Rubyists are cool! is another example of Ruby metaprogramming.

program.rb

class Person < Struct.new(:name, :programs_ruby)
  def cool_feeling
    puts "#{name} is definietly cool!"
  end
end

class People < Struct.new(:list)
    
  def who
    SelectQuery.new(self)
  end
  
  def are
    OutputQuery.new(self)
  end
end

class SelectQuery
  def initialize(people)
    @people = people
  end
  
  def method_missing(id, *args)
    @people.list.select! do |p|
      method_name = id.to_s.gsub!("_", "s_")
      p.send(method_name, *args)
    end
    
    @people
  end
end

class OutputQuery
  def initialize(people)
    @people = people
  end
  
  def method_missing(id, *args)
    @people.list.each { |p| p.send("#{id}_feeling") }
    
    @people
  end
end

people = People.new([
  Person.new("David Heinemeier Hansson", true),
  Person.new("Bill Gates", false),  
  Person.new("Satish Talim", true),
  Person.new("Samnang Chhun", true)
])

people.who.program_ruby.are.cool