package core_kernel

  1. Overview
  2. Docs
package core_kernel
Legend:
Library
Module
Module type
Parameter
Class
Class type

This module extends Base.Option with bin_io, quickcheck, and support for ppx_optional.

type 'a t = 'a Base.Option.t
include Bin_prot.Binable.S1 with type 'a t := 'a t
val bin_shape_t : Bin_prot.Shape.t -> Bin_prot.Shape.t
val bin_size_t : ('a, 'a t) Bin_prot.Size.sizer1
val bin_write_t : ('a, 'a t) Bin_prot.Write.writer1
val bin_read_t : ('a, 'a t) Bin_prot.Read.reader1
val __bin_read_t__ : ('a, int -> 'a t) Bin_prot.Read.reader1
val bin_writer_t : ('a, 'a t) Bin_prot.Type_class.S1.writer
val bin_reader_t : ('a, 'a t) Bin_prot.Type_class.S1.reader
val bin_t : ('a, 'a t) Bin_prot.Type_class.S1.t
include Typerep_lib.Typerepable.S1 with type 'a t := 'a t
val typename_of_t : 'a Typerep_lib.Typename.t -> 'a t Typerep_lib.Typename.t
include module type of struct include Base.Option end with type 'a t := 'a option
val compare : ('a -> 'a -> int) -> 'a option -> 'a option -> int
val hash_fold_t : (Base.Hash.state -> 'a -> Base.Hash.state) -> Base.Hash.state -> 'a option -> Base.Hash.state
include Base.Sexpable.S1 with type 'a t := 'a option
val t_of_sexp : (Sexplib0.Sexp.t -> 'a) -> Sexplib0.Sexp.t -> 'a option
val sexp_of_t : ('a -> Sexplib0.Sexp.t) -> 'a option -> Sexplib0.Sexp.t
include Base.Container.S1 with type 'a t := 'a option
val mem : 'a option -> 'a -> equal:('a -> 'a -> bool) -> bool

Checks whether the provided element is there, using equal.

val length : 'a option -> int
val is_empty : 'a option -> bool
val iter : 'a option -> f:('a -> unit) -> unit
val fold : 'a option -> init:'accum -> f:('accum -> 'a -> 'accum) -> 'accum

fold t ~init ~f returns f (... f (f (f init e1) e2) e3 ...) en, where e1..en are the elements of t

val fold_result : 'a option -> init:'accum -> f:('accum -> 'a -> ('accum, 'e) Base.Result.t) -> ('accum, 'e) Base.Result.t

fold_result t ~init ~f is a short-circuiting version of fold that runs in the Result monad. If f returns an Error _, that value is returned without any additional invocations of f.

val fold_until : 'a option -> init:'accum -> f:('accum -> 'a -> ('accum, 'final) Base__.Container_intf.Continue_or_stop.t) -> finish:('accum -> 'final) -> 'final

fold_until t ~init ~f ~finish is a short-circuiting version of fold. If f returns Stop _ the computation ceases and results in that value. If f returns Continue _, the fold will proceed. If f never returns Stop _, the final result is computed by finish.

Example:

type maybe_negative =
  | Found_negative of int
  | All_nonnegative of { sum : int }

(** [first_neg_or_sum list] returns the first negative number in [list], if any,
    otherwise returns the sum of the list. *)
let first_neg_or_sum =
  List.fold_until ~init:0
    ~f:(fun sum x ->
      if x < 0
      then Stop (Found_negative x)
      else Continue (sum + x))
    ~finish:(fun sum -> All_nonnegative { sum })
;;

let x = first_neg_or_sum [1; 2; 3; 4; 5]
val x : maybe_negative = All_nonnegative {sum = 15}

let y = first_neg_or_sum [1; 2; -3; 4; 5]
val y : maybe_negative = Found_negative -3
val exists : 'a option -> f:('a -> bool) -> bool

Returns true if and only if there exists an element for which the provided function evaluates to true. This is a short-circuiting operation.

val for_all : 'a option -> f:('a -> bool) -> bool

Returns true if and only if the provided function evaluates to true for all elements. This is a short-circuiting operation.

val count : 'a option -> f:('a -> bool) -> int

Returns the number of elements for which the provided function evaluates to true.

val sum : (module Base__.Container_intf.Summable with type t = 'sum) -> 'a option -> f:('a -> 'sum) -> 'sum

Returns the sum of f i for all i in the container.

val find : 'a option -> f:('a -> bool) -> 'a option

Returns as an option the first element for which f evaluates to true.

val find_map : 'a option -> f:('a -> 'b option) -> 'b option

Returns the first evaluation of f that returns Some, and returns None if there is no such element.

val to_list : 'a option -> 'a list
val to_array : 'a option -> 'a array
val min_elt : 'a option -> compare:('a -> 'a -> int) -> 'a option

Returns a minimum (resp maximum) element from the collection using the provided compare function, or None if the collection is empty. In case of a tie, the first element encountered while traversing the collection is returned. The implementation uses fold so it has the same complexity as fold.

