[#46105] [ruby-trunk - Feature #6687][Open] Enumerable#with — "merborne (kyo endo)" <redmine@...>

14 messages 2012/07/02

[#46133] [ruby-trunk - Feature #6688][Open] Object#replace — "prijutme4ty (Ilya Vorontsov)" <prijutme4ty@...>

24 messages 2012/07/03

[#46160] [ruby-trunk - Feature #6693][Open] Don't warn for unused variables starting with _ — "marcandre (Marc-Andre Lafortune)" <ruby-core@...>

15 messages 2012/07/04

[#46200] [ruby-trunk - Bug #6702][Open] Date should be either required or not — "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>

14 messages 2012/07/05

[#46296] [ruby-trunk - Feature #6717][Open] Method like #instance_eval that returns self (like #tap) — "alexeymuranov (Alexey Muranov)" <redmine@...>

10 messages 2012/07/10

[#46320] [ruby-trunk - Feature #6721][Open] Object#yield_self — "alexeymuranov (Alexey Muranov)" <redmine@...>

25 messages 2012/07/11

[#46339] [ruby-trunk - Bug #6724][Open] waaaaaaant! ( — "zenspider (Ryan Davis)" <redmine@...>

11 messages 2012/07/11

[#46377] [ruby-trunk - Feature #6727][Open] Add Array#rest (with implementation) — "duckinator (Nick Markwell)" <nick@...>

25 messages 2012/07/13

[#46492] [ruby-trunk - Feature #6737][Open] Add Hash#read and alias as #[]. — "trans (Thomas Sawyer)" <transfire@...>

12 messages 2012/07/15

[#46500] [ruby-trunk - Feature #6739][Open] One-line rescue statement should support specifying an exception class — Quintus (Marvin Gülker) <sutniuq@...>

22 messages 2012/07/15

[#46562] [ruby-trunk - Feature #6758][Open] Object#sequence — "merborne (kyo endo)" <redmine@...>

19 messages 2012/07/20

[#46574] [ruby-trunk - Feature #6762][Open] Control interrupt timing — "ko1 (Koichi Sasada)" <redmine@...>

39 messages 2012/07/20

[#46641] [ruby-trunk - Bug #6780][Open] cannot compile zlib module, when cross-compiling. — "jinleileiking (lei king)" <jinleileiking@...>

14 messages 2012/07/23

[#46659] [ruby-trunk - Bug #6783][Open] Infinite loop in inspect, not overriding inspect, to_s, and no known circular references. Stepping into inspect in debugger locks it up with 100% CPU. — "garysweaver (Gary Weaver)" <garysweaver@...>

8 messages 2012/07/23

[#46792] [ruby-trunk - Bug #6799][Open] Digest::*.hexdigest returns an ASCII-8BIT String — "Eregon (Benoit Daloze)" <redmine@...>

11 messages 2012/07/26

[#46799] [ruby-trunk - Feature #6801][Open] String#~ for a here document — "merborne (kyo endo)" <redmine@...>

12 messages 2012/07/27

[#46829] [ruby-trunk - Feature #6806][Open] Support functional programming: forbid instance/class variables for ModuleName::method_name, allow for ModuleName.method_name — "alexeymuranov (Alexey Muranov)" <redmine@...>

7 messages 2012/07/28

[#46832] [ruby-trunk - Bug #6807][Open] Can't compile ruby without ruby — "devcurmudgeon (Paul Sherwood)" <storitel@...>

13 messages 2012/07/28

[#46834] [ruby-trunk - Feature #6808][Open] Implicit index for enumerations — "trans (Thomas Sawyer)" <transfire@...>

15 messages 2012/07/28

[#46838] [ruby-trunk - Bug #6810][Open] `module A::B; end` is not equivalent to `module A; module B; end; end` with respect to constant lookup (scope) — "alexeymuranov (Alexey Muranov)" <redmine@...>

17 messages 2012/07/28

[#46896] (Half-baked DRAFT) new `require' framework — SASADA Koichi <ko1@...>

Hi,

22 messages 2012/07/31

[ruby-core:46562] [ruby-trunk - Feature #6758][Open] Object#sequence

From: "merborne (kyo endo)" <redmine@...>
Date: 2012-07-20 04:38:10 UTC
List: ruby-core #46562
Issue #6758 has been reported by merborne (kyo endo).

----------------------------------------
Feature #6758: Object#sequence
https://bugs.ruby-lang.org/issues/6758

Author: merborne (kyo endo)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


=begin

== Object#sequence

Let me propose a new method ((*Object#sequence*)).

次のような実装の((*Object#sequence*))を提案します。

    class Object
      def sequence(init=true, &blk)
        x = self
        Enumerator.new do |y|
          y << x if init
          loop { y << (x = yield x) }
        end
      end
    end

((*sequence*)) generate a sequence by applying a block recursively to the receiver object. The result is wrapped with a Enumerator object, thus it is set under lazy evaluation.

