Regex Rules

Regex Rules

[jgart]

Hi,

Where can I find all the regex rules for this style of regex?

"\\$\\{PG_SHAREDIR\\}/extension"

That's a snippet I took at random from guix/

all best,

jgart

Re: Regex Rules

[Julien Lepiller]

\\ is for inputing a single \ (it needs to be etcaped in guile strings). Then, the rest is a Guile regexp, wgicg you can liarn about at https://www.gnu.org/software/guile/manual/html_node/Regular-Expressions.html.

The manual says it's POSIX regexp, whatever that means :)

Le 10 novembre 2022 03:04:12 GMT+01:00, jgart <jgart@dismail.de> a écrit :
>Hi,
>
>Where can I find all the regex rules for this style of regex?
>
>"\\$\\{PG_SHAREDIR\\}/extension"
>
>That's a snippet I took at random from guix/
>
>all best,
>
>jgart
>
>

Re: Regex Rules

[jgart]

On Thu, 10 Nov 2022 07:37:00 +0100 Julien Lepiller <julien@lepiller.eu> wrote:
> \\ is for inputing a single \ (it needs to be etcaped in guile strings). Then, the rest is a Guile regexp, wgicg you can liarn about at https://www.gnu.org/software/guile/manual/html_node/Regular-Expressions.html.
> 
> The manual says it's POSIX regexp, whatever that means :)

I'm familiar with posix regex from using vis:

https://github.com/martanne/vis

But, iirc vis regex are different from Guile's

I might be wrong on that.

I'll have to check the parity between the two

thanks,

jgart

Re: Regex Rules

[Tobias Geerinckx-Rice]

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I recommend starting with the regex(7) man page, before comparing 
any implementation to another.

> But, iirc vis regex are different from Guile's
> I might be wrong on that.

‘By default, Guile supports POSIX extended regular expressions.’ — 
(guile)Regexp Functions

‘[vis] uses what POSIX refers to as “Extended Regular 
Expressions”’ — vis(1)

Kind regards,

T G-R

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Re: Regex Rules

[Felix Lechner via]

Hi,

On Thu, Nov 10, 2022 at 11:39 AM Tobias Geerinckx-Rice <me@tobias.gr> wrote:
>
> ‘By default, Guile supports POSIX extended regular expressions.’ —

Yes, the word "extended" is often omitted. A good summary is here. [1]

POSIX adopted some, but not all, of the Perl Compatible Regular
Expressions (PCRE), which are more powerful but older. From the 'grep'
manual page (see the -E switch): "In basic regular expressions the
meta-characters ?, +, {, |, (, and ) lose their special meaning".

Kind regards
Felix Lechner

[1] https://en.wikibooks.org/wiki/Regular_Expressions/POSIX-Extended_Regular_Expressions

Re: Regex Rules

[Christopher Rodriguez]

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>> Where can I find all the regex rules for this style of regex?
> \\ is for inputing a single \ (it needs to be etcaped in guile
> strings). Then, the rest is a Guile regexp, wgicg you can liarn about
> at
> https://www.gnu.org/software/guile/manual/html_node/Regular-Expressions.html.
>
> The manual says it's POSIX regexp, whatever that means :)

My $0.02:

When I dove into it a while ago, I was able to make progress once I
realized Regexps in Guile conform to POSIX Extended Regular Expressions
[1], with the added caveat of having to escape them as strings [2].

[1]: https://www.regular-expressions.info/posix.html
[2]: https://www.gnu.org/software/guile/manual/html_node/String-Syntax.html

-- 
Christopher Rodriguez
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