Module Base.Option

Option type.

type 'a t = 'a option
include sig ... end
val compare : ('a ‑> 'a ‑> int) ‑> 'a t ‑> 'a t ‑> int
val hash_fold_t : (Hash.state ‑> 'a ‑> Hash.state) ‑> Hash.state ‑> 'a t ‑> Hash.state
val t_of_sexp : (Sexp.t ‑> 'a) ‑> Sexp.t ‑> 'a t
val sexp_of_t : ('a ‑> Sexp.t) ‑> 'a t ‑> Sexp.t
include Container.S1 with type a t := a t
type 'a t
val mem : 'a t ‑> 'a ‑> equal:('a ‑> 'a ‑> bool) ‑> bool

Checks whether the provided element is there, using equal.

val length : 'a t ‑> int
val is_empty : 'a t ‑> bool
val iter : 'a t ‑> f:('a ‑> unit) ‑> unit
val fold : 'a t ‑> init:'accum ‑> f:('accum ‑> 'a ‑> 'accum) ‑> 'accum

fold t ~init ~f returns f (... f (f (f init e1) e2) e3 ...) en, where e1..en are the elements of t

val fold_result : 'a t ‑> init:'accum ‑> f:('accum ‑> 'a ‑> ('accum, 'e) Result.t) ‑> ('accum, 'e) Result.t

fold_result t ~init ~f is a short-circuiting version of fold that runs in the Result monad. If f returns an Error _, that value is returned without any additional invocations of f.

val fold_until : 'a t ‑> init:'accum ‑> f:('accum ‑> 'a ‑> ('accum, 'final) Base__.Container_intf.Continue_or_stop.t) ‑> finish:('accum ‑> 'final) ‑> 'final

fold_until t ~init ~f ~finish is a short-circuiting version of fold. If f returns Stop _ the computation ceases and results in that value. If f returns Continue _, the fold will proceed. If f never returns Stop _, the final result is computed by finish.

val exists : 'a t ‑> f:('a ‑> bool) ‑> bool

Returns true if and only if there exists an element for which the provided function evaluates to true. This is a short-circuiting operation.

val for_all : 'a t ‑> f:('a ‑> bool) ‑> bool

Returns true if and only if the provided function evaluates to true for all elements. This is a short-circuiting operation.

val count : 'a t ‑> f:('a ‑> bool) ‑> int

Returns the number of elements for which the provided function evaluates to true.

val sum : (module Commutative_group.S with type t = 'sum) ‑> 'a t ‑> f:('a ‑> 'sum) ‑> 'sum

Returns the sum of f i for all i in the container.

val find : 'a t ‑> f:('a ‑> bool) ‑> 'a option

Returns as an option the first element for which f evaluates to true.

val find_map : 'a t ‑> f:('a ‑> 'b option) ‑> 'b option

Returns the first evaluation of f that returns Some, and returns None if there is no such element.

val to_list : 'a t ‑> 'a list
val to_array : 'a t ‑> 'a array
val min_elt : 'a t ‑> compare:('a ‑> 'a ‑> int) ‑> 'a option

Returns a minimum (resp maximum) element from the collection using the provided compare function, or None if the collection is empty. In case of a tie, the first element encountered while traversing the collection is returned. The implementation uses fold so it has the same complexity as fold.

val max_elt : 'a t ‑> compare:('a ‑> 'a ‑> int) ‑> 'a option
include Equal.S1 with type a t := a t
type 'a t
val equal : 'a Equal.equal ‑> 'a t Equal.equal
include Invariant.S1 with type a t := a t
type 'a t

Options form a monad, where return x = Some x, (None >>= f) = None, and (Some x >>= f) = f x.

include Monad.S with type a t := a t
type 'a t
include Base__.Monad_intf.S_without_syntax with type a t := a t
type 'a t
include Base__.Monad_intf.Infix with type a t := a t
type 'a t
val (>>=) : 'a t ‑> ('a ‑> 'b t) ‑> 'b t

t >>= f returns a computation that sequences the computations represented by two monad elements. The resulting computation first does t to yield a value v, and then runs the computation returned by f v.

val (>>|) : 'a t ‑> ('a ‑> 'b) ‑> 'b t

t >>| f is t >>= (fun a -> return (f a)).

module Monad_infix : Base__.Monad_intf.Infix with type a t := a t
val bind : 'a t ‑> f:('a ‑> 'b t) ‑> 'b t

bind t ~f = t >>= f

val return : 'a ‑> 'a t

return v returns the (trivial) computation that returns v.

val map : 'a t ‑> f:('a ‑> 'b) ‑> 'b t

map t ~f is t >>| f.

val join : 'a t t ‑> 'a t

join t is t >>= (fun t' -> t').

val ignore_m : 'a t ‑> unit t

ignore_m t is map t ~f:(fun _ -> ()). ignore_m used to be called ignore, but we decided that was a bad name, because it shadowed the widely used Pervasives.ignore. Some monads still do let ignore = ignore_m for historical reasons.

val all : 'a t list ‑> 'a list t
val all_unit : unit t list ‑> unit t
val all_ignore : unit t list ‑> unit t
  • Deprecated [since 2018-02] Use [all_unit]
include Base__.Monad_intf.Syntax with type a t := a t
type 'a t
module Let_syntax : sig ... end
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 ~default ~f is the same as function Some x -> f x | None -> default.

val map2 : 'a t ‑> 'b t ‑> f:('a ‑> 'b ‑> 'c) ‑> 'c t

map2 o f maps 'a option and 'b option to a 'c option using ~f.

val call : 'a ‑> f:('a ‑> unit) t ‑> unit

call x f runs an optional function ~f on the argument.

val value : 'a t ‑> default:'a ‑> 'a

value None ~default = defaultvalue (Some x) ~default = x

val value_exn : ?⁠here:Base__.Source_code_position0.t ‑> ?⁠error:Error.t ‑> ?⁠message:string ‑> 'a t ‑> 'a

value_exn (Some x) = x. value_exn None raises an error whose contents contain the supplied ~here, ~error, and message, or a default message if none are supplied.

val some : 'a ‑> 'a t
val both : 'a t ‑> 'b t ‑> ('a * 'b) t
val first_some : 'a t ‑> 'a t ‑> 'a t
val some_if : bool ‑> 'a ‑> 'a t
val merge : 'a t ‑> 'a t ‑> f:('a ‑> 'a ‑> 'a) ‑> 'a t

merge a b ~f merges together the values from a and b using f. If both a and b are None, returns None. If only one is Some, returns that one, and if both are Some, returns Some of the result of applying f to the contents of a and b.

val filter : 'a t ‑> f:('a ‑> bool) ‑> 'a t
val try_with : (unit ‑> 'a) ‑> 'a t

try_with f returns Some x if f returns x and None if f raises an exception. See Result.try_with if you'd like to know which exception.

val validate : none:unit Validate.check ‑> some:'a Validate.check ‑> 'a t Validate.check