module Option: BatOption
type'a
t ='a option
val some : 'a -> 'a option
some x
returns Some x
.
val may : ('a -> unit) -> 'a option -> unit
may f (Some x)
calls f x
and may f None
does nothing.
val map : ('a -> 'b) -> 'a option -> 'b option
map f (Some x)
returns Some (f x)
and map f None
returns None
.
val bind : 'a option -> ('a -> 'b option) -> 'b option
bind (Some x) f
returns f x
and bind None f
returns None
.
val apply : ('a -> 'a) option -> 'a -> 'a
apply None x
returns x
and apply (Some f) x
returns f x
val filter : ('a -> bool) -> 'a option -> 'a option
filter f None
returns None
, filter f (Some x)
returns Some x
if f x
is true, and None
otherwise.
val default : 'a -> 'a option -> 'a
default x (Some v)
returns v
and default x None
returns x
.
val (|?) : 'a option -> 'a -> 'a
Like BatOption.default
, with the arguments reversed.
None |? 10
returns 10
, while Some "foo" |? "bar"
returns "foo"
.
Note This operator does not short circuit like ( || )
and ( && )
.
Both arguments will be evaluated.
val default_delayed : (unit -> 'a) -> 'a option -> 'a
Like BatOption.default
, but the default value is passed as a thunk that
is only computed if needed.
val map_default : ('a -> 'b) -> 'b -> 'a option -> 'b
map_default f x (Some v)
returns f v
and map_default f x None
returns x
.
val map_default_delayed : ('a -> 'b) -> (unit -> 'b) -> 'a option -> 'b
Like BatOption.map_default
, but the default value is passed as a thunk that
is only computed if needed.
val is_none : 'a option -> bool
is_none None
returns true
otherwise it returns false
.
val is_some : 'a option -> bool
is_some (Some x)
returns true
otherwise it returns false
.
val get : 'a option -> 'a
get (Some x)
returns x
.
Invalid_argument
on get None
.val get_exn : 'a option -> exn -> 'a
get_exn (Some x) e
returns x
and get_exn None e
raises e
.
val compare : ?cmp:('a -> 'a -> int) -> 'a option -> 'a option -> int
Compare two options, possibly using custom comparators for the
value. None
is always assumed to be less than Some _
. The
parameter cmp
defaults to Pervasives.compare
.
val eq : ?eq:('a -> 'a -> bool) -> 'a option -> 'a option -> bool
Test for equality between option types, possibly using a custom
equality predicate. The parameter eq
defaults to
Pervasives.(=)
.
val enum : 'a option -> 'a BatEnum.t
enum (Some x)
returns the singleton x
, while enum None
returns
the empty enumeration.
val of_enum : 'a BatEnum.t -> 'a option
of_enum e
consumes the first element of e
, if it exists, and
returns Some e
. If e
is empty, return None
.
module Monad:sig
..end
This module provides everything needed to write and execute computations in the Option monad.
val ord : 'a BatOrd.ord -> 'a option BatOrd.ord
Comparison between optional values
val print : ('a BatInnerIO.output -> 'b -> unit) ->
'a BatInnerIO.output -> 'b t -> unit
module Labels:sig
..end
Operations on options, with labels.
module Infix:sig
..end