bool.rb

module Control
  def if(e1, e2)
     if self.isTrue? then e1 else e2 end
  end
  def if_(e1, e2)
    self.if(e1, e2).call
  end  
end

module Bool
  include Control
  def and(other)
    self.if(other, self)
  end
  def or(other)
    self.if(self, other)
  end
end

# 既存のクラスを拡張

class TrueClass
  include Bool
  def isTrue?
    if self == true then true else false end
  end
end

class FalseClass
  include Bool
  def isTrue?
    if self != false then true else false end
  end
end

class NilClass
  include Bool
  def isTrue?
    if self != nil then true else false end
  end
end

class String
  include Bool
  def isTrue?
    if self != "" then true else false end
  end
end

class Integer
  include Bool
  def isTrue?
    if self != 0 then true else false end
  end
end

class Array
  include Bool
  def isTrue?
    if not self.empty? then true else false end
  end
end