DFA.Transition.fs

module DFA =

    let rec nextState current token =
        match current.Transitions.TryGetValue token with
        | true, state -> state
        | _ ->
            let rec loop current next =
                if Set.isEmpty current then getState next else
                    let min = Set.minElement current
                    let current = Set.remove min current
                    match min with
                    | NFA.Branch br ->
                        loop (current.Add(br.x).Add(br.y)) next
                    | NFA.Read (_, f, n) ->
                        if f token
                        then loop current (next.Add n)
                        else loop current next
                    | NFA.Match ->
                        loop current next
            let next = loop current.States Set.empty
            current.Transitions.[token] <- next
            next