Computer Science Experimentation

Friday, August 10, 2012

HTML5 Web Workers- Agent based computantion for the Web Browser


This post presents an example using HTML5 Web Workers.

The Web Workers are very similar to the Agent based computation presented in previous posts:

·        Agent based example using F# MailboxProcessor


·        Real-time Computation Engine with F#


Example:


This example use one HTML5 main page and one Web Worker.

The example consists of two parts:

1.      Non-state-based request/reply messages to the Web Worker:

Sum: send a message with two values and receive back the sum of them

2.      State-based interaction with the Web Worker:

Check State: receives from the Web Worker its state (idle, active)

Go to Active: starts in the Web Worker a periodic procedure every 15 sec that generate two random numbers and keeps an accumulation of them

Clear Accumulation

Go to Idle: stops the periodic procedure in the Web Worker 

Check the full article at:
https://skydrive.live.com/?cid=BDC87EF39B001785&id=BDC87EF39B001785%21110#!/view.aspx?cid=BDC87EF39B001785&resid=BDC87EF39B001785%21730



Chat Application using Web Sockets Self-Hosted Server with F#

This post presents an Chat application in F# using the library:

The Chat application is based on Paul Batum example at:
The server is self-hosted.
I tried to make the application to be hosted in F# interactive console by making the configuration programmatically without success. Because of that, the F# application is compiled in order to use the App.cfg .

Using System.Json in F#


The System.Json library is only available for Silverligh environment.

A beta version for .NET can be obtained from Nuget (http://nuget.org/packages/System.Json).

This is the documentation at MSDN:
(http://msdn.microsoft.com/en-us/library/system.json(v=vs.95).aspx)

The System.Json namespace provides standards-based support for the serialization of JavaScript Object Notation (JSON).

JSON is a lightweight, text-based data interchange format that is used to serialize structured data for transmission over networks. It has three primitive data types: string, number, and Boolean. It has two data structures: array and object. An array is an ordered collection of values, where the value can be a JSON primitive, object or array. An object is an unordered set of key/value pairs. The key is a string and the value, as with the array, can be a JSON primitive, object, or array.

In this documentation, the serialized textual representation of JSON is referred to as “text-based JSON” to distinguish it from the deserialized representation of JSON as a Common Language Runtime (CLR) type, which is referred to here as a “JSON CLR type” or as a “JSON CLR object” if we are referring to an instance of the type.

JSON CLR types represent the three text-based JSON primitives with the JsonPrimitive type. The JsonType() property indicates which primitive is contained in the type instance: String, Number, or Boolean.

JSON CLR types represent the two text-based structured types with JsonArray and JsonObject. A JsonArray is an ordered sequence of zero or more JsonValue objects. A JsonValue is the JSON CLR representation of a JSON text-based value, which can be either a primitive or structured type. A JsonObject is an unordered collection of zero or more String/JsonValue pairs, which represent the key/value pairs of the text-based JSON object.

F# Example:

//Using System.Json.dll
//By Celso Axelrud on 8/10/2012

open System
open System.Collections.Generic

#r @"C:\Users\caxelrud\Documents\Visual Studio 2012\Projects\WebSck_Host_2\packages\System.Json.4.0.20126.16343\lib\net40\System.Json.dll"
open System.Json

let j="[{\"a\":\"foo\",\"b\":\"bar\"},{\"a\":\"another foo\",\"b\":\"another bar\",\"c\":100}]"
let jsonObj = JsonValue.Parse(j)

jsonObj.Count;;
(*> val it : int = 2 *)

jsonObj.[0].["a"].ReadAs<string>()
(*> val it : string = "foo" *)

jsonObj.[1].["c"].ReadAs<int>();;
(*> val it : int = 100 *)

//New Json object
let jsonNew = new JsonObject(new KeyValuePair<string,JsonValue>("mainValue", JsonPrimitive(12345)))

jsonNew.ToString()
(*> val it : string = "{"mainValue":12345}" *)


Saturday, August 4, 2012

Web Socket Self-Hosted Servers with WCF and F#

This post presents an Echo application using different libraries:
System.Net.Websockets (.NET 4.5)
Microsoft.ServiceModel.Websockets (beta)