[Ruby] 便利な組み込みクラスのメソッド達（Enumerable編） ref: http://qiita.com/kidachi_/items/a00558cfb0a6a3e23f4b

file0.rb

> %w(Ruby Python Java).each_with_index do |value, key|
>   puts "#{key}: #{value}"
> end
0: Ruby
1: Python
2: Java

file1.rb

> %w(Ruby Python Java).reverse { |val| puts val }
=> ["Java", "Python", "Ruby"]

file10.rb

# 要素が全て整数ならtrue
> [1, 10, 100].all? {|v| v.is_a?(Integer)}
=> true
# 要素が全て文字列ならtrue
> [1, 10, 100].all? {|v| v.is_a?(String)}
=> false
> ["Ruby", "Python", "Java"].all? {|v| v.is_a?(String)}
=> true

file11.rb

# 正規表現にマッチする要素を取得
> %w(Ruby Python Java).grep(/y/)
=> ["Ruby", "Python"]

# 指定の型にマッチする要素を取得
> ["Ruby", "Python", "Java", 1, 10, 100].grep(String)
=> ["Ruby", "Python", "Java"]
> ["Ruby", "Python", "Java", 1, 10, 100].grep(Integer)
=> [1, 10, 100]

file12.rb

> %w(Ruby Python Java C Smalltalk Brainfuck).detect { |s| s.include?("y") }
=> "Ruby"

file13.rb

> %w(Ruby Python Java C Smalltalk Brainfuck).select { |s| s.include?("y") }
=> ["Ruby", "Python"]

file14.rb

> %w(Ruby Python Java C Smalltalk Brainfuck).reject { |s| s.include?("y") }
=> ["Java", "C", "Smalltalk", "Brainfuck"]

file15.rb

> %w(Ruby Python Java C Smalltalk Brainfuck).take(3)
=> ["Ruby", "Python", "Java"]

file16.rb

> %w(Ruby Python Java C Smalltalk Brainfuck).drop(3)
=> ["C", "Smalltalk", "Brainfuck"]

file17.rb

> %w(Ruby Python Java C Smalltalk Brainfuck).take_while { |s| s.include?("y") }
=> ["Ruby", "Python"]

file18.rb

> %w(Ruby Python Java C Smalltalk Brainfuck).drop_while { |s| s.include?("y") }
=> ["Java", "C", "Smalltalk", "Brainfuck"]

file19.rb

> [1, 2, 3, 4].inject(0) { |result, num| result + num }
=> 10    # 0 +1 + 2 + 3 + 4

file2.rb

> %w(Ruby Python Java C Smalltalk Brainfuck).each_slice 2 do |a, b|
>   p [a, b]
> end
["Ruby", "Python"]
["Java", "C"]
["Smalltalk", "Brainfuck"]

> %w(Ruby Python Java C Smalltalk Brainfuck).each_slice 4 do |a, b, c, d|
>   p [a, b, c, d]
> end
["Ruby", "Python", "Java", "C"]
["Smalltalk", "Brainfuck", nil, nil]    # 帳尻が合わなかった部分はnil

file20.rb

> [1, 2, 3, 4].inject { |result, num| result + num }
=> 10    # 1 + 2 + 3 + 4

file21.rb

> [1, 2, 3, 4].inject(:+)
=> 10
> [1, 2, 3, 4].inject(:*)
=> 24

file22.rb

> %w(Ruby Python Java).each_with_object({}) do |name, result|
>   p result
>   result[name] = name.length
> end
{}
{"Ruby"=>4}
{"Ruby"=>4, "Python"=>6}
=> {"Ruby"=>4, "Python"=>6, "Java"=>4}

file23.rb

> ["Ruby", 1.0, "Python", 1000, 2.5, "Java"].group_by { |v| v.class }
=> {String=>["Ruby", "Python", "Java"], Float=>[1.0, 2.5], Fixnum=>[1000]}

file24.rb

> ["Ruby", 1.0, "Python", 1000, 2.5, "Java"].partition { |v| v.is_a?(String) }
=> [["Ruby", "Python", "Java"], [1.0, 1000, 2.5]]

file25.rb

> range = (1..5)
> range.max
=> 5
> range.min
=> 1
> range.minmax
=> [1, 5]

file26.rb

> lang = %w(Ruby Python Java C)
> lang.min_by { |s| s.length }
=> "C"
> lang.max_by { |s| s.length }
=> "Python"
> lang.minmax_by { |s| s.length }
=> ["C", "Python"]

file27.rb

> lang = %w(Ruby Python Java C)
# アルファベット順
> lang.sort
=> ["C", "Java", "Python", "Ruby"]
# 要素の長さ(1)
> lang.sort { |a, b| a.length <=> b.length }
=> ["C", "Java", "Ruby", "Python"]
# 要素の長さ(2)
> lang.sort_by { |str| str.length }
=> ["C", "Java", "Ruby", "Python"]

file3.rb

> %w(Ruby Python Java C Smalltalk Brainfuck).each_cons 2 do |a, b|
>   p [a, b]
> end
["Ruby", "Python"]
["Python", "Java"]
["Java", "C"]
["C", "Smalltalk"]
["Smalltalk", "Brainfuck"]

file4.rb

> %w(Ruby Python Java).map { |s| s.upcase }
=> ["RUBY", "PYTHON", "JAVA"]

file5.rb

> %w(Ruby Python Java).each {|s| p s.upcase}
"RUBY"
"PYTHON"
"JAVA"
=> ["Ruby", "Python", "Java"]

file5.txt

> %w(Ruby Python Java).each {|s| p s.upcase}
"RUBY"
"PYTHON"
"JAVA"
=> ["Ruby", "Python", "Java"]

file6.rb

> [true, true, true].all?
=> true
> [true, true, false].all?
=> false

file7.rb

> [false, false, false].none?
=> true
> [true, true, false].none?
=> false

file8.rb

> [true, true, false].any?
=> true
> [false, false, false].any?
=> false

file9.rb

> [false, false, true].one?
=> true
> [false, false, false].one?
=> false
> [false, true, true].one?
=> false