((*sequence*))は、そのレシーバオブジェクトを初期値として、渡されたブロック(漸化式)を繰り返し適用してシーケンスを生成します。適用の結果はEnumeratorオブジェクトでラップされているので、遅延評価されます。

== Usage;

使い方を示します。

    1.sequence { |x| x + 2 }.take(10) # => [1, 3, 5, 7, 9, 11, 13, 15, 17, 19]
    
    3.sequence { |x| x * 2 }.take(10) # => [3, 6, 12, 24, 48, 96, 192, 384, 768, 1536]
    
    [0, 1].sequence { |a, b| [b, a + b] }.take(10).map(&:first) # => [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
    
    [0, 1, 1].sequence { |a, b, c| [b, c, a + b + c] }.take(10).map(&:first) # => [0, 1, 1, 2, 4, 7, 13, 24, 44, 81]
    
    # square root 5
    a = 5
    eps = 0.0001
    1.0.sequence { |x| (x + a/x) / 2.0 }
       .each_cons(2)
       .detect { |a, b| (a - b).abs < eps }[1] # => 2.236067977499978
    
    # Excel label
    'A'.sequence { |x| x.succ }.take(30) # => ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "AA", "AB", "AC", "AD"]
    
    # random boolean(avoid true-true sequence)
    true.sequence { |prev| prev ? false : [true, false].sample }.take(20) # => [true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, false, false, true, false]
    
== Some background

== 提案の経緯

Let me explain some background of this request.

本件に関しては、ここに至る若干の経緯がありますので、併せて説明します。

1. I introduced this method as ((*Object#repeat*)) on my Japanese blog.

1. 私のブログにおいて、本メソッドを((*Object#repeat*))として紹介する記事を公開。

((<URL:http://melborne.github.com/2012/07/12/object-repeat-take-care-of-sequence/>))

2. Matz tweeted to the article.

    > "um.. the feature is attractive, but the name is.." 

2. 記事に対してMatzがつぶやく。

    > 「うーん、昨日としては魅力的だけど、名前がなあ。」

((<URL:https://twitter.com/yukihiro_matz/status/223790181113806848>))


3. I updated the article to propose ((*Object#repeat_apply*)) or ((*Object#repeat_call*)).

3. Object#repeat_apply, Object#repeat_callを提案するべく記事を更新。

4. Matz tweeted to the article.

    > @merborne more clear. but combining two verbs is wrong. I understand naming is difficult.

4. 記事に対してMatzがつぶやく。

    > @merborne なるほど「repeat_apply」か「repeat_call」ですか。repeat単体よりは誤解を受けにくいとは思いますが、repeatって動詞とapply/callって動詞の組み合わせは感心しませんね。名前って難しい。 

((<URL:https://twitter.com/yukihiro_matz/status/224105896110866432>))

5. Matz tweeted to the article.

    > @merborne I suggest some clue lies around a word "series"..

5. 記事に対してMatzがつぶやく。

    > @merborne 「級数/series」あたりに名前のヒントがありそうな。

((<URL:https://twitter.com/yukihiro_matz/status/224106160591081472>))

6. I tweeted to Matz.

6. 私もつぶやく

    > @yukihiro_matz you are right.. `repeated_apply` `repeated_call`?.. 


    > @yukihiro_matz たしかに.. repeated_apply repeated_callかな.. 

((<URL:https://twitter.com/merborne/status/224108387653259264>))

    > @yukihiro_matz clue! `series_by` ? 


    > @yukihiro_matz ヒント! series_by ? 

((<URL:https://twitter.com/merborne/status/224108809948377088>))

    > @yukihiro_matz `repeated` is adjective..^^; but I don't like `repeatedly_apply`. I thought once `series_by` is good, but it would be better a method is named based on its behavior, not on its function, I think. How about `repeat_by`?


    > @yukihiro_matz repeatedは形容詞でしたね^^; するとrepeatedly_applyですが、今ひとつです。series_byもいいと思ったんですが、できれば機能ではなく動作を言いたい思いがあります。そこでrepeat_byというのはどうでしょうか。

((<URL:https://twitter.com/merborne/status/224324670764220416>))


the conversation closed..

会話終了..

7. Ideas from other Rubyists

Some Japanese Rubyists tweeted or commented me on the name. Candidates are..

7. 他のRubyistの意見

名前に関し何人かのRubyistからアイディアをもらっています。リストアップします。

    iterate
    recur
    recurrence
    recur_with
    unfold
    sequence
    seq



Haskell and Scala have the same functionality with a name of ((*iterate*)).


なお、HaskellとScalaには同種の機能が、((*iterate*))という名前で実装されているそうです。


Also, @makotokuwata-san tweeted that ((*Kernel#seq*))(function style) or ((*Enumerator.seq()*))(a Class method) is better.


また、@makotokuwata氏よりKernel#seqのような関数形式か、Enumerator.seq()のようなクラスメソッドのほうがいいとの意見も頂いています。

    > @yukihiro_matz @merborne 初期値と漸化式から順列を作る機能なので、"sequence"か"seq"に1票。あとKernel#seq(initial,&blk)のほうが好きです。RT 「級数/series」あたりに名前のヒントがありそうな。 

((<URL:https://twitter.com/makotokuwata/status/225806204390227968>))



Thank you for your consideration.

以上、ご検討のほどよろしくお願い致します。


=end



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