[ruby-core:115011] [Ruby master Feature#18515] Add Range#reverse_each implementation
From:
"matz (Yukihiro Matsumoto) via ruby-core" <ruby-core@...>
Date:
2023-10-12 07:59:22 UTC
List:
ruby-core #115011
Issue #18515 has been updated by matz (Yukihiro Matsumoto).
I accept this as a performance improvement.
Matz.
----------------------------------------
Feature #18515: Add Range#reverse_each implementation
https://bugs.ruby-lang.org/issues/18515#change-104881
* Author: kyanagi (Kouhei Yanagita)
* Status: Open
* Priority: Normal
----------------------------------------
PR is ~~https://github.com/ruby/ruby/pull/5489~~ https://github.com/ruby/ruby/pull/8525
Current `Range#reverse_each` uses `Enumerable#reverse_each` which is implemented with `#to_a`.
So we are virtually not able to use `reverse_each` for a very large or beginless range, even if few elements are iterated on actually.
```
(1..2**100).reverse_each { |x| p x; break if x.odd? }
(..5).reverse_each { |x| p x; break if x == 0 }
(1..2**32).reverse_each.lazy.select { |x| Prime.prime?(x) }.take(3).to_a
```
This patch, implements `Range#reverse_each` for Integer elements, enables these examples.
I think `#reverse_each` for an endless range should raise an exception.
This is a different issue, so I'll create another ticket later.
-> posted: https://bugs.ruby-lang.org/issues/18551
--
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