Module Option

module Option: sig .. end

Option values.

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

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 raise 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) if o is Some v.

val product : 'a option -> 'b option -> ('a * 'b) option

product o0 o1 is Some (v0, v1) if o0 is Some v0 and o1 is Some v1 and None otherwise.

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.

val blend : ('a -> 'a -> 'a) -> 'a option -> 'a option -> 'a option

blend f o1 o2 is o1 if o2 is None, o2 if o1 is None, and Some (f v1 v2) if o1 is Some v1 and o2 is Some v2.

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

for_all p behaves like List.for_all p on a list of zero or one element:

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

exists p behaves like List.exists p on a list of zero or one element:

val is_none : 'a option -> bool

is_none o is true if and only if o is None.

val is_some : 'a option -> bool

is_some o is true if and only if o is Some o.

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

equal eq o0 o1 is true if and only if 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.

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.

module Syntax: sig .. end

Binding operators.