Module CCOpt

Options

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

map f o applies the function f to the element inside o, 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 comp o1 o2 compares two options o1 and o2, using custom comparators comp for the value. None is always assumed to be less than Some _.

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

equal p o1 o2 tests for equality between option types o1 and o2, using a custom equality predicate p.

val return : 'a -> 'a t

return x is a monadic return, that is return x = Some x.

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

o >|= f is the infix version of map.

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

flat_map f o is equivalent to map followed by flatten. Flip version of >>=.

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

bind o f is f v if o is Some v, None otherwise. Monadic bind.

since
3.0
val (>>=) : 'a t -> ('a -> 'b t) -> 'b t

o >>= f is the infix version of bind.

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

iter f o applies f to o. Iterate on 0 or 1 element.

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

fold f init o is f init x if o is Some x, or init if o is None. Fold on 0 or 1 element.

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

filter f o returns Some x if f (Some x) is true, or None if f (Some x) is false or if o is None. 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

exists f o returns true iff there exists an element for which the provided function f evaluates to true.

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

for_all f o returns true iff the provided function f 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 is None.

since
0.18
val value : 'a t -> default:'a -> 'a

value o ~default is similar to the Stdlib's Option.value and to get_or.

since
2.8
val get_exn : 'a t -> 'a

get_exn o returns x if o is Some x or fails if o is None.

raises Invalid_argument

if the option is None.

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

get_lazy default_fn o unwraps o, but if o is 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 ?handler 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 ?handler f x y is similar to wrap but for binary functions.

Applicative

val pure : 'a -> 'a t

pure x is an 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

f <$> o is like map f o.

Alternatives

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

or_ ~else_ o is o if o is Some _, else_ if o is None.

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

or_lazy ~else_ o is o if o is Some _, else_ () if o is None.

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

o1 <+> o2 is o1 if o1 is Some _, o2 if o1 is None.

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

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

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

flatten oo transforms Some x into x.

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

return_if b x applies Some or None depending on the boolean b. 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

Let operators on OCaml >= 4.08.0, nothing otherwise

since
2.8
include CCShimsMkLet_.S with type 'a t_let := 'a option
type 'a t_let
val let+ : 'a t_let -> ('a -> 'b) -> 'b t_let
val and+ : 'a t_let -> 'b t_let -> ('a * 'b) t_let
val let* : 'a t_let -> ('a -> 'b t_let) -> 'b t_let
val and* : 'a t_let -> 'b t_let -> ('a * 'b) t_let

Conversion and IO

val to_list : 'a t -> 'a list

to_list o returns [x] if o is Some x or the empty list [] if o is None.

val of_list : 'a list -> 'a t

of_list l returns Some x (x being the head of the list l), or None if l is the empty list.

val to_result : 'e -> 'a t -> ('a, 'e) Stdlib.result

to_result e o returns Ok x if o is Some x, or Error e if o is None.

since
1.2
val to_result_lazy : (unit -> 'e) -> 'a t -> ('a, 'e) Stdlib.result

to_result_lazy f o returns Ok x if o is Some x or Error f if o is None.

since
1.2
val of_result : ('a, _) Stdlib.result -> 'a t

of_result result returns an option from a result.

since
1.2
type 'a iter = ('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_iter : 'a t iter -> 'a t

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

since
3.0
val choice_seq : 'a t Stdlib.Seq.t -> 'a t

choice_seq seq works on Seq.t. It returns the first Some x occurring in seq, or None otherwise.

since
3.0
val to_gen : 'a t -> 'a gen

to_gen o is o as a gen. Some x is the singleton gen containing x and None is the empty gen.

val to_seq : 'a t -> 'a Stdlib.Seq.t

to_seq o is o as a sequence Seq.t. Some x is the singleton sequence containing x and None is the empty sequence. Same as Stdlib.Option.to_seq Renamed from to_std_seq since 3.0.

since
3.0
val to_iter : 'a t -> 'a iter

to_iter o returns an internal iterator, like in the library Iter.

since
2.8
val pp : 'a printer -> 'a t printer

pp ppf o pretty-prints option o using ppf.