Module Core_kernel__.Nothing
type t
=
Having
[@@deriving enumerate]
may seem strange due to the fact that generatedval all : t list
is the empty list, so it seems like it could be of no use.This may be true if you always expect your type to be
Nothing.t
, but[@@deriving enumerate]
can be useful if you have a type which you expect to change over time. For example, you may have a program which has to interact with multiple servers which are possibly at different versions. It may be useful in this program to have a variant type which enumerates the ways in which the servers may differ. When all the servers are at the same version, you can change this type toNothing.t
and code which uses an enumeration of the type will continue to work correctly.This is a similar issue to the identifiability of
Nothing.t
. As discussed below, another case where[@deriving enumerate]
could be useful is when this type is part of some larger type.
val hash_fold_t : Base.Hash.state -> t -> Base.Hash.state
val hash : t -> Base.Hash.hash_value
val all : t Core_kernel__.Import.list
val unreachable_code : t -> _
Because there are no values of type
Nothing.t
, a piece of code that has a value of typeNothing.t
must be unreachable. In such an unreachable piece of code, one can useunreachable_code
to give the code whatever type one needs. For example:let f (r : (int, Nothing.t) Result.t) : int = match r with | Ok i -> i | Error n -> Nothing.unreachable_code n ;;
Note that the compiler knows that
Nothing.t
is uninhabited, hence this will type without warning:let f (Ok i : (int, Nothing.t) Result.t) = i
It may seem weird that this is identifiable, but we're just trying to anticipate all the contexts in which people may need this. It would be a crying shame if you had some variant type involving Nothing.t
that you wished to make identifiable, but were prevented for lack of Identifiable.S
here.
Obviously, of_string
and t_of_sexp
will raise an exception.
include Core_kernel.Identifiable.S with type t := t
include Bin_prot.Binable.S with type t := t
include Bin_prot.Binable.S_only_functions with type t := t
val bin_size_t : t Bin_prot.Size.sizer
val bin_write_t : t Bin_prot.Write.writer
val bin_read_t : t Bin_prot.Read.reader
val __bin_read_t__ : (int -> t) Bin_prot.Read.reader
This function only needs implementation if
t
exposed to be a polymorphic variant. Despite what the type reads, this does *not* produce a function after reading; instead it takes the constructor tag (int) before reading and reads the rest of the variantt
afterwards.
val bin_shape_t : Bin_prot.Shape.t
val bin_writer_t : t Bin_prot.Type_class.writer
val bin_reader_t : t Bin_prot.Type_class.reader
val bin_t : t Bin_prot.Type_class.t
val hash_fold_t : Base.Hash.state -> t -> Base.Hash.state
val hash : t -> Base.Hash.hash_value
include Ppx_sexp_conv_lib.Sexpable.S with type t := t
val t_of_sexp : Sexplib0.Sexp.t -> t
val sexp_of_t : t -> Sexplib0.Sexp.t
include Core_kernel.Identifiable.S_common with type t := t
val compare : t -> t -> Core_kernel__.Import.int
val hash_fold_t : Base.Hash.state -> t -> Base.Hash.state
val hash : t -> Base.Hash.hash_value
val sexp_of_t : t -> Ppx_sexp_conv_lib.Sexp.t
include Core_kernel__.Import.Stringable.S with type t := t
include Core_kernel__.Import.Pretty_printer.S with type t := t
val pp : Base.Formatter.t -> t -> unit
include Core_kernel.Comparable.S_binable with type t := t
include Core_kernel__.Comparable_intf.S_common
include Base.Comparable.S
include Base__.Comparable_intf.Polymorphic_compare
val ascending : t -> t -> int
ascending
is identical tocompare
.descending x y = ascending y x
. These are intended to be mnemonic when used likeList.sort ~compare:ascending
andList.sort ~cmp:descending
, since they cause the list to be sorted in ascending or descending order, respectively.
val descending : t -> t -> int
val between : t -> low:t -> high:t -> bool
between t ~low ~high
meanslow <= t <= high
val clamp_exn : t -> min:t -> max:t -> t
clamp_exn t ~min ~max
returnst'
, the closest value tot
such thatbetween t' ~low:min ~high:max
is true.Raises if
not (min <= max)
.
val clamp : t -> min:t -> max:t -> t Base.Or_error.t
include Base.Comparator.S with type t := t
val comparator : (t, comparator_witness) Base.Comparator.comparator
include Base__.Comparable_intf.Validate with type t := t
val validate_lbound : min:t Base.Maybe_bound.t -> t Base.Validate.check
val validate_ubound : max:t Base.Maybe_bound.t -> t Base.Validate.check
val validate_bound : min:t Base.Maybe_bound.t -> max:t Base.Maybe_bound.t -> t Base.Validate.check
module Replace_polymorphic_compare : Core_kernel__.Comparable_intf.Polymorphic_compare with type t := t
include Core_kernel__.Comparable_intf.Map_and_set_binable with type t := t with type comparator_witness := comparator_witness
include Core_kernel.Comparator.S with type t := t
val comparator : (t, comparator_witness) Core_kernel.Comparator.comparator
module Map : Core_kernel.Map.S_binable with type Key.t = t with type Key.comparator_witness = comparator_witness
module Set : Core_kernel.Set.S_binable with type Elt.t = t with type Elt.comparator_witness = comparator_witness
include Core_kernel.Hashable.S_binable with type t := t
val hash_fold_t : Base.Hash.state -> t -> Base.Hash.state
val hash : t -> Base.Hash.hash_value
val hashable : t Core_kernel.Hashtbl.Hashable.t
module Table : Core_kernel.Hashtbl.S_binable with type key = t
module Hash_set : Core_kernel.Hash_set.S_binable with type elt = t
module Hash_queue : Core_kernel.Hash_queue.S with type key = t
module Stable : sig ... end