val of_option : ('a, 'b) topt -> ('a, 'b) texnval compose : ('a, 'b) texn -> ('b, 'c) texn -> ('a, 'c) texnval commute : ('a * 'b, 'b * 'a) texnval identity : ('a, 'a) texnval subset : ('a -> bool) -> ('a, 'a) texnval element : compare:('a -> 'a -> bool) -> 'a -> ('a, unit) texnval singleton : ('a, 'a list) texnval cons : ('a * 'a list, 'a list) texnval nil : (unit, unit list) texnval some : ('a, 'a option) texnval none : (unit, unit option) texnval string : (char list, string) texnval safe_exn : ('a -> 'b) -> 'a -> 'bval int : (string, int) texnval bool : (string, bool) texnval fst : ('b, unit) texn -> ('a * 'b, 'a) texnval snd : ('b, unit) texn -> ('b * 'a, 'a) texn