GNU bug report logs - #2816
regexp-opt: does not optimize 'Abc' and 'abc'

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Package: emacs; Severity: wishlist; Reported by: Jari Aalto <jari.aalto@HIDDEN>; Done: Stefan Kangas <stefankangas@HIDDEN>; Maintainer for emacs is bug-gnu-emacs@HIDDEN.

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Subject: Re: bug#2816: regexp-opt: does not optimize 'Abc' and 'abc'.
To: Stefan Monnier <monnier@HIDDEN>
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Stefan Monnier <monnier@HIDDEN> writes:

>> A)
>
>>     (regexp-opt
>>       '("Abc"
>>         "abc"))
>
>>     => "\\(?:[Aa]bc\\)"
>
>> B)
>
>>     (regexp-opt
>>       '("Abc"
>>         "def"
>>         "abc"))
>
>>     => "\\(?:Abc\\|abc\\|def\\)"
>
>> Shouldn't regexp-opt optimize B case as well?
>
> The `opt' of regexp-opt should be understood in the sense of
> optimization used in compilers, not in the formal mathematical sense of
> "optimal".  I.e. it does some effort to improve things, but without any
> guarantee about what is and what isn't optimized.
>
> So, yes, it would be good if it did do what you suggest, but it's not
> a bug if it doesn't.

Without a proposed patch, I think it's unlikely that we'll make much
progress here.  After 16 years, I'm closing this bug now.

If anyone wants to propose improvements to `regexp-opt`, please open a
new bug report.
Information forwarded to bug-gnu-emacs@HIDDEN:
bug#2816; Package emacs. Full text available.

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Subject: Re: bug#2816: regexp-opt: does not optimize 'Abc' and 'abc'
To: Stefan Monnier <monnier@HIDDEN>
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Stefan Monnier <monnier@HIDDEN> writes:

>> A)
>
>>     (regexp-opt
>>       '("Abc"
>>         "abc"))
>
>>     => "\\(?:[Aa]bc\\)"
>
>> B)
>
>>     (regexp-opt
>>       '("Abc"
>>         "def"
>>         "abc"))
>
>>     => "\\(?:Abc\\|abc\\|def\\)"
>
>> Shouldn't regexp-opt optimize B case as well?
>
> The `opt' of regexp-opt should be understood in the sense of
> optimization used in compilers, not in the formal mathematical sense of
> "optimal".  I.e. it does some effort to improve things, but without any
> guarantee about what is and what isn't optimized.
>
> So, yes, it would be good if it did do what you suggest, but it's not
> a bug if it doesn't.

Without a proposed patch, I think it's unlikely that we'll make much
progress here.  After 16 years, I'm closing this bug now.

If anyone wants to propose improvements to `regexp-opt`, please open a
new bug report.
Notification sent to Jari Aalto <jari.aalto@HIDDEN>:
bug acknowledged by developer. Full text available.
Reply sent to Stefan Kangas <stefankangas@HIDDEN>:
You have taken responsibility. Full text available.
Tags removed: patch Request was from Glenn Morris <rgm@HIDDEN> to control@HIDDEN. Full text available.
Severity set to `wishlist' from `normal' Request was from Jari Aalto <jari.aalto@HIDDEN> to control@HIDDEN. Full text available.

Message received at 2816@HIDDEN:


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From: Stefan Monnier <monnier@HIDDEN>
To: Jari Aalto <jari.aalto@HIDDEN>
Cc: 2816 <at> debbugs.gnu.org,
        Emacs bug BTS <submit <at> debbugs.gnu.org>
Subject: Re: bug#2816: regexp-opt: does not optimize 'Abc' and 'abc'
Message-ID: <jwvy6uo9rwy.fsf-monnier+emacsbugreports@HIDDEN>
References: <877i28nya0.fsf@HIDDEN>
Date: Sun, 29 Mar 2009 13:13:09 -0400
In-Reply-To: <877i28nya0.fsf@HIDDEN> (Jari Aalto's message of "Sun,
	29 Mar 2009 18:28:55 +0300")
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> A)

>     (regexp-opt
>       '("Abc"
>         "abc"))

>     => "\\(?:[Aa]bc\\)"

> B)

>     (regexp-opt
>       '("Abc"
>         "def"
>         "abc"))

>     => "\\(?:Abc\\|abc\\|def\\)"

> Shouldn't regexp-opt optimize B case as well?

