type code = Elem of bool | Not | And | Or | Xor;;

let eval le =
        List. hd (List.fold_left (fun stack e ->
                                (match e with
                                    | Elem(b) ->
                                        b::stack
                                    | Not ->
                                        if List.length stack < 1 then failwith "Za malo argumentow dla not"
                                        else (not (List.hd stack))::(List.tl stack)
                                    | And ->
                                        if List.length stack < 2 then failwith "Za malo argumentow dla and"
                                        else ((List.hd stack) && (List.hd (List.tl stack)))::(List.tl (List.tl stack))
                                    | Or ->
                                        if List.length stack < 2 then failwith "Za malo argumentow dla or"
                                        else ((List.hd stack) || (List.hd (List.tl stack)))::(List.tl (List.tl stack))
                                    | Xor ->
                                        if List.length stack < 2 then failwith "Za malo argumentow dla xor"
                                        else ((List.hd stack) || (List.hd (List.tl stack)) || (not ((List.hd stack) && (List.hd (List.tl stack))))) ::(List.tl (List.tl stack))
                                    )
                    ) [] le);;

eval [Elem true];;
eval [Elem true; Not];;
eval [Elem true; Not; Elem false; Or; Elem true; Xor; Elem true; And];;
eval [Elem true; And];;
eval [Elem false; Elem true; Not; Elem false; Or; Elem true; Xor; Elem true; And];;