Module `Caml.Option`

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) Stdlib.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.