working prototype (config generation)

lib/puppet/parser/functions/pick_undef.rb

@@ -0,0 +1,15 @@
+module Puppet::Parser::Functions
+ newfunction(:pick_undef, :type => :rvalue, :doc => <<-EOS
+             This function is similar to pick_default, but will return or undefined values.
+EOS
+) do |args|
+   fail "Must receive at least one argument." if args.empty?
+   default = args.last
+   args = args[0..-2].compact
+#   args.delete(:undef)
+#   args.delete(:undefined)
+#   args.delete("")
+   args << default
+   return args[0]
+ end
+end