From: daniel@dan42.com
To: ruby-core@ruby-lang.org
Subject: [ruby-core:99716] [Ruby master Bug#17030] Enumerable#grep{_v} should be optimized for Regexp
Date: Wed, 26 Aug 2020 20:43:44 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-87206.20200826204337.182@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-17030.20200713202650.182@ruby-lang.org
Issue #17030 has been updated by Dan0042 (Daniel DeLorme).
What about this?
```ruby
2.times do
p $~ # depends on match *below*
rx =~ str
end
```
Now imagine if `2.times` is replaced by `foo`; a priori we can't know if or how many times the block will be executed. So what I was trying to say is that flow control can lead to all kinds of code paths where it's extremely difficult to know which matching operations a pseudo-global may depend on. Maybe not impossible, but personally I wouldn't want to code that kind of analysis when a simple approach is enough for >90% of cases, and guaranteed to be bug-free.
> There will be other false positives: `str.gsub(regexp, &block)`. That's not a real issue, simply assume that `block` will want access to `Regexp.last_match`.
Actually... `block` does not have access to `Regexp.last_match` (unless you created the block in the same scope as the gsub operation, but that would be unusual)
----------------------------------------
Bug #17030: Enumerable#grep{_v} should be optimized for Regexp
https://bugs.ruby-lang.org/issues/17030#change-87206
* Author: marcandre (Marc-Andre Lafortune)
* Status: Open
* Priority: Normal
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
Currently:
```ruby
array.select { |e| e.match?(REGEXP) }
# about 3x faster and 6x more memory efficient than
array.grep(REGEXP)
```
This is because `grep` calls `Regexp#===` which creates useless `MatchData`
--
https://bugs.ruby-lang.org/
next prev parent reply other threads:[~2020-08-26 20:43 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-13 20:26 [ruby-core:99156] [Ruby master Bug#17030] Enumerable#grep{_v} should be optimized for Regexp marcandre-ruby-core
2020-07-13 20:27 ` [ruby-core:99157] " marcandre-ruby-core
2020-07-14 1:24 ` [ruby-core:99161] " shyouhei
2020-07-14 3:37 ` [ruby-core:99163] " marcandre-ruby-core
2020-07-14 10:25 ` [ruby-core:99164] " nobu
2020-07-14 13:28 ` [ruby-core:99165] " eregontp
2020-07-14 13:46 ` [ruby-core:99166] " marcandre-ruby-core
2020-07-21 11:27 ` [ruby-core:99248] " scivola20
2020-08-25 17:23 ` [ruby-core:99687] " fatkodima123
2020-08-25 22:09 ` [ruby-core:99690] " fatkodima123
2020-08-25 23:37 ` [ruby-core:99692] " sawadatsuyoshi
2020-08-26 8:31 ` [ruby-core:99702] " fatkodima123
2020-08-26 15:01 ` [ruby-core:99705] " marcandre-ruby-core
2020-08-26 17:01 ` [ruby-core:99706] " fatkodima123
2020-08-26 17:30 ` [ruby-core:99708] " marcandre-ruby-core
2020-08-26 19:17 ` [ruby-core:99713] " daniel
2020-08-26 19:31 ` [ruby-core:99714] " marcandre-ruby-core
2020-08-26 20:43 ` daniel [this message]
2020-08-27 2:10 ` [ruby-core:99722] " marcandre-ruby-core
2020-08-27 8:03 ` [ruby-core:99729] " fatkodima123
2020-08-27 16:58 ` [ruby-core:99737] " daniel
2020-08-27 17:16 ` [ruby-core:99738] " merch-redmine
2020-08-28 15:01 ` [ruby-core:99751] " eregontp
2020-08-28 15:30 ` [ruby-core:99752] " eregontp
2020-09-25 6:53 ` [ruby-core:100127] " matz
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