From: Johannes Sixt <j6t@kdbg.org>
To: "Junio C Hamano" <gitster@pobox.com>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: git@vger.kernel.org,
"Carlo Marcelo Arenas Belón" <carenas@gmail.com>,
"Johannes Schindelin" <Johannes.Schindelin@gmx.de>,
"Todd Zullinger" <tmz@pobox.com>
Subject: Re: [PATCH v3 2/4] grep/pcre2: simplify boolean spaghetti
Date: Sun, 24 Jan 2021 11:45:39 +0100 [thread overview]
Message-ID: <ac4f3b95-49f7-7a90-b7f7-9efbb57a7392@kdbg.org> (raw)
In-Reply-To: <xmqqim7m292j.fsf@gitster.c.googlers.com>
Am 24.01.21 um 06:33 schrieb Junio C Hamano:
> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>
>> NOT(A && B) is Equivalent to (NOT(A) OR NOT(B))
>
> At this level, however, the left one looks much simpler than the
> right one ;-)
>
>
>> if (!opt->ignore_locale && is_utf8_locale() && has_non_ascii(p->pattern) &&
>> - !(!opt->ignore_case && (p->fixed || p->is_fixed)))
>> + (opt->ignore_case || !(p->fixed || p->is_fixed)))
>> options |= PCRE2_UTF;
>
> In the context of this expression, well, I guess the rewritten one
> is probably simpler but can we explain the whole condition in fewer
> than three lines? With or without the rewrite, it still looks too
> complicated to me.
Make the condition
if (!opt->ignore_locale &&
is_utf8_locale() &&
has_non_ascii(p->pattern) &&
(opt->ignore_case ||
(!p->fixed &&
!p->is_fixed)))
{
options |= PCRE2_UTF;
}
With the knowledge of the equivalence
(A => B) <=> (NOT(A) OR B)
(A => B means "if A then B"), the condition makes a lot of sense when
read aloud:
if
NOT ignore locale
AND
is UTF8
AND
has non-ASCII
AND
if
NOT ignore case
then if also
NOT fixed
AND
NOT is fixed
then
...
The codition amounts to extending a series of conjunctions with more
conjuctions IF a condition is satisfied. That's quite sensible.
You have to swap the polarity of the first condition of || in your head,
though, to achieve that meaning. That works with every OR condition, BTW.
-- Hannes
next prev parent reply other threads:[~2021-01-24 10:50 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-21 19:40 [PATCH] grep: use custom JIT stack with pcre2 Carlo Marcelo Arenas Belón
2019-07-24 15:14 ` [PATCH 0/3] grep: PCRE JIT fixes Ævar Arnfjörð Bjarmason
2019-07-24 16:18 ` Junio C Hamano
2019-07-24 20:03 ` Ævar Arnfjörð Bjarmason
2019-07-26 15:08 ` [PATCH v2 0/8] grep: PCRE JIT fixes + ab/no-kwset fix Ævar Arnfjörð Bjarmason
2019-07-26 20:27 ` Junio C Hamano
2019-07-29 9:20 ` Ævar Arnfjörð Bjarmason
2019-07-29 16:12 ` Junio C Hamano
2019-07-26 15:08 ` [PATCH v2 1/8] grep: remove overly paranoid BUG(...) code Ævar Arnfjörð Bjarmason
2019-07-26 15:08 ` [PATCH v2 2/8] grep: stop "using" a custom JIT stack with PCRE v2 Ævar Arnfjörð Bjarmason
2019-07-29 0:33 ` Carlo Arenas
2019-07-26 15:08 ` [PATCH v2 3/8] grep: stop using a custom JIT stack with PCRE v1 Ævar Arnfjörð Bjarmason
2019-07-29 1:26 ` Carlo Arenas
2019-07-26 15:08 ` [PATCH v2 4/8] grep: consistently use "p->fixed" in compile_regexp() Ævar Arnfjörð Bjarmason
2019-07-29 1:48 ` Carlo Arenas
2019-07-29 9:05 ` Ævar Arnfjörð Bjarmason
2019-07-29 9:13 ` Ævar Arnfjörð Bjarmason
2019-07-29 16:23 ` Junio C Hamano
2019-07-26 15:08 ` [PATCH v2 5/8] grep: create a "is_fixed" member in "grep_pat" Ævar Arnfjörð Bjarmason
2019-07-26 15:08 ` [PATCH v2 6/8] grep: stess test PCRE v2 on invalid UTF-8 data Ævar Arnfjörð Bjarmason
2019-07-26 20:34 ` Junio C Hamano
