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Feature #6687

Enumerable#with

Added by merborne (kyo endo) almost 8 years ago. Updated over 2 years ago.

Status:
Open
Priority:
Normal
Assignee:
-
Target version:
-
[ruby-core:46105]

Description

=begin
Let me propose Enumerable#with for an alias of Enumerable#each_with_object or replace of it.

Enumerable#each_with_objectのエイリアス、またはその置き換えとして、Enumerable#withを提案します。

##Reason

##理由

When you create a hash using Enumerable#inject, you should ensure that the block return the hash.

Enumerable#injectを使ってハッシュを生成するときには、ブロックの返り値としてハッシュが返ることを保証する必要があります。

words.inject(Hash.new(0)) { |h, word| h[word] += 1; h } # => {"You"=>3, "say"=>10, "Yes"=>1, "I"=>7, "No"=>1, "Stop"=>1, "and"=>2, "Go"=>1, "go"=>2, "Oh"=>1, "no"=>1, "Goodbye"=>2, "Hello"=>2, "hello"=>5, "don"=>2, "t"=>2, "know"=>2, "why"=>2, "you"=>2, "goodbye"=>1}

Many rubyists, however, hate this, and there are many discussions for it.

しかし、これを嫌うRubyistは多く、ネット上でその改善についての議論をしばしば見掛けます。

Feature #5662: inject-accumulate, or Haskell's mapAccum* - ruby-trunk - Ruby Issue Tracking System http://bugs.ruby-lang.org/issues/5662

Ruby inject with intial being a hash - Stack Overflow http://stackoverflow.com/questions/9434162/ruby-inject-with-intial-being-a-hash

Enumerable#each_with_object is often presented for one of the best solutions for it.

そしてその有力な解決策として、Enumerable#each_with_objectが提示されてきました。

words.each_with_object(Hash.new(0)) { |word, h| h[word] += 1 } # => {"You"=>3, "say"=>10, "Yes"=>1, "I"=>7, "No"=>1, "Stop"=>1, "and"=>2, "Go"=>1, "go"=>2, "Oh"=>1, "no"=>1, "Goodbye"=>2, "Hello"=>2, "hello"=>5, "don"=>2, "t"=>2, "know"=>2, "why"=>2, "you"=>2, "goodbye"=>1}

However, each_with_object is still unfamiliar and then not used frequently. The biggest reason, I think, is its lengthy name.

しかし、その有用性にも拘らず、依然としてeach_with_objectの知名度および利用頻度は低いと思われます。そして、その原因は、その名前の長さにあると考えます。

each_with_object is the 39th longest-name method among 754 at Ruby 1.9.3, based on following calculation;

以下の演算により、Ruby1.9.3の環境下でeach_with_objectは、754件中39番目に長い名前のメソッドであることが分かりました。

methods = Module.constants.flat_map do |c|
  next [] if c == :Gem
  k = Module.const_get(c)
  k.methods(false) + k.instance_methods(false) rescue []
end.uniq.reject { |m| "#{m}".start_with? '_deprecated' }.sort_by { |m| -m.size }

methods.size # => 754
methods.index(:each_with_object) # => 39

puts methods.take(100).group_by(&:size).to_a

The output is here.

出力です。

26
protected_instance_methods
instance_variable_defined?
25
protected_method_defined?
24
private_instance_methods
23
class_variable_defined?
public_instance_methods
define_singleton_method
private_method_defined?
22
singleton_method_added
public_instance_method
public_method_defined?
21
instance_variable_get
instance_variable_set
remove_class_variable
20
private_class_method
repeated_combination
repeated_permutation
compare_by_identity?
19
respond_to_missing?
abort_on_exception=
public_class_method
compare_by_identity
18
undefine_finalizer
instance_variables
abort_on_exception
class_variable_get
class_variable_set
relative_path_from
17
internal_encoding
external_encoding
default_internal=
default_external=
protected_methods
singleton_methods
ascii_compatible?
16
global_variables
executable_real?
initialize_clone
each_with_object   # <= Here!
require_relative
private_constant
default_external
included_modules
instance_methods
define_finalizer
default_internal
15
private_methods
fixed_encoding?
class_variables
instance_method
each_with_index
public_constant
garbage_collect
source_location
valid_encoding?
singleton_class
world_writable?
local_variables
world_readable?
method_defined?
14
readable_real?
locale_charmap
const_defined?
collect_concat
initialize_dup
add_trace_func
close_on_exec=
close_on_exec?
named_captures
set_trace_func
write_nonblock
writable_real?
each_codepoint
force_encoding
public_methods
13
const_missing
each_filename
default_proc=
set_backtrace
public_method
read_nonblock
instance_exec
absolute_path
count_objects
instance_eval
12
marshal_load
reverse_each
exclude_end?
instance_of?
make_symlink
set_encoding
block_given?
default_proc
slice_before
marshal_dump
11
rationalize
realdirpath
each_object
expand_path
with_object

This result shows that methods which has 15+ name length is mostly for reflection or for special purpose. each_with_object is a general purpose method, the name should be shorter.

このリストから分かることは、長さ15を超えるメソッドはその大半がリフレクション用か特殊目的用のものであるという事実です。each_with_objectはより汎用的なメソッドですから、その名前はもっと短くあるべきと考えます。現状の長さは、そのメソッドを無きものにしています。

I propose Enumerable#with for it. a word object in each_with_object is obvious and not necessary to spcify the purpose, because all data in Ruby is object. Also, a word each in each_with_object is not essential, then omittable in view of the fact that it is called to Enumerable object. I think that a word with still works for describing the same of each_with_object.

そこでEnumerable#withを提案します。まず、Rubyで扱われるデータはすべてオブジェクトですから、each_with_objectにおけるobjectは自明であり不要と考えます。次に、Enumerableオブジェクトに対するメソッド呼び出しという点から見て、eachも必須のものとは言えず、削除可能と考えます。そして残ったwithで十分にその目的、つまりEnumerableな要素を任意のオブジェクトと共に操作する、を意図できていると考えます。

Lastly, following is examples with Enumerable#with

最後に、Enumerable#withを使った例を示します。

Enumerable.send(:alias_method, :with, :each_with_object)

words.with(Hash.new(0)) { | word, h| h[word] += 1 } # => {"You"=>3, "say"=>10, "Yes"=>1, "I"=>7, "No"=>1, "Stop"=>1, "and"=>2, "Go"=>1, "go"=>2, "Oh"=>1, "no"=>1, "Goodbye"=>2, "Hello"=>2, "hello"=>5, "don"=>2, "t"=>2, "know"=>2, "why"=>2, "you"=>2, "goodbye"=>1}

[*1..10].with(5).map(&:*) # => [5, 10, 15, 20, 25, 30, 35, 40, 45, 50]

['ruby', 'python', 'haskell'].with('ist').map(&:+) # => ["rubyist", "pythonist", "haskellist"]

Thank you for your consideration.

ご検討の程よろしくお願い致します。

=end


Related issues

Related to Ruby master - Feature #7384: Rename #each_with_object to #each_withOpenActions
Related to Ruby master - Feature #7340: 'each_with' or 'into' alias for 'each_with_object'OpenActions

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