class CharEnumerator
  include Enumerable
 
  def initialize(str)
    @str = str
    @idx = 0
  end
 
  def each(&block)
    while @idx < @str.length
      yield @str[@idx]
      @idx += 1
    end
  end
end
 
#### main ####
 
puts '***************'
CharEnumerator.new('abcdefghijklmn').each do |ch|
  puts ch
end
 
puts '***************'
### Enumerableをincludeすると、each以外にも便利なもAPIが使える
CharEnumerator.new('abcdefghijklmn').each_with_index do |ch, idx|
  puts "#{idx+1}文字目は#{ch}"
end
 
 

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