2019-07-26 21:55 ` Ævar Arnfjörð Bjarmason
2019-07-29 3:06 ` Carlo Arenas
2019-11-26 21:50 ` [PATCH] t7812: add missing redirects Andreas Schwab
2019-11-26 22:27 ` Johannes Schindelin
2019-11-26 23:11 ` Andreas Schwab
2019-11-27 11:58 ` Jeff King
2019-11-30 0:46 ` [PATCH] t7812: expect failure for grep -i with invalid UTF-8 data Todd Zullinger
2019-11-30 8:00 ` Andreas Schwab
2019-12-01 16:33 ` Junio C Hamano
2019-12-01 17:09 ` Andreas Schwab
2019-12-01 18:32 ` Todd Zullinger
2019-12-02 6:13 ` Junio C Hamano
2019-07-26 15:08 ` [PATCH v2 7/8] grep: do not enter PCRE2_UTF mode on fixed matching Ævar Arnfjörð Bjarmason
2019-07-26 20:36 ` Junio C Hamano
2019-07-26 15:08 ` [PATCH v2 8/8] grep: optimistically use PCRE2_MATCH_INVALID_UTF Ævar Arnfjörð Bjarmason
2019-07-26 21:07 ` Junio C Hamano
2019-07-26 21:53 ` Ævar Arnfjörð Bjarmason
2019-07-26 21:57 ` Ævar Arnfjörð Bjarmason
2021-01-24 2:12 ` [PATCH v3 0/4] grep: better support invalid UTF-8 haystacks Ævar Arnfjörð Bjarmason
2021-01-24 11:48 ` [PATCH v4 0/2] " Ævar Arnfjörð Bjarmason
2021-01-24 17:28 ` [PATCH v5 " Ævar Arnfjörð Bjarmason
2021-01-24 17:28 ` [PATCH v5 1/2] grep/pcre2 tests: don't rely on invalid UTF-8 data test Ævar Arnfjörð Bjarmason
2021-01-24 17:28 ` [PATCH v5 2/2] grep/pcre2: better support invalid UTF-8 haystacks Ævar Arnfjörð Bjarmason
2021-01-24 11:48 ` [PATCH v4 1/2] grep/pcre2 tests: don't rely on invalid UTF-8 data test Ævar Arnfjörð Bjarmason
2021-01-24 11:48 ` [PATCH v4 2/2] grep/pcre2: better support invalid UTF-8 haystacks Ævar Arnfjörð Bjarmason
2021-01-24 13:53 ` Ramsay Jones
2021-01-24 14:24 ` Ramsay Jones
2021-01-24 14:49 ` Ævar Arnfjörð Bjarmason
2021-01-24 16:10 ` Ramsay Jones
2021-01-24 17:29 ` Ævar Arnfjörð Bjarmason
2021-01-24 2:12 ` [PATCH v3 1/4] grep/pcre2 tests: don't rely on invalid UTF-8 data test Ævar Arnfjörð Bjarmason
2021-01-24 2:12 ` [PATCH v3 2/4] grep/pcre2: simplify boolean spaghetti Ævar Arnfjörð Bjarmason
2021-01-24 5:33 ` Junio C Hamano
2021-01-24 10:45 ` Johannes Sixt [this message]
2021-01-24 2:12 ` [PATCH v3 3/4] grep/pcre2: further " Ævar Arnfjörð Bjarmason
2021-01-24 2:12 ` [PATCH v3 4/4] grep/pcre2: better support invalid UTF-8 haystacks Ævar Arnfjörð Bjarmason
2019-07-24 15:14 ` [PATCH 1/3] grep: remove overly paranoid BUG(...) code Ævar Arnfjörð Bjarmason
2019-07-24 15:14 ` [PATCH 2/3] grep: stop "using" a custom JIT stack with PCRE v2 Ævar Arnfjörð Bjarmason
2019-07-24 16:24 ` Junio C Hamano
2019-07-24 20:06 ` Ævar Arnfjörð Bjarmason
2019-07-25 5:11 ` Carlo Arenas
2019-07-24 15:14 ` [PATCH 3/3] grep: stop using a custom JIT stack with PCRE v1 Ævar Arnfjörð Bjarmason
2019-07-26 13:15 ` Carlo Arenas
2019-07-26 13:50 ` Ævar Arnfjörð Bjarmason
2019-07-26 14:12 ` Carlo Arenas
2019-07-26 14:43 ` Ævar Arnfjörð Bjarmason
2019-07-26 20:26 ` [RFC PATCH 0/2] PCRE1 cleanup Carlo Marcelo Arenas Belón
2019-07-26 20:26 ` [RFC PATCH 1/2] grep: make sure NO_LIBPCRE1_JIT disable JIT in PCRE1 Carlo Marcelo Arenas Belón
2019-07-26 20:26 ` [RFC PATCH 2/2] grep: refactor and simplify PCRE1 support Carlo Marcelo Arenas Belón
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ac4f3b95-49f7-7a90-b7f7-9efbb57a7392@kdbg.org \
--to=j6t@kdbg.org \
--cc=Johannes.Schindelin@gmx.de \
--cc=avarab@gmail.com \
--cc=carenas@gmail.com \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=tmz@pobox.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).