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Async demo

Async demo...

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open System
open System.IO
open System.Net
open System.Threading

// ------------------------------------------------------------------
// Read a stream into the memory and then return it as a string
// ------------------------------------------------------------------

let readToEnd (stream:Stream) = async {
  // Allocate 1kb buffer for downloading dat
  let buffer = Array.zeroCreate 1024
  use output = new MemoryStream()
  let finished = ref false
  
  while not finished.Value do
    // Download one (at most) 1kb chunk and copy it
    let! count = stream.AsyncRead(buffer, 0, 1024)
    do! output.AsyncWrite(buffer, 0, count)
    finished := count <= 0

  // Read all data into a string
  output.Seek(0L, SeekOrigin.Begin) |> ignore
  use sr = new StreamReader(output)
  return sr.ReadToEnd() }


// ------------------------------------------------------------------
// Download a web page using HttpWebRequest
// ------------------------------------------------------------------

/// Downlaod content of a web site using 'readToEnd'
let download url = async {
  let request = HttpWebRequest.Create(Uri(url))
  use! response = request.AsyncGetResponse()
  use stream = response.GetResponseStream()
  let! res = readToEnd stream 
  return res }

// Create a list of sites to download 

let sites = 
  [ "http://webstep.no"
    "http://microsoft.com"
    "http://bing.com"
    "http://google.com" ]

// Fork-join parallelism (download all)
let downloads = sites |> List.map download
let alldata = Async.Parallel downloads

// Run synchronously & block the thread
let res = Async.RunSynchronously(alldata)

// Create a background task that will eventually
// print (or do some other side-effect)
let work = async { 
  let! res = alldata 
  for it in res do
    printfn "%d" it.Length }

Async.Start(work)
namespace System
namespace System.IO
namespace System.Net
namespace System.Threading
val readToEnd : stream:Stream -> Async<string>

Full name: Script.readToEnd
val stream : Stream
type Stream =
  inherit MarshalByRefObject
  member BeginRead : buffer:byte[] * offset:int * count:int * callback:AsyncCallback * state:obj -> IAsyncResult
  member BeginWrite : buffer:byte[] * offset:int * count:int * callback:AsyncCallback * state:obj -> IAsyncResult
  member CanRead : bool
  member CanSeek : bool
  member CanTimeout : bool
  member CanWrite : bool
  member Close : unit -> unit
  member CopyTo : destination:Stream -> unit + 1 overload
  member Dispose : unit -> unit
  member EndRead : asyncResult:IAsyncResult -> int
  ...

Full name: System.IO.Stream
val async : AsyncBuilder

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.async
val buffer : byte []
type Array =
  member Clone : unit -> obj
  member CopyTo : array:Array * index:int -> unit + 1 overload
  member GetEnumerator : unit -> IEnumerator
  member GetLength : dimension:int -> int
  member GetLongLength : dimension:int -> int64
  member GetLowerBound : dimension:int -> int
  member GetUpperBound : dimension:int -> int
  member GetValue : [<ParamArray>] indices:int[] -> obj + 7 overloads
  member Initialize : unit -> unit
  member IsFixedSize : bool
  ...

Full name: System.Array
val zeroCreate : count:int -> 'T []

Full name: Microsoft.FSharp.Collections.Array.zeroCreate
val output : MemoryStream
Multiple items
type MemoryStream =
  inherit Stream
  new : unit -> MemoryStream + 6 overloads
  member CanRead : bool
  member CanSeek : bool
  member CanWrite : bool
  member Capacity : int with get, set
  member Flush : unit -> unit
  member GetBuffer : unit -> byte[]
  member Length : int64
  member Position : int64 with get, set
  member Read : buffer:byte[] * offset:int * count:int -> int
  ...

Full name: System.IO.MemoryStream

--------------------
MemoryStream() : unit
MemoryStream(capacity: int) : unit
MemoryStream(buffer: byte []) : unit
MemoryStream(buffer: byte [], writable: bool) : unit
MemoryStream(buffer: byte [], index: int, count: int) : unit
MemoryStream(buffer: byte [], index: int, count: int, writable: bool) : unit
MemoryStream(buffer: byte [], index: int, count: int, writable: bool, publiclyVisible: bool) : unit
val finished : bool ref
Multiple items
val ref : value:'T -> 'T ref

