public static void BuildAndShow(String filename, Regex r)
{
Nfa nfa = r.MkNfa(new Nfa.NameSource());
Console.WriteLine(nfa);
Console.WriteLine("---");
Dfa dfa = nfa.ToDfa();
Console.WriteLine(dfa);
Console.WriteLine("Writing DFA graph to file " + filename);
dfa.WriteDot(filename);
Console.WriteLine();
}