RetroBBS - comp.lang.tcl - possible "regsub/regexp" bug

possible "regsub/regexp" bug

<t9job7$1oadh$1@dont-email.me>

https://www.rocksolidbbs.com/devel/article-flat.php?id=19608&group=comp.lang.tcl#19608

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From: aotto1968@t-online.de (aotto1968)
Newsgroups: comp.lang.tcl
Subject: possible "regsub/regexp" bug
Date: Thu, 30 Jun 2022 10:53:59 +0200
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by: aotto1968 - Thu, 30 Jun 2022 08:53 UTC

Hi,

I have the following regexp:

> "(?!$)([A-Z][a-z]+)(?!$)"

and I want to match

> "MkObjectLogC"

into:

> "(?:Mk)?(?:Object)?(?:Log)?C"

using the code

> set match "MkObjectLogC"
> while {[regsub {(?!$)([A-Z][a-z]+)(?!$)} $match {(?:\1)?} match]} {}

but the solution is:

> "(?:Mk)?(?:(?:(?:(?:(?:Ob)?j)?e)?c)?t)?(?:(?:Lo)?g)?C"

the online regexp is ok:

> https://regex101.com/r/cWJrDK/1

mfg

Re: possible "regsub/regexp" bug

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https://www.rocksolidbbs.com/devel/article-flat.php?id=19609&group=comp.lang.tcl#19609

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Date: Thu, 30 Jun 2022 12:40:39 +0200
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References: <t9job7$1oadh$1@dont-email.me>
From: nospam@wanadoo.nl (Schelte)
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by: Schelte - Thu, 30 Jun 2022 10:40 UTC

On 30/06/2022 10:53, aotto1968 wrote:
> using the code
>
> > set match "MkObjectLogC"
> > while {[regsub {(?!$)([A-Z][a-z]+)(?!$)} $match {(?:\1)?} match]} {}
>
> but the solution is:
>
> > "(?:Mk)?(?:(?:(?:(?:(?:Ob)?j)?e)?c)?t)?(?:(?:Lo)?g)?C"
>
> the online regexp is ok:
>
That's because you repeatedly reprocess the result of the previous
substitution. The online regexp does the processing in one go. If you do
the same with regsub, you get the requested result:

regsub -all {(?!$)([A-Z][a-z]+)(?!$)} $match {(?:\1)?} match

Schelte.

RAM wasn't built in a day.

devel / comp.lang.tcl / possible "regsub/regexp" bug

Subject	Author
possible "regsub/regexp" bug	aotto1968
Re: possible "regsub/regexp" bug	Schelte