A cardinal in Ruby 1.9 See https://github.com/raganwald/homoiconic/blob/master/2008-10-31/songs_of_the_cardinal.markdown

cardinal.rb

def cardinal_define(name, &proc_over_proc)
    self.class.send(:define_method, name) do |a_value, &a_proc|
        proc_over_proc.call(a_proc).call(a_value)
    end
end

cardinal_define(:maybe) do |a_proc|
    lambda { |a_value|
        a_proc.call(a_value) unless a_value.nil?
    }
end

maybe(1) do |x|
    x + 1
end
    #=> 2

maybe(nil) do |x|
    x + 1
end
    #=> nil