[#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:46013] [ruby-trunk - Feature #4151] Enumerable#categorize

From: "Eregon (Benoit Daloze)" <redmine@...>
Date: 2012-06-30 19:57:26 UTC
List: ruby-core #46013
Issue #4151 has been updated by Eregon (Benoit Daloze).

File feature4151.pdf added

marcandre (Marc-Andre Lafortune) wrote:
> Attaching one-minute slide-show

Attaching mine.
I hope both can be shown if it makes sense, after all there are many features about this.
----------------------------------------
Feature #4151: Enumerable#categorize
https://bugs.ruby-lang.org/issues/4151#change-27617

Author: akr (Akira Tanaka)
Status: Assigned
Priority: Low
Assignee: akr (Akira Tanaka)
Category: 
Target version: 2.0.0


=begin
 Hi.
 
 How about a method for converting enumerable to hash?
 
   enum.categorize([opts]) {|elt| [key1, ..., val] } -> hash
 
 categorizes the elements in _enum_ and returns a hash.
 
 The block is called for each elements in _enum_.
 The block should return an array which contains
 one or more keys and one value.
 
   p (0..10).categorize {|e| [e % 3, e % 5] }
   #=> {0=>[0, 3, 1, 4], 1=>[1, 4, 2, 0], 2=>[2, 0, 3]}
 
 The keys and value are used to construct the result hash.
 If two or more keys are provided
 (i.e. the length of the array is longer than 2),
 the result hash will be nested.
 
   p (0..10).categorize {|e| [e&4, e&2, e&1, e] }
   #=> {0=>{0=>{0=>[0, 8],
   #            1=>[1, 9]},
   #        2=>{0=>[2, 10],
   #            1=>[3]}},
   #    4=>{0=>{0=>[4],
   #            1=>[5]},
   #        2=>{0=>[6],
   #            1=>[7]}}}
 
 The value of innermost hash is an array which contains values for
 corresponding keys.
 This behavior can be customized by :seed, :op and :update option.
 
 This method can take an option hash.
 Available options are follows:
 
 - :seed specifies seed value.
 - :op specifies a procedure from seed and value to next seed.
 - :update specifies a procedure from seed and block value to next seed.
 
 :seed, :op and :update customizes how to generate
 the innermost hash value.
 :seed and :op behavies like Enumerable#inject.
 
 If _seed_ and _op_ is specified, the result value is generated as follows.
   op.call(..., op.call(op.call(seed, v0), v1), ...)
 
 :update works as :op except the second argument is the block value itself
 instead of the last value of the block value.
 
 If :seed option is not given, the first value is used as the seed.
 
   # The arguments for :op option procedure are the seed and the value.
   # (i.e. the last element of the array returned from the block.)
   r = [0].categorize(:seed => :s,
                      :op => lambda {|x,y|
                        p [x,y]               #=> [:s, :v]
                        1
                      }) {|e|
     p e #=> 0
     [:k, :v]
   }
   p r #=> {:k=>1}
 
   # The arguments for :update option procedure are the seed and the array
   # returned from the block.
   r = [0].categorize(:seed => :s,
                      :update => lambda {|x,y|
                        p [x,y]               #=> [:s, [:k, :v]]
                        1
                      }) {|e|
     p e #=> 0
     [:k, :v]
   }
   p r #=> {:k=>1}
 
 The default behavior, array construction, can be implemented as follows.
   :seed => nil
   :op => lambda {|s, v| !s ? [v] : (s << v) }
 
 Note that matz doesn't find satisfact in the method name, "categorize".
 [ruby-dev:42681]
 
 Also note that matz wants another method than this method,
 which the hash value is the last value, not an array of all values.
 This can be implemented by enum.categorize(:op=>lambda {|x,y| y}) { ... }.
 But good method name is not found yet.
 [ruby-dev:42643]
 -- 
 Tanaka Akira
 
 Attachment: enum-categorize.patch
=end



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