Extending an Enum type

[Antoon Pardon]

Hi, I am experimenting with writing an Earley Parser. Now I would like
to have the non-terminals from the grammer I am reading in, be
represented bye an enum like type. So that if the grammer contains the
following production: Term -> Term '+' Factor I can reprensent the right
hand side with a list that gets printed something like the following:
[<Non_Terminal.Term:1>, '+', <Non_Terminal.Factor:2>] I am a bit at a
loss right now on how to start. Can someone point me in the right
direction? -- Antoon Pardon