The `opt' of regexp-opt should be understood in the sense of
optimization used in compilers, not in the formal mathematical sense of
"optimal".  I.e. it does some effort to improve things, but without any
guarantee about what is and what isn't optimized.

So, yes, it would be good if it did do what you suggest, but it's not
a bug if it doesn't.


        Stefan
Acknowledgement sent to Stefan Monnier <monnier@HIDDEN>:
Extra info received and forwarded to list. Copy sent to Emacs Bugs <bug-gnu-emacs@HIDDEN>. Full text available.
Information forwarded to bug-submit-list@HIDDEN, Emacs Bugs <bug-gnu-emacs@HIDDEN>:
bug#2816; Package emacs. Full text available.

Message received at submit@HIDDEN:


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From: Stefan Monnier <monnier@HIDDEN>
To: Jari Aalto <jari.aalto@HIDDEN>
Cc: 2816 <at> debbugs.gnu.org,
        Emacs bug BTS <submit <at> debbugs.gnu.org>
Subject: Re: bug#2816: regexp-opt: does not optimize 'Abc' and 'abc'
Message-ID: <jwvy6uo9rwy.fsf-monnier+emacsbugreports@HIDDEN>
References: <877i28nya0.fsf@HIDDEN>
Date: Sun, 29 Mar 2009 13:13:09 -0400
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	29 Mar 2009 18:28:55 +0300")
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> A)

>     (regexp-opt
>       '("Abc"
>         "abc"))

>     => "\\(?:[Aa]bc\\)"

> B)

>     (regexp-opt
>       '("Abc"
>         "def"
>         "abc"))

>     => "\\(?:Abc\\|abc\\|def\\)"

> Shouldn't regexp-opt optimize B case as well?

The `opt' of regexp-opt should be understood in the sense of
optimization used in compilers, not in the formal mathematical sense of
"optimal".  I.e. it does some effort to improve things, but without any
guarantee about what is and what isn't optimized.

So, yes, it would be good if it did do what you suggest, but it's not
a bug if it doesn't.


        Stefan
Acknowledgement sent to Stefan Monnier <monnier@HIDDEN>:
Extra info received and forwarded to list. Copy sent to Emacs Bugs <bug-gnu-emacs@HIDDEN>. Full text available.
Information forwarded to bug-submit-list@HIDDEN, Emacs Bugs <bug-gnu-emacs@HIDDEN>:
bug#2816; Package emacs. Full text available.
Tags added: patch Request was from Jari Aalto <jari.aalto@HIDDEN> to control@HIDDEN. Full text available.

Message received at submit@HIDDEN:


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From: Jari Aalto <jari.aalto@HIDDEN>
To: Emacs bug BTS <submit <at> debbugs.gnu.org>
Subject: regexp-opt: does not optimize 'Abc' and 'abc'
Date: Sun, 29 Mar 2009 18:28:55 +0300
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A)

    (regexp-opt
      '("Abc"
        "abc"))

    => "\\(?:[Aa]bc\\)"

B)

    (regexp-opt
      '("Abc"
        "def"
        "abc"))

    => "\\(?:Abc\\|abc\\|def\\)"

Shouldn't regexp-opt optimize B case as well?

Jari
Acknowledgement sent to Jari Aalto <jari.aalto@HIDDEN>:
New bug report received and forwarded. Copy sent to Emacs Bugs <bug-gnu-emacs@HIDDEN>. Full text available.
Report forwarded to bug-submit-list@HIDDEN, Emacs Bugs <bug-gnu-emacs@HIDDEN>:
bug#2816; Package emacs. Full text available.
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