Full name: Microsoft.FSharp.Core.Operators.ref

--------------------
type 'T ref = Ref<'T>

Full name: Microsoft.FSharp.Core.ref<_>
val not : value:bool -> bool

Full name: Microsoft.FSharp.Core.Operators.not
property Ref.Value: bool
val count : int
member Stream.AsyncRead : count:int -> Async<byte []>
member Stream.AsyncRead : buffer:byte [] * ?offset:int * ?count:int -> Async<int>
member Stream.AsyncWrite : buffer:byte [] * ?offset:int * ?count:int -> Async<unit>
MemoryStream.Seek(offset: int64, loc: SeekOrigin) : int64
type SeekOrigin =
  | Begin = 0
  | Current = 1
  | End = 2

Full name: System.IO.SeekOrigin
field SeekOrigin.Begin = 0
val ignore : value:'T -> unit

Full name: Microsoft.FSharp.Core.Operators.ignore
val sr : StreamReader
Multiple items
type StreamReader =
  inherit TextReader
  new : stream:Stream -> StreamReader + 9 overloads
  member BaseStream : Stream
  member Close : unit -> unit
  member CurrentEncoding : Encoding
  member DiscardBufferedData : unit -> unit
  member EndOfStream : bool
  member Peek : unit -> int
  member Read : unit -> int + 1 overload
  member ReadLine : unit -> string
  member ReadToEnd : unit -> string
  ...

Full name: System.IO.StreamReader

--------------------
StreamReader(stream: Stream) : unit
StreamReader(path: string) : unit
StreamReader(stream: Stream, detectEncodingFromByteOrderMarks: bool) : unit
StreamReader(stream: Stream, encoding: Text.Encoding) : unit
StreamReader(path: string, detectEncodingFromByteOrderMarks: bool) : unit
StreamReader(path: string, encoding: Text.Encoding) : unit
StreamReader(stream: Stream, encoding: Text.Encoding, detectEncodingFromByteOrderMarks: bool) : unit
StreamReader(path: string, encoding: Text.Encoding, detectEncodingFromByteOrderMarks: bool) : unit
StreamReader(stream: Stream, encoding: Text.Encoding, detectEncodingFromByteOrderMarks: bool, bufferSize: int) : unit
StreamReader(path: string, encoding: Text.Encoding, detectEncodingFromByteOrderMarks: bool, bufferSize: int) : unit
StreamReader.ReadToEnd() : string
val download : url:string -> Async<string>

Full name: Script.download


 Downlaod content of a web site using 'readToEnd'
val url : string
val request : WebRequest
type HttpWebRequest =
  inherit WebRequest
  member Abort : unit -> unit
  member Accept : string with get, set
  member AddRange : range:int -> unit + 7 overloads
  member Address : Uri
  member AllowAutoRedirect : bool with get, set
  member AllowWriteStreamBuffering : bool with get, set
  member AutomaticDecompression : DecompressionMethods with get, set
  member BeginGetRequestStream : callback:AsyncCallback * state:obj -> IAsyncResult
  member BeginGetResponse : callback:AsyncCallback * state:obj -> IAsyncResult
  member ClientCertificates : X509CertificateCollection with get, set
  ...

Full name: System.Net.HttpWebRequest
WebRequest.Create(requestUri: Uri) : WebRequest
WebRequest.Create(requestUriString: string) : WebRequest
Multiple items
type Uri =
  new : uriString:string -> Uri + 5 overloads
  member AbsolutePath : string
  member AbsoluteUri : string
  member Authority : string
  member DnsSafeHost : string
  member Equals : comparand:obj -> bool
  member Fragment : string
  member GetComponents : components:UriComponents * format:UriFormat -> string
  member GetHashCode : unit -> int
  member GetLeftPart : part:UriPartial -> string
  ...

Full name: System.Uri

--------------------
Uri(uriString: string) : unit
Uri(uriString: string, uriKind: UriKind) : unit
Uri(baseUri: Uri, relativeUri: string) : unit
Uri(baseUri: Uri, relativeUri: Uri) : unit
val response : WebResponse
member WebRequest.AsyncGetResponse : unit -> Async<WebResponse>
WebResponse.GetResponseStream() : Stream
val res : string
val sites : string list

Full name: Script.sites
val downloads : Async<string> list

Full name: Script.downloads
Multiple items
module List

from Microsoft.FSharp.Collections

--------------------
type List<'T> =
  | ( [] )
  | ( :: ) of Head: 'T * Tail: 'T list
  interface IEnumerable
  interface IEnumerable<'T>
  member Head : 'T
  member IsEmpty : bool
  member Item : index:int -> 'T with get
  member Length : int
  member Tail : 'T list
  static member Cons : head:'T * tail:'T list -> 'T list
  static member Empty : 'T list

Full name: Microsoft.FSharp.Collections.List<_>
val map : mapping:('T -> 'U) -> list:'T list -> 'U list

