exception Type_error of string * t
exception Undefined of string * t
val typerr : string -> t -> 'a
val combine : t -> t -> t
val index : int -> t -> t
val map : ( t -> t ) -> t -> t
val to_assoc : t -> (t * t) list
val to_option : ( t -> 'a ) -> t -> 'a option
val to_bool_option : t -> bool option
val to_number : t -> float
val to_number_option : t -> float option
val to_float : t -> float
val to_float_option : t -> float option
val to_int_option : t -> int option
val to_list : t -> t list
val to_string : t -> string
val to_string_option : t -> string option