[ruby-core:113368] [Ruby master Feature#8707] Hash#reverse_each
From:
"bughit (bug hit) via ruby-core" <ruby-core@...>
Date:
2023-04-27 20:28:44 UTC
List:
ruby-core #113368
Issue #8707 has been updated by bughit (bug hit).
> Do we really need it? What is use-cases?
When you have an ordered collection it seems self evident that you may need to iterate in reverse. This would for example back a performant `last(n = 1)` method (#12165)
Would you demand to know why one may want the last n elements of an array? These are both ordered collections, if `last(n = 1)` makes sense for one, it makes sense for the other.
Why is this closed with a status of "Feedback"?
----------------------------------------
Feature #8707: Hash#reverse_each
https://bugs.ruby-lang.org/issues/8707#change-102934
* Author: Glass_saga (Masaki Matsushita)
* Status: Feedback
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
----------------------------------------
Currently, {}.reverse_each calls Enumerable#reverse_each.
It will make array and its size can be large.
I made Hash#reverse_each to avoid array creation and performance improvement.
benchmark:
require "benchmark"
Size = 10000
HASH = Hash[*Array.new(Size) {|i| [i, true] }.flatten]
Benchmark.bmbm do |x|
x.report("Hash#reverse_each") do
300.times do
HASH.reverse_each {|a, b|}
end
end
end
result:
trunk(r42256):
Rehearsal -----------------------------------------------------
Hash#reverse_each 1.210000 0.000000 1.210000 ( 1.207964)
-------------------------------------------- total: 1.210000sec
user system total real
Hash#reverse_each 0.950000 0.000000 0.950000 ( 0.951069)
proposal:
Rehearsal -----------------------------------------------------
Hash#reverse_each 0.600000 0.000000 0.600000 ( 0.600242)
-------------------------------------------- total: 0.600000sec
user system total real
Hash#reverse_each 0.450000 0.000000 0.450000 ( 0.459006)
---Files--------------------------------
patch.diff (7.55 KB)
--
https://bugs.ruby-lang.org/
______________________________________________
ruby-core mailing list -- [email protected]
To unsubscribe send an email to [email protected]
ruby-core info -- https://ml.ruby-lang.org/mailman3/postorius/lists/ruby-core.ml.ruby-lang.org/