Option(3o) OCaml library Option(3o)
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 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 val-
ues 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 .
OCamldoc 2023-02-12 Option(3o)
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