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Module Stream = Async_kernel.Async_stream

Signature

type 'a t = 'a Async_kernel.Tail.Stream.t

sexp_of_t t f returns a sexp of all of the elements currently available in the stream. It is just for display purposes. There is no t_of_sexp.

val sexp_of_t : ('a -> Sexplib.Sexp.t) -> 'a t -> Sexplib.Sexp.t
val create : ('a Async_kernel.Tail.t -> unit) -> 'a t

create f returns a stream t and calls f tail, where the elements of the stream are determined as the tail is extended, and the end of the stream is reached when the tail is closed.

type 'a next =
| Nil
| Cons of 'a * 'a t

next t returns a deferred that will become determined when the next part of the stream is determined. This is Cons (v, t'), where v is the next element of the stream and t' is the rest of the stream, or with Nil at the end of the stream.

val next : 'a t -> 'a next Deferred.t
val first_exn : 'a t -> 'a Deferred.t

first_exn t returns a deferred that becomes determined with the first element of t.

Streams can be converted to and from lists. Although, conversion to a list returns a deferred, because the stream is determined asynchronously.

val of_list : 'a list -> 'a t

of_list l returns a stream with the elements of list l.

val to_list : 'a t -> 'a list Deferred.t

to_list t returns a deferred that will become determined with the list of elements in t, if the end of t is reached.

val of_fun : (unit -> 'a Deferred.t) -> 'a t

of_fun f returns a stream whose elements are determined by calling f forever.

val copy_to_tail : 'a t -> 'a Async_kernel.Tail.t -> unit Deferred.t

copy_to_tail t tail reads elements from t and puts them in tail, until the end of t is reached.

Sequence operations ---------------------------------------------------------------------- There are the usual sequence operations:

      append, fold, iter, map, filter_map, take

There are also deferred variants:

      iter', map', filter_map'

These take anonymous functions that return deferreds generalizing the usual sequence operation and allowing the client to control the rate at which the sequence is processed.

val append : 'a t -> 'a t -> 'a t

append t1 t2 returns a stream with all the values of t1, in order, and if t1 ends, these values are followed by all the values of t2.

val concat : 'a t t -> 'a t

concat t takes a stream of streams and produces a stream that is the concatenation of each stream in order (you see all of stream 1, then all of stream 2... etc.)

val available_now : 'a t -> 'a list * 'a t

available_now t returns t prefix of t that is available now, along with the rest of the stream.

val filter_deprecated : 'a t -> f:('a -> bool) -> 'a t

filter_deprecated s ~f returns a stream with one element, v, for each v in s such with f v = true.

Using filter_deprecated can easily lead to space leaks. It is better to use Async.Pipe than Async.Stream.

val filter_map_deprecated : 'a t -> f:('a -> 'b option) -> 'b t

filter_map_deprecated s ~f returns a stream with one element, v', for each v in s such with f v = Some v'.

Using filter_map_deprecated can easily lead to space leaks. It is better to use Async.Pipe than Async.Stream.

val fold' : 'a t -> init:'b -> f:('b -> 'a -> 'b Deferred.t) -> 'b Deferred.t

fold' t ~init ~f is like list fold, walking over the elements of the stream in order, as they become available. fold' returns a deferred that will yield the final value of the accumulator, if the end of the stream is reached.

val fold : 'a t -> init:'b -> f:('b -> 'a -> 'b) -> 'b Deferred.t

fold t ~init ~f is a variant of fold' in which f does not return a deferred.

val iter' : 'a t -> f:('a -> unit Deferred.t) -> unit Deferred.t

iter' t ~f applies f to each element of the stream in turn, as they become available. It continues onto the next element only after the deferred returned by f becomes determined.

val closed : _ t -> unit Deferred.t

closed t returns a deferred that becomes determined when the end of t is reached.

val iter : 'a t -> f:('a -> unit) -> unit

iter t ~f = don't_wait_for (iter' t ~f:(fun a -> f a; Deferred.unit))

val take_until : 'a t -> unit Deferred.t -> 'a t

take_until t d returns a stream t' that has the same elements as t up until d becomes determined.

val iter_durably' : 'a t -> f:('a -> unit Deferred.t) -> unit Deferred.t

iter_durably' t ~f is like iter' t ~f, except if f raises an exception it continues with the next element of the stream *and* reraises the exception (to the monitor in scope when iter_durably was called).

iter_durably t ~f is like iter t ~f, except if f raises an exception it continues with the next element of the stream *and* reraises the exception (to the monitor in scope when iter_durably was called).

iter_durably_report_end t ~f is equivalent to iter_durably' t ~f:(fun x -> return (f x)) but it is more efficient

val iter_durably : 'a t -> f:('a -> unit) -> unit
val iter_durably_report_end : 'a t -> f:('a -> unit) -> unit Deferred.t
val length : 'a t -> int Deferred.t

length s returns a deferred that is determined when the end of s is reached, taking the value of the number of elements in s

val map' : 'a t -> f:('a -> 'b Deferred.t) -> 'b t

map' t f creates a new stream that with one element, (f v), for each element v of t.

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

map t ~f creates a new stream that with one element, (f v), for each element v of t. map t f = map' t ~f:(fun a -> return (f a)).

val first_n : 'a t -> int -> 'a t

first_n t n returns a stream with the first n elements of t, if t has n or more elements, or it returns t.

Stream generation ----------------------------------------------------------------------

val unfold : 'b -> f:('b -> ('a * 'b) option Deferred.t) -> 'a t

unfold b f returns a stream a1; a2; ...; an whose elements are determined by the equations: 

      b0 = b
      Some (a1, b1) = f b0
      Some (a2, b2) = f b1
      ...
      None = f bn

Miscellaneous operations ----------------------------------------------------------------------

val split : ?stop:unit Deferred.t -> ?f:('a -> [
| `Continue
| `Found of 'b
]) -> 'a t -> 'a t * [
| `End_of_stream
| `Stopped of 'a t
| `Found of 'b * 'a t
] Deferred.t

split ~stop ~f t returns a pair (p, d), where p is a prefix of t that ends for one of three reasons: 

      1. [t] ends
      2. stop becomes determined
      3. f returns `Found

The deferred d describes why the prefix ended, and returns the suffix of the stream in case (2) or (3).

val find : 'a t -> f:('a -> bool) -> [
| `End_of_stream
| `Found of 'a * 'a t
] Deferred.t

find ~f t returns a deferred that becomes determined when f x is true for some element of t, or if the end of the stream is reached

val ungroup : 'a list t -> 'a t

ungroup t takes a stream of lists and unpacks the items from each list into a single stream

val interleave : 'a t t -> 'a t

interleave list takes a stream of streams and returns a stream of their items interleaved as they become determined. The interleaved stream will be closed when the outer stream and all of the inner streams have been closed.