type 'a t = | Exact of string| Output| Pretty of 'a| Unreachable
val sexp_of_t :
('a -> Ppx_sexp_conv_lib.Sexp.t) ->
'a t ->
Ppx_sexp_conv_lib.Sexp.tval compare : ('a -> 'a -> int) -> 'a t -> 'a t -> intval map_pretty : 'a t -> f:('a -> 'b) -> 'b t