[#55222] [ruby-trunk - Feature #8468][Feedback] Remove $SAFE — "shugo (Shugo Maeda)" <redmine@...>

20 messages 2013/06/01

[#55260] [ruby-trunk - Feature #8478][Open] The hash returned by Enumerable#group_by should have an empty array for its default value — "phiggins (Pete Higgins)" <pete@...>

8 messages 2013/06/02

[#55276] Re: [ruby-changes:28951] zzak:r41003 (trunk): * process.c: Improve Process::exec documentation — Tanaka Akira <akr@...>

2013/5/31 zzak <[email protected]>:

9 messages 2013/06/03

[#55306] [ruby-trunk - Feature #8490][Open] Bring ActiveSupport Enumerable#index_by to core — "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>

12 messages 2013/06/04

[#55330] [ruby-trunk - Feature #8499][Assigned] Importing Hash#slice, Hash#slice!, Hash#except, and Hash#except! from ActiveSupport — "mrkn (Kenta Murata)" <muraken@...>

30 messages 2013/06/06

[#55391] [ruby-trunk - Bug #8507][Open] Keyword splat does not convert arg to Hash — "stephencelis (Stephen Celis)" <stephen.celis@...>

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[#55393] [ruby-trunk - Bug #8508][Open] Invalid byte sequence in UTF-8 (ArgumentError) in win32/registry.rb — "thasmo (Thomas Deinhamer)" <thasmo@...>

11 messages 2013/06/09

[#55528] [ruby-trunk - Bug #8538][Open] c method not pushed into the callstack when called, but popped when returned — deivid (David Rodríguez) <deivid.rodriguez@...>

9 messages 2013/06/17

[#55557] [ruby-trunk - misc #8543][Open] rb_iseq_load — "alvoskov (Alexey Voskov)" <alvoskov@...>

47 messages 2013/06/19

[#55558] [ruby-trunk - Feature #8544][Open] OpenURI should open 'file://' URIs — "silasdavis (Silas Davis)" <ruby-lang@...>

12 messages 2013/06/19

[#55580] [CommonRuby - Feature #8556][Open] MutexedDelegator as a trivial way to make an object thread-safe — "headius (Charles Nutter)" <headius@...>

19 messages 2013/06/21

[#55596] [ruby-trunk - Feature #8563][Open] Instance variable arguments — "sawa (Tsuyoshi Sawada)" <sawadatsuyoshi@...>

18 messages 2013/06/22

[#55638] [CommonRuby - Feature #8568][Open] Introduce RbConfig value for native word size, to avoid Fixnum#size use — "headius (Charles Nutter)" <headius@...>

18 messages 2013/06/24

[#55678] [ruby-trunk - Feature #8572][Open] Fiber should be a Enumerable — "mattn (Yasuhiro Matsumoto)" <mattn.jp@...>

13 messages 2013/06/28

[#55699] [ruby-trunk - Feature #8579][Open] Frozen string syntax — "charliesome (Charlie Somerville)" <charliesome@...>

20 messages 2013/06/29

[#55708] [ruby-trunk - Bug #8584][Assigned] Remove curses — "shugo (Shugo Maeda)" <redmine@...>

17 messages 2013/06/30

[ruby-core:55269] [ruby-trunk - Feature #8478] The hash returned by Enumerable#group_by should have an empty array for its default value

From: duerst (Martin Dürst) <duerst@...>
Date: 2013-06-03 06:57:05 UTC
List: ruby-core #55269
Issue #8478 has been updated by duerst (Martin D端rst).


I don't think I agree with the proposer. The example looks good, but what about something like:

a = [1, 2, 3, "a", "b"]
g = a.group_by {|o| o.class }

puts "Fixnums: #{g[Fixnum].size}"
puts "Strings: #{g[String].size}"
puts "Zeroes: #{g[0].size}"

In other words, it might be desirable to return an empty array for a group key that is part of the collection that we group over (classes in the example), but it'd be better to cause an error for group keys that are outside of the collection (i.e., not classes in the example).

That would mean that the default proc should (for this example) be something like
    {|hash, key| hash[key] = [] if key.class==Class }
Of course, that cannot be part of Ruby, unless maybe as a third argument of some form to group_by.


----------------------------------------
Feature #8478: The hash returned by Enumerable#group_by should have an empty array for its default value
https://bugs.ruby-lang.org/issues/8478#change-39663

Author: phiggins (Pete Higgins)
Status: Open
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: 
Target version: 


Without this patch, nil checks might need to be done on the return value of Enumerable#group_by:

$ cat test_group_by.rb 
a = [1, 2, 3, "a", "b"]
g = a.group_by {|o| o.class }

puts "Fixnums: #{g[Fixnum].size}"
puts "Strings: #{g[String].size}"
puts "Arrays: #{g[Array].size}"

$ ruby test_group_by.rb 
Fixnums: 3
Strings: 2
test_group_by.rb:6:in `<main>': undefined method `size' for nil:NilClass (NoMethodError)

This patch adds a default value of an empty array to the hash returned by Enumerable#group_by, so the script above will work:

$ ./ruby -I.:lib test_group_by.rb 
Fixnums: 3
Strings: 2
Arrays: 0



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