[#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:46166] [ruby-trunk - Feature #6684] Object#do

From: "nobu (Nobuyoshi Nakada)" <nobu@...>
Date: 2012-07-04 07:17:11 UTC
List: ruby-core #46166
Issue #6684 has been updated by nobu (Nobuyoshi Nakada).


=begin
(({something.do do end})) seems messy a little.

(({something.do do end}))というのはどうにも…。
=end

----------------------------------------
Feature #6684: Object#do
https://bugs.ruby-lang.org/issues/6684#change-27786

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


=begin
#Object#do
This is my first post.

初めての投稿です。よろしくお願いします。

Let me propose a new method `Object#do`.

次のような実装の`Object#do`を提案します。

    class Object
      def do(*args, &blk)
        yield(self, *args)
      end
    end

`do` encapsulate a sequencial procedure into a block. It makes some temporal variables to be block local and enhance code readability. I might say that `do` is an Object#tap with block result, or is Array#map for one item.

`do`はオブジェクトに対する一連の処理をブロック内に閉じ込めます。それによって、一時変数のブロック内への局所化、コードの可読性向上を実現します。結果を返すObject#tap、単項版Array#mapと見ることができます。

##Usage

    # calculate average and standard deviation for list
    #
    # without `do`
    scores = [56, 87, 49, 75, 90, 63, 65]
    scores.inject(:+) / scores.size # => 69
    
    avg = scores.inject(:+) / scores.size
    sigmas = scores.map { |n| (avg - n)**2 }
    sd = Math.sqrt(sigmas.inject(:+) / scores.size) # => 14.247806848775006
    
    # with `do`
    avg = [56, 87, 49, 75, 90, 63, 65].do { |s| s.inject(:+) / s.size } # => 69
    
    sd = scores.do { |s|
      avg = s.inject(:+) / s.size
      sigmas = s.map { |n| (avg - n)**2 }
      Math.sqrt(sigmas.inject(:+) / s.size)
    }
    sd # => 14.247806848775006
    
    # create a hash from a set of lists
    #
    # without `do`
    h = Hash[ [:a, :b, :c].zip([1, 2, 3]) ] # => {:a=>1, :b=>2, :c=>3}
    
    # with `do`
    h = [:a, :b, :c].zip([1,2,3]).do { |arr| Hash[arr] } # => {:a=>1, :b=>2, :c=>3}
    
    
    # sum of array using recursion
    #
    # without `do`
    def sum(lst, mem=0)
      return mem if lst.empty?
      sum(lst.drop(1), mem+lst.first)
    end
    
    sum [*1..5], 5 # => 20
    
          # or
    
    def sum(lst, mem=0)
      return mem if lst.empty?
      fst, *tail = lst
      sum(tail, mem+fst)
    end
    
    # with `do`
    def sum(lst, mem=0)
      return mem if lst.empty?
      lst.do { |fst, *tail| sum(tail, mem+fst) }
    end
    
    sum2 [*1..5], 5 # => 20

BasicObject#instance_eval works for the above, but it not appropriate for them.

同様の目的はBasicObject#instance_evalでも実現できますが、この種の一般的演算には適さないと考えます。


Thank you for your consideration.
=end


-- 
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