Create a simple FSM model

FiniteStateMachine.fs

// A representation from http://stackoverflow.com/questions/5840292/automata-in-ocaml

type FiniteStateMachine<'State, 'Input> = {
  Initial    : 'State;
  Final      : 'State -> bool;
  Transition : 'Input -> 'State -> 'State;
}

type IntegerKind =
  | Odd
  | Even

let odd = {
  Initial    = Even; 
  Final      = (function Odd -> true | _ -> false);
  Transition = (function 
                | "next" -> (function Even -> Odd | Odd -> Even)
                |  _  -> id);
}

let product a b = {
  Initial    = (a.Initial, b.Initial);
  Final      = (fun (x, y) -> a.Final x && b.Final y);
  Transition = (fun c (x, y) -> a.Transition c x, b.Transition c y);
}