[#45426] [ruby-trunk - Feature #6546][Open] Net::HTTP to check for HTTP_PROXY environment setting. — "dekz (Jacob Evans)" <dekzter@...>

14 messages 2012/06/04

[#45431] [ruby-trunk - Bug #6548][Open] Rake doesn't ignore arguments after -- — "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>

12 messages 2012/06/05

[#45474] [ANN] Request for "slide-show" of your feature proposal — Yusuke Endoh <mame@...>

(Japanese later; 日本語が後にあります)

18 messages 2012/06/07

[#45563] [ruby-trunk - Bug #6573][Open] Webrick test failures — "bkabrda (Bohuslav Kabrda)" <bkabrda@...>

19 messages 2012/06/11

[#45567] [ruby-trunk - Bug #6575][Open] Thread#kill sets rb_errinfo() to Fixnum 8 after rb_protect(function, data, &error_tag) — ibc (Iñaki Baz Castillo) <ibc@...>

9 messages 2012/06/11

[#45647] [ruby-trunk - Bug #6592][Open] test_call_double(DL::TestDL) fails on ARM HardFP — "vo.x (Vit Ondruch)" <v.ondruch@...>

15 messages 2012/06/14

[#45657] [ruby-trunk - Feature #6594][Open] Integrated Functor — "trans (Thomas Sawyer)" <transfire@...>

20 messages 2012/06/15

[#45664] [ruby-trunk - Bug #6596][Open] New method for Arrays : Array#index — "robin850 (Robin Dupret)" <robin.dupret@...>

20 messages 2012/06/15

[#45694] [ruby-trunk - Feature #6602][Open] Tail call optimization: enable by default? — "ko1 (Koichi Sasada)" <redmine@...>

12 messages 2012/06/18

[#45715] [ruby-trunk - Feature #6609][Open] Toplevel as self extended module — "trans (Thomas Sawyer)" <transfire@...>

17 messages 2012/06/19

[#45732] [ruby-trunk - Bug #6614][Open] GC doesn't collect objects bound to (collectable) proc — "rogerdpack (Roger Pack)" <rogerpack2005@...>

9 messages 2012/06/20

[#45733] [ruby-trunk - Feature #6615][Open] Release GVL in zlib when calling inflate() or deflate() — "drbrain (Eric Hodel)" <[email protected]>

12 messages 2012/06/21

[#45735] [ruby-trunk - Bug #6616][Open] MinGW: cannot build extensions or run tests due changes in exec_arg? — "luislavena (Luis Lavena)" <luislavena@...>

9 messages 2012/06/21

[#45798] [ruby-trunk - Bug #6634][Open] Deadlock with join and ConditionVariable — "meh. (meh. I don't care)" <meh@...>

20 messages 2012/06/23

[#45805] [ruby-trunk - Feature #6636][Open] Enumerable#size — "marcandre (Marc-Andre Lafortune)" <ruby-core@...>

15 messages 2012/06/23

[#45864] [ruby-trunk - Bug #6647][Open] Exceptions raised in threads should be logged — "headius (Charles Nutter)" <headius@...>

71 messages 2012/06/25

[#45902] [ruby-trunk - Bug #6653][Open] 1.9.2/1.9.3 exhibit SEGV with many threads+tcp connections — "erikh (Erik Hollensbe)" <erik@...>

11 messages 2012/06/26

[#45960] [ruby-trunk - Feature #6669][Open] A method like Hash#map but returns hash — "yhara (Yutaka HARA)" <redmine@...>

18 messages 2012/06/29

[#45963] [ruby-trunk - Feature #6670][Open] str.chars.last should be possible — "yhara (Yutaka HARA)" <redmine@...>

36 messages 2012/06/29

[#46021] [ruby-trunk - Feature #6679][Open] Default Ruby source file encoding to utf-8 — "claytrump (Clay Trump)" <clay.trump@...>

21 messages 2012/06/30

[ruby-core:45416] [ruby-trunk - Feature #6515] array.c: added method that verifies if an Array is part of another

From: "Eregon (Benoit Daloze)" <redmine@...>
Date: 2012-06-04 08:35:02 UTC
List: ruby-core #45416
Issue #6515 has been updated by Eregon (Benoit Daloze).


lellisga (Li Ellis Galardo) wrote:
> a = [1,2,3,4,5,6,7].to_set
>  => #<Set: {1, 2, 3, 4, 5, 6, 7}> 
> b = [1,2,3].to_set
>  => #<Set: {1, 2, 3}> 
> b.subset? a
>  => true 
> 
> If you answer is yes, then we are doing this wrong because subset? or part_of method should be in a parent class (maybe Enumerable class ) in order for it to work for subset, array, hash and any data structure that inherit from it Enumerable.

Taking you example of a the first set and b the maybe-subset:
Well, probably because #subset? is O(m) (m is the size of b), and doing it naively on Array/Enumerable is O(m*n) (n being the size of a). Using (b-a).empty? is actually O(n+m) because it creates a hash (think set in this case) underneath and iterates b. Note Array#- mentions the Set library, because it's likely what you want if you need this kind of operations. Of course you might need both Array and Set operations, in which case you may:
- transform them to set when needed: which is O(n+m + m) so O(n+m).
- use (a-b).empty? which I believe is clear and concise (although a comment might help for other readers) but creates the diff Array for nothing. You might want something like:

  as = a.to_set
  b.all? { |e| as.include?(e) }

Which does not allocate an intermediary Array, and is O(n+m) as well.

Often, when you want this kind of behavior, you don't need Array-specific operations, which is why using a Set directly is better (and usually more efficient).
----------------------------------------
Feature #6515: array.c: added method that verifies if an Array is part of another
https://bugs.ruby-lang.org/issues/6515#change-27005

Author: lellisga (Li Ellis Galardo)
Status: Feedback
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: 
Target version: 2.0.0


This method is like the include? method but instead of receiving a value and check if the array has it, it receives an array an check if it's part of another one.

https://github.com/ruby/ruby/pull/127


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