Option(3)

NAME
Option - Option values.

Module
Module Option

Documentation

Module Option
 : sig end

Option values.

Option values explicitly indicate the presence or absence of a value.

Since 4.08

  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

Raises Invalid_argument otherwise.

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) is 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.

  Predicates and comparisons

val is_none : 'a option -> bool

is_none o is true iff o is None .

val is_some : 'a option -> bool

is_some o is true iff o is Some o .

val equal : ('a -> 'a -> bool) -> 'a option -> 'a option -> bool

equal eq o0 o1 is true iff 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.

  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 .