Iterator and Template Method

I&T.rb

class List
  include Enumerable

  def each
    yield 1
    yield 2
  end
	  
  #...
end

a = List.new

# e is a iterator here.
p e = a.to_enum
p e.next
p e.next
# When the position reached at the end, StopIteration is raised.
# p e.next

# All the following methods are “Visitors” defined in Enumerable Module
p a.partition {|it| it>1}
p a.collect {|it| it+1}
# ...

IT.rb

class List
  include Enumerable

  def each
    yield 1
    yield 2
  end
	  
  #...
end

a = List.new

# e is a iterator here.
p e = a.to_enum
p e.next
p e.next
# When the position reached at the end, StopIteration is raised.
# p e.next

# All the following methods are template methods defined in Enumerable Module
p a.partition {|it| it>1}
p a.collect {|it| it+1}
# ...