Why do regexes use `$` and `^` as line anchors? (opens in new tab)

(buttondown.email)

32 pointsmanuw2y ago14 comments

14 comments

> So there you have it, an explanation for the regex anchors that kinda makes sense.

That’s not an explanation, it’s speculation. The whole article was guess work and you picked something that sounded plausible. Ken Thompson is alive, why not ask and confirm? Then you could say you have an explanation.

bitshiftfaced2y ago

Explanations and speculation: are they mutually exclusive? I'd say an answer from Ken Thompson would be a definitive explanation that might disprove the author's explanation, but that doesn't mean it's not an explanation.

latexr1y ago

> Explanations and speculation: are they mutually exclusive?

Yes. You only need to speculate when you don’t have a firm explanation.

> disprove the author's explanation

Speculation is “the forming of a theory or conjecture without firm evidence”, which is what the author is doing. They’re not explaining, they’re guessing at a reason.

sethammons2y ago

Ken is still around; did the author reach out and ask? Could be a similar story to Rob Pike and the Go date format: he didn't think about it and just picked the first thing that came to mind.

benrapscallion2y ago

The article devolves from fact to fiction/guesswork rather quickly.

lesquivemeau2y ago

This always made sense to me because they are next to each other on an AZERTY keyboard: tab,A,Z,E,R,T,Y,U,I,O,P,^,$,return

agumonkey2y ago

Another roman car like effect.

Lex-20082y ago

Not sure about $ sign, but ^ probably comes from ADM-3A: https://en.wikipedia.org/wiki/ADM-3A#Legacy

And here is a photo of its keyboard: https://twitter.com/toresbe/status/1756800589340549609/photo...

em5002y ago

Per the article, these anchors appear in Ken Thompson's port of the QED text editor which dates back to 1970, years before even the ADM-1 terminal.

sys_647382y ago

They're because that's what Bill Joy used in vi back in 1979 to move to the beginning and end of a line. It made sense to use them for regex too.

em5002y ago

Per the article, these anchors appear in Ken Thompson's port of the QED text editor, which dates back to 1970.

demondemidi2y ago

The article is all speculation and not fact. Sorry OP but this is just garbage content.

JSR_FDED2y ago

This article should be considered the $ word on this topic.

j / k navigate · click thread line to collapse

14 comments

latexr2y ago

> So there you have it, an explanation for the regex anchors that kinda makes sense.

bitshiftfaced2y ago

latexr1y ago

> Explanations and speculation: are they mutually exclusive?

Yes. You only need to speculate when you don’t have a firm explanation.

> disprove the author's explanation

Speculation is “the forming of a theory or conjecture without firm evidence”, which is what the author is doing. They’re not explaining, they’re guessing at a reason.

sethammons2y ago

Ken is still around; did the author reach out and ask? Could be a similar story to Rob Pike and the Go date format: he didn't think about it and just picked the first thing that came to mind.

benrapscallion2y ago

The article devolves from fact to fiction/guesswork rather quickly.

lesquivemeau2y ago

This always made sense to me because they are next to each other on an AZERTY keyboard: tab,A,Z,E,R,T,Y,U,I,O,P,^,$,return

agumonkey2y ago

Another roman car like effect.

Lex-20082y ago

Not sure about $ sign, but ^ probably comes from ADM-3A: https://en.wikipedia.org/wiki/ADM-3A#Legacy

And here is a photo of its keyboard: https://twitter.com/toresbe/status/1756800589340549609/photo...

em5002y ago

Per the article, these anchors appear in Ken Thompson's port of the QED text editor which dates back to 1970, years before even the ADM-1 terminal.

sys_647382y ago

They're because that's what Bill Joy used in vi back in 1979 to move to the beginning and end of a line. It made sense to use them for regex too.

em5002y ago

Per the article, these anchors appear in Ken Thompson's port of the QED text editor, which dates back to 1970.

demondemidi2y ago

The article is all speculation and not fact. Sorry OP but this is just garbage content.

JSR_FDED2y ago

This article should be considered the $ word on this topic.

j / k navigate · click thread line to collapse