Full name: Microsoft.FSharp.Collections.List.map
val alldata : Async<string []>

Full name: Script.alldata
Multiple items
type Async
static member AsBeginEnd : computation:('Arg -> Async<'T>) -> ('Arg * AsyncCallback * obj -> IAsyncResult) * (IAsyncResult -> 'T) * (IAsyncResult -> unit)
static member AwaitEvent : event:IEvent<'Del,'T> * ?cancelAction:(unit -> unit) -> Async<'T> (requires delegate and 'Del :> Delegate)
static member AwaitIAsyncResult : iar:IAsyncResult * ?millisecondsTimeout:int -> Async<bool>
static member AwaitTask : task:Task<'T> -> Async<'T>
static member AwaitWaitHandle : waitHandle:WaitHandle * ?millisecondsTimeout:int -> Async<bool>
static member CancelDefaultToken : unit -> unit
static member Catch : computation:Async<'T> -> Async<Choice<'T,exn>>
static member FromBeginEnd : beginAction:(AsyncCallback * obj -> IAsyncResult) * endAction:(IAsyncResult -> 'T) * ?cancelAction:(unit -> unit) -> Async<'T>
static member FromBeginEnd : arg:'Arg1 * beginAction:('Arg1 * AsyncCallback * obj -> IAsyncResult) * endAction:(IAsyncResult -> 'T) * ?cancelAction:(unit -> unit) -> Async<'T>
static member FromBeginEnd : arg1:'Arg1 * arg2:'Arg2 * beginAction:('Arg1 * 'Arg2 * AsyncCallback * obj -> IAsyncResult) * endAction:(IAsyncResult -> 'T) * ?cancelAction:(unit -> unit) -> Async<'T>
static member FromBeginEnd : arg1:'Arg1 * arg2:'Arg2 * arg3:'Arg3 * beginAction:('Arg1 * 'Arg2 * 'Arg3 * AsyncCallback * obj -> IAsyncResult) * endAction:(IAsyncResult -> 'T) * ?cancelAction:(unit -> unit) -> Async<'T>
static member FromContinuations : callback:(('T -> unit) * (exn -> unit) * (OperationCanceledException -> unit) -> unit) -> Async<'T>
static member Ignore : computation:Async<'T> -> Async<unit>
static member OnCancel : interruption:(unit -> unit) -> Async<IDisposable>
static member Parallel : computations:seq<Async<'T>> -> Async<'T []>
static member RunSynchronously : computation:Async<'T> * ?timeout:int * ?cancellationToken:CancellationToken -> 'T
static member Sleep : millisecondsDueTime:int -> Async<unit>
static member Start : computation:Async<unit> * ?cancellationToken:CancellationToken -> unit
static member StartAsTask : computation:Async<'T> * ?taskCreationOptions:TaskCreationOptions * ?cancellationToken:CancellationToken -> Task<'T>
static member StartChild : computation:Async<'T> * ?millisecondsTimeout:int -> Async<Async<'T>>
static member StartChildAsTask : computation:Async<'T> * ?taskCreationOptions:TaskCreationOptions -> Async<Task<'T>>
static member StartImmediate : computation:Async<unit> * ?cancellationToken:CancellationToken -> unit
static member StartWithContinuations : computation:Async<'T> * continuation:('T -> unit) * exceptionContinuation:(exn -> unit) * cancellationContinuation:(OperationCanceledException -> unit) * ?cancellationToken:CancellationToken -> unit
static member SwitchToContext : syncContext:SynchronizationContext -> Async<unit>
static member SwitchToNewThread : unit -> Async<unit>
static member SwitchToThreadPool : unit -> Async<unit>
static member TryCancelled : computation:Async<'T> * compensation:(OperationCanceledException -> unit) -> Async<'T>
static member CancellationToken : Async<CancellationToken>
static member DefaultCancellationToken : CancellationToken

Full name: Microsoft.FSharp.Control.Async

--------------------
type Async<'T>

Full name: Microsoft.FSharp.Control.Async<_>
static member Async.Parallel : computations:seq<Async<'T>> -> Async<'T []>
val res : string []

Full name: Script.res
static member Async.RunSynchronously : computation:Async<'T> * ?timeout:int * ?cancellationToken:CancellationToken -> 'T
val work : Async<unit>

Full name: Script.work
val res : string []
val it : string
val printfn : format:Printf.TextWriterFormat<'T> -> 'T

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.printfn
property String.Length: int
static member Async.Start : computation:Async<unit> * ?cancellationToken:CancellationToken -> unit
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More information

Link:http://fssnip.net/nP
Posted:3 years ago
Author:Tomas Petricek
Tags: async