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