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  • Are closures with side-effects considered "functional style"?

    - by Giorgio
    Many modern programming languages support some concept of closure, i.e. of a piece of code (a block or a function) that Can be treated as a value, and therefore stored in a variable, passed around to different parts of the code, be defined in one part of a program and invoked in a totally different part of the same program. Can capture variables from the context in which it is defined, and access them when it is later invoked (possibly in a totally different context). Here is an example of a closure written in Scala: def filterList(xs: List[Int], lowerBound: Int): List[Int] = xs.filter(x => x >= lowerBound) The function literal x => x >= lowerBound contains the free variable lowerBound, which is closed (bound) by the argument of the function filterList that has the same name. The closure is passed to the library method filter, which can invoke it repeatedly as a normal function. I have been reading a lot of questions and answers on this site and, as far as I understand, the term closure is often automatically associated with functional programming and functional programming style. The definition of function programming on wikipedia reads: In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state. and further on [...] in functional code, the output value of a function depends only on the arguments that are input to the function [...]. Eliminating side effects can make it much easier to understand and predict the behavior of a program, which is one of the key motivations for the development of functional programming. On the other hand, many closure constructs provided by programming languages allow a closure to capture non-local variables and change them when the closure is invoked, thus producing a side effect on the environment in which they were defined. In this case, closures implement the first idea of functional programming (functions are first-class entities that can be moved around like other values) but neglect the second idea (avoiding side-effects). Is this use of closures with side effects considered functional style or are closures considered a more general construct that can be used both for a functional and a non-functional programming style? Is there any literature on this topic? IMPORTANT NOTE I am not questioning the usefulness of side-effects or of having closures with side effects. Also, I am not interested in a discussion about the advantages / disadvantages of closures with or without side effects. I am only interested to know if using such closures is still considered functional style by the proponent of functional programming or if, on the contrary, their use is discouraged when using a functional style.

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  • OpenSource Flow Charting

    - by lazyPower
    I'm looking for an application that drops output in a portable format, maybe export as an image file so I can flowchart some application designs and submit them to my boss for professional review. From what I've seen dia is about the de-facto standard for linux flowcharting, but maybe some of you out there in askubuntu land have some other suggestions for me to examine. Please keep in mind it has to offer a professional / attractive look on the final product. Maybe some color coordination of the options (logic structures are all purple, input statements are orange... for example)

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  • Ping one remote server from another remote server

    - by user666254
    It's simple to ping a server in C#, but suppose I have servers A, B and C. A connects to B. A asks B to ping C, to check that B can talk to C. A needs to read the outcome. Now, first of all is this possible without installing an application onto B? In other words, can I perform the entire check from just running a program on A? If so, can anyone suggest the route I would take to achieve this? I've looked at sockets but from the examples I've seen these require a client AND server application to function.

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  • Collaborative Whiteboard using WebSocket in GlassFish 4 - Text/JSON and Binary/ArrayBuffer Data Transfer (TOTD #189)

    - by arungupta
    This blog has published a few blogs on using JSR 356 Reference Implementation (Tyrus) as its integrated in GlassFish 4 promoted builds. TOTD #183: Getting Started with WebSocket in GlassFish TOTD #184: Logging WebSocket Frames using Chrome Developer Tools, Net-internals and Wireshark TOTD #185: Processing Text and Binary (Blob, ArrayBuffer, ArrayBufferView) Payload in WebSocket TOTD #186: Custom Text and Binary Payloads using WebSocket One of the typical usecase for WebSocket is online collaborative games. This Tip Of The Day (TOTD) explains a sample that can be used to build such games easily. The application is a collaborative whiteboard where different shapes can be drawn in multiple colors. The shapes drawn on one browser are automatically drawn on all other peer browsers that are connected to the same endpoint. The shape, color, and coordinates of the image are transfered using a JSON structure. A browser may opt-out of sharing the figures. Alternatively any browser can send a snapshot of their existing whiteboard to all other browsers. Take a look at this video to understand how the application work and the underlying code. The complete sample code can be downloaded here. The code behind the application is also explained below. The web page (index.jsp) has a HTML5 Canvas as shown: <canvas id="myCanvas" width="150" height="150" style="border:1px solid #000000;"></canvas> And some radio buttons to choose the color and shape. By default, the shape, color, and coordinates of any figure drawn on the canvas are put in a JSON structure and sent as a message to the WebSocket endpoint. The JSON structure looks like: { "shape": "square", "color": "#FF0000", "coords": { "x": 31.59999942779541, "y": 49.91999053955078 }} The endpoint definition looks like: @WebSocketEndpoint(value = "websocket",encoders = {FigureDecoderEncoder.class},decoders = {FigureDecoderEncoder.class})public class Whiteboard { As you can see, the endpoint has decoder and encoder registered that decodes JSON to a Figure (a POJO class) and vice versa respectively. The decode method looks like: public Figure decode(String string) throws DecodeException { try { JSONObject jsonObject = new JSONObject(string); return new Figure(jsonObject); } catch (JSONException ex) { throw new DecodeException("Error parsing JSON", ex.getMessage(), ex.fillInStackTrace()); }} And the encode method looks like: public String encode(Figure figure) throws EncodeException { return figure.getJson().toString();} FigureDecoderEncoder implements both decoder and encoder functionality but thats purely for convenience. But the recommended design pattern is to keep them in separate classes. In certain cases, you may even need only one of them. On the client-side, the Canvas is initialized as: var canvas = document.getElementById("myCanvas");var context = canvas.getContext("2d");canvas.addEventListener("click", defineImage, false); The defineImage method constructs the JSON structure as shown above and sends it to the endpoint using websocket.send(). An instant snapshot of the canvas is sent using binary transfer with WebSocket. The WebSocket is initialized as: var wsUri = "ws://localhