title: How to define optional parameters in Puppet::Functions
body: <p>I want to create a puppet ruby function with <code>Puppet::Functions.create_function</code>. Here i define some parameters. Some of this should be optional or should have default values.</p>
  
  <pre><code>Puppet::Functions.create_function(:'foo') do
    dispatch :bar do
      param 'String', :param_1
      param 'String', :param_2
      param 'String', :param_3
  
      def bar(a,b,c)
        puts "#{a} - #{b} - #{c}"
      end
  end
  </code></pre>
  
  <p>param_1 and param_3 should be optional. Is there a way to do this?</p>