| M.Not x -> "not " ^ txt_boole x
| M.And (x, y) -> "(" ^ txt_boole x ^ " and " ^ txt_boole y ^ ")"
| M.Or (x, y) -> "(" ^ txt_boole x ^ " or " ^ txt_boole y ^ ")"
| M.Not x -> "not " ^ txt_boole x
| M.And (x, y) -> "(" ^ txt_boole x ^ " and " ^ txt_boole y ^ ")"
| M.Or (x, y) -> "(" ^ txt_boole x ^ " or " ^ txt_boole y ^ ")"