Issue #17030 has been updated by marcandre (Marc-Andre Lafortune).


Dan0042 (Daniel DeLorme) wrote in #note-17:
> 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.

Agreed

> > 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)

You are right, my bad.



----------------------------------------
Bug #17030: Enumerable#grep{_v} should be optimized for Regexp
https://bugs.ruby-lang.org/issues/17030#change-87213

* 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) }
```

is about three times faster and six times more memory efficient than

```ruby
array.grep(REGEXP)
```

This is because `grep` calls `Regexp#===`, which creates useless `MatchData`.



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