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|
(**************************************************************************)
(* *)
(* OCaml *)
(* *)
(* The OCaml programmers *)
(* *)
(* Copyright 2018 Institut National de Recherche en Informatique et *)
(* en Automatique. *)
(* *)
(* All rights reserved. This file is distributed under the terms of *)
(* the GNU Lesser General Public License version 2.1, with the *)
(* special exception on linking described in the file LICENSE. *)
(* *)
(**************************************************************************)
(** Option values.
Option values explicitly indicate the presence or absence of a value.
@since 4.08 *)
(** {1:options Options} *)
type 'a t = 'a option = None | Some of 'a (**)
(** The type for option values. Either [None] or a value [Some v]. *)
val none : 'a option
(** [none] is [None]. *)
val some : 'a -> 'a option
(** [some v] is [Some v]. *)
val value : 'a option -> default:'a -> 'a
(** [value o ~default] is [v] if [o] is [Some v] and [default] otherwise. *)
val get : 'a option -> 'a
(** [get o] is [v] if [o] is [Some v] and raise otherwise.
@raise Invalid_argument if [o] is [None]. *)
val bind : 'a option -> ('a -> 'b option) -> 'b option
(** [bind o f] is [f v] if [o] is [Some v] and [None] if [o] is [None]. *)
val join : 'a option option -> 'a option
(** [join oo] is [Some v] if [oo] is [Some (Some v)] and [None] otherwise. *)
val map : ('a -> 'b) -> 'a option -> 'b option
(** [map f o] is [None] if [o] is [None] and [Some (f v)] if [o] is [Some v]. *)
val fold : none:'a -> some:('b -> 'a) -> 'b option -> 'a
(** [fold ~none ~some o] is [none] if [o] is [None] and [some v] if [o] is
[Some v]. *)
val iter : ('a -> unit) -> 'a option -> unit
(** [iter f o] is [f v] if [o] is [Some v] and [()] otherwise. *)
(** {1:preds Predicates and comparisons} *)
val is_none : 'a option -> bool
(** [is_none o] is [true] if and only if [o] is [None]. *)
val is_some : 'a option -> bool
(** [is_some o] is [true] if and only if [o] is [Some o]. *)
val equal : ('a -> 'a -> bool) -> 'a option -> 'a option -> bool
(** [equal eq o0 o1] is [true] if and only if [o0] and [o1] are both [None]
or if they are [Some v0] and [Some v1] and [eq v0 v1] is [true]. *)
val compare : ('a -> 'a -> int) -> 'a option -> 'a option -> int
(** [compare cmp o0 o1] is a total order on options using [cmp] to compare
values wrapped by [Some _]. [None] is smaller than [Some _] values. *)
(** {1:convert Converting} *)
val to_result : none:'e -> 'a option -> ('a, 'e) result
(** [to_result ~none o] is [Ok v] if [o] is [Some v] and [Error none]
otherwise. *)
val to_list : 'a option -> 'a list
(** [to_list o] is [[]] if [o] is [None] and [[v]] if [o] is [Some v]. *)
val to_seq : 'a option -> 'a Seq.t
(** [to_seq o] is [o] as a sequence. [None] is the empty sequence and
[Some v] is the singleton sequence containing [v]. *)
|
