module Option: Option
type 'a
t = 'a option
include Container.S1
Options form a monad, where
return x = Some x
None >>= f = None
Some x >>= f = f x
include Monad.S
include Sexpable.S1
val is_none : 'a t -> bool
is_none t
returns true iff t = None.
val is_some : 'a t -> bool
is_some t
returns true iff t = Some x.
val value_map : 'a t -> default:'b -> f:('a -> 'b) -> 'b
value_map None ~default ~f
= default
value_map (Some x) ~default ~f
= f x
val map : 'a t -> f:('a -> 'b) -> 'b t
map o f
map 'a option to a 'b option using ~f
val map2 : 'a t -> 'b t -> f:('a -> 'b -> 'c) -> 'c t
map2 o f
map 'a option and 'b option to a 'c option using ~f
val call : 'a -> f:('a -> unit) t -> unit
call x f
run optional function on argument
val apply : 'a -> f:('a -> 'b) t -> 'b t
apply x f
run optional function on argument and return an option
val value : 'a t -> default:'a -> 'a
value None ~default
= default
value (Some x) ~default
= x
val value_exn : 'a t -> 'a
value_exn (Some x)
= x
.
value_exn None
raises an exception.
val value_exn_message : string -> 'a t -> 'a
value_exn_message message (Some x)
= x
.
value_exn_message message None
raises exception Failure with
string message
.
val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
val some : 'a -> 'a t
val both : 'a option -> 'b option -> ('a * 'b) option
val wrap_exn : ('a -> 'b) -> 'a -> 'b t
wrap_exn f
provides an exception-free interface to f
. It
returns a function that returns Some x
whenever f
would have
returned x
and None
whenever f
would have raised an exception.