$" is a regular expression which matches character before the character (usually at the end of a line)

QED was the precursor to ed, which was instrumental in popularizing regexes, so a lot of its design choices stuck.

Okay, but then why did Ken Thompson choose those characters?


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  • (Score: 2) by VLM on Friday March 29, @07:39PM (1 child)

    by VLM (445) on Friday March 29, @07:39PM (#1350900)

    it's the key left of the 1 key

    OK fine I give up what is your keyboard? Its not an AZERTY thing... You remap the key for some reason?

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  • (Score: 3, Informative) by cereal_burpist on Saturday March 30, @03:54AM

    by cereal_burpist (35552) on Saturday March 30, @03:54AM (#1350966)
    Looks like QWERTZ [wikipedia.org]