Module CCOpt

Options

type +'a t = 'a option
val map : ('a -> 'b) -> 'a t -> 'b t

Transform the element inside, if any.

val map_or : default:'b -> ('a -> 'b) -> 'a t -> 'b

map_or ~default f o is f x if o = Some x, default otherwise.

since
0.16
val map_lazy : (unit -> 'b) -> ('a -> 'b) -> 'a t -> 'b

map_lazy default_fn f o if f o if o = Some x, default_fn () otherwise.

since
1.2
val is_some : _ t -> bool

is_some (Some x) returns true otherwise it returns false.

val is_none : _ t -> bool

is_none None returns true otherwise it returns false.

since
0.11
val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int

Compare two options, using custom comparators for the value. None is always assumed to be less than Some _.

val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool

Test for equality between option types using a custom equality predicat.

val return : 'a -> 'a t

Monadic return, that is return x = Some x.

val (>|=) : 'a t -> ('a -> 'b) -> 'b t

Infix version of map.

val (>>=) : 'a t -> ('a -> 'b t) -> 'b t

Monadic bind.

val flat_map : ('a -> 'b t) -> 'a t -> 'b t

Flip version of >>=.

val map2 : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t

map2 f o1 o2 maps 'a option and 'b option to a 'c option using f.

val iter : ('a -> unit) -> 'a t -> unit

Iterate on 0 or 1 element.

val fold : ('a -> 'b -> 'a) -> 'a -> 'b t -> 'a

Fold on 0 or 1 element.

val filter : ('a -> bool) -> 'a t -> 'a t

Filter on 0 or 1 element.

since
0.5
val if_ : ('a -> bool) -> 'a -> 'a option

if_ f x is Some x if f x, None otherwise.

since
0.17
val exists : ('a -> bool) -> 'a t -> bool

Return true iff there exists an element for which the provided function evaluates to true.

since
0.17
val for_all : ('a -> bool) -> 'a t -> bool

Return true iff the provided function evaluates to true for all elements.

since
0.17
val get_or : default:'a -> 'a t -> 'a

get_or ~default o extracts the value from o, or returns default if o = None.

since
0.18
val get_exn : 'a t -> 'a

Open the option, possibly failing if it is None.

raises Invalid_argument

if the option is None.

val get_lazy : (unit -> 'a) -> 'a t -> 'a

get_lazy default_fn x unwraps x, but if x = None it returns default_fn () instead.

since
0.6.1
val sequence_l : 'a t list -> 'a list t

sequence_l [x1; x2; ...; xn] returns Some [y1;y2;...;yn] if every xi is Some yi. Otherwise, if the list contains at least one None, the result is None.

val wrap : ?⁠handler:(exn -> bool) -> ('a -> 'b) -> 'a -> 'b option

wrap f x calls f x and returns Some y if f x = y. If f x raises any exception, the result is None. This can be useful to wrap functions such as Map.S.find.

parameter handler

the exception handler, which returns true if the exception is to be caught.

val wrap2 : ?⁠handler:(exn -> bool) -> ('a -> 'b -> 'c) -> 'a -> 'b -> 'c option

wrap2 f x y is similar to wrap but for binary functions.

Applicative

val pure : 'a -> 'a t

Alias to return.

val (<*>) : ('a -> 'b) t -> 'a t -> 'b t

f <*> (Some x) returns Some (f x) and f <*> None returns None.

val (<$>) : ('a -> 'b) -> 'a t -> 'b t

Like map.

Alternatives

val or_ : else_:'a t -> 'a t -> 'a t

or_ ~else_ a is a if a is Some _, else_ otherwise.

since
1.2
val or_lazy : else_:(unit -> 'a t) -> 'a t -> 'a t

or_lazy ~else_ a is a if a is Some _, else_ () otherwise.

since
1.2
val (<+>) : 'a t -> 'a t -> 'a t

a <+> b is a if a is Some _, b otherwise.

val choice : 'a t list -> 'a t

choice returns the first non-None element of the list, or None.

val flatten : 'a t t -> 'a t

flatten transforms Some x into x.

since
2.2
val return_if : bool -> 'a -> 'a t

Apply Some or None depending on a boolean. More precisely, return_if false x is None, and return_if true x is Some x.

since
2.2

Infix Operators

since
0.16
module Infix : sig ... end

Conversion and IO

val to_list : 'a t -> 'a list
val of_list : 'a list -> 'a t

Head of list, or None.

val to_result : 'e -> 'a t -> ('a, 'e) Result.result
since
1.2
val to_result_lazy : (unit -> 'e) -> 'a t -> ('a, 'e) Result.result
since
1.2
val of_result : ('a, _) Result.result -> 'a t
since
1.2
type 'a sequence = ('a -> unit) -> unit
type 'a gen = unit -> 'a option
type 'a printer = Stdlib.Format.formatter -> 'a -> unit
type 'a random_gen = Stdlib.Random.State.t -> 'a
val random : 'a random_gen -> 'a t random_gen
val choice_seq : 'a t sequence -> 'a t

choice_seq s is similar to choice, but works on sequences. It returns the first Some x occurring in s, or None otherwise.

since
0.13
val to_gen : 'a t -> 'a gen
val to_seq : 'a t -> 'a sequence
val pp : 'a printer -> 'a t printer