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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 owl on Thursday March 28, @07:29PM (1 child)

    by owl (15206) on Thursday March 28, @07:29PM (#1350745)

    CSS is great, but should even that be necessary? Reflowing of text to fit window sizes is a core feature of plain old HTML. No more reliance on CR/LF for that.

    Because by far too many designers feel some hugely irrational need to control the layout to a level far more strict than "let html lay out the data based upon the viewport width".

    Note that most of these designers are those from the "publishing" environment where positioning text in this corner of a page, and a highlight image over in this other spot, in order to leave room in three other places for three ad slots, was what they were trained to do.

    I.e., they never even consider just letting the HTML lay itself out natively. They need to control where it goes, to the pixel, or they feel they have failed.

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  • (Score: 2) by krishnoid on Thursday March 28, @09:21PM

    by krishnoid (1156) on Thursday March 28, @09:21PM (#1350758)

    Designers are probably trained for traditional print media, and something that describes layouts and floats using declarative and markup languages is probably going to require a GUI for them to be able to do their thing. They're not coders, after all.