Feature #6687
Enumerable#with
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
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