val max_elt : 'a option -> compare:('a -> 'a -> int) -> 'a option
include Base.Equal.S1 with type 'a t := 'a option
val equal : 'a Base.Equal.equal -> 'a option Base.Equal.equal
include Base.Invariant.S1 with type 'a t := 'a option
val invariant : ('a -> unit) -> 'a option -> unit

Options form a monad, where return x = Some x, (None >>= f) = None, and (Some x >>= f) = f x.

include Base.Monad.S with type 'a t := 'a option
val (>>=) : 'a option -> ('a -> 'b option) -> 'b option

t >>= f returns a computation that sequences the computations represented by two monad elements. The resulting computation first does t to yield a value v, and then runs the computation returned by f v.

val (>>|) : 'a option -> ('a -> 'b) -> 'b option

t >>| f is t >>= (fun a -> return (f a)).

module Monad_infix = Base.Option.Monad_infix
val bind : 'a option -> f:('a -> 'b option) -> 'b option

bind t ~f = t >>= f

val return : 'a -> 'a option

return v returns the (trivial) computation that returns v.

val map : 'a option -> f:('a -> 'b) -> 'b option

map t ~f is t >>| f.

val join : 'a option option -> 'a option

join t is t >>= (fun t' -> t').

val ignore_m : 'a option -> unit option

ignore_m t is map t ~f:(fun _ -> ()). ignore_m used to be called ignore, but we decided that was a bad name, because it shadowed the widely used Caml.ignore. Some monads still do let ignore = ignore_m for historical reasons.

val all : 'a option list -> 'a list option
val all_unit : unit option list -> unit option

Like all, but ensures that every monadic value in the list produces a unit value, all of which are discarded rather than being collected into a list.

module Let_syntax = Base.Option.Let_syntax
val is_none : 'a option -> bool

is_none t returns true iff t = None.

val is_some : 'a option -> bool

is_some t returns true iff t = Some x.

val value_map : 'a option -> default:'b -> f:('a -> 'b) -> 'b

value_map ~default ~f is the same as function Some x -> f x | None -> default.

val map2 : 'a option -> 'b option -> f:('a -> 'b -> 'c) -> 'c option

map2 o f maps 'a option and 'b option to a 'c option using ~f.

val call : 'a -> f:('a -> unit) option -> unit

call x f runs an optional function ~f on the argument.

val value : 'a option -> default:'a -> 'a

value None ~default = default

value (Some x) ~default = x

val value_exn : ?here:Caml.Lexing.position -> ?error:Base.Error.t -> ?message:string -> 'a option -> 'a

value_exn (Some x) = x. value_exn None raises an error whose contents contain the supplied ~here, ~error, and message, or a default message if none are supplied.

val some : 'a -> 'a option
val both : 'a option -> 'b option -> ('a * 'b) option
val first_some : 'a option -> 'a option -> 'a option
val some_if : bool -> 'a -> 'a option
val merge : 'a option -> 'a option -> f:('a -> 'a -> 'a) -> 'a option

merge a b ~f merges together the values from a and b using f. If both a and b are None, returns None. If only one is Some, returns that one, and if both are Some, returns Some of the result of applying f to the contents of a and b.

val filter : 'a option -> f:('a -> bool) -> 'a option
val try_with : (unit -> 'a) -> 'a option

try_with f returns Some x if f returns x and None if f raises an exception. See Result.try_with if you'd like to know which exception.

val try_with_join : (unit -> 'a option) -> 'a option

try_with_join f returns the optional value returned by f if it exits normally, and None if f raises an exception.

val validate : none:unit Base.Validate.check -> some:'a Base.Validate.check -> 'a option Base.Validate.check
include Comparator.Derived with type 'a t := 'a t
type 'cmp comparator_witness
include Quickcheckable.S1 with type 'a t := 'a t
val quickcheck_generator : 'a Base_quickcheck.Generator.t -> 'a t Base_quickcheck.Generator.t
val quickcheck_observer : 'a Base_quickcheck.Observer.t -> 'a t Base_quickcheck.Observer.t
val quickcheck_shrinker : 'a Base_quickcheck.Shrinker.t -> 'a t Base_quickcheck.Shrinker.t
module Stable : sig ... end
module Optional_syntax : Optional_syntax.S1 with type 'a t := 'a t and type 'a value := 'a

You might think that it's pointless to have Optional_syntax on options because OCaml already has nice syntax for matching on options. The reason to have this here is that you might have, for example, a tuple of an option and some other type that supports Optional_syntax. Since Optional_syntax can only be opted into at the granularity of the whole match expression, we need this Optional_syntax support for options in order to use it for the other half of the tuple.

OCaml

Innovation. Community. Security.

GitHub Discord Twitter Peertube RSS
About
Changelog Releases Industrial Users Academic Users Why OCaml
Ecosystem
Packages Community Events OCaml Planet Jobs
Resources
Install OCaml Get Started Platform Tools Language Manual Standard Library API Books Exercises Papers OCaml Playground Logo
Policies
Carbon Footprint Governance Privacy Code of Conduct