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Why Do Regexes Use `$` and `^` as Line Anchors?

posted by janrinok on Wednesday March 27 2024, @08:12PM   Printer-friendly
from the I-didn't-know-that-... dept.

owl writes:

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?

Original Submission

 
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  • (Score: 3, Touché) by owl on Thursday March 28 2024, @07:31PM

    by owl (15206) on Thursday March 28 2024, @07:31PM (#1350746)

    Then narrow your viewing window, and suddenly, you get "less wide" text layouts.

    The only reason you get very wide layouts is you have your browser window sized to be "very wide". I.e., the problem is completely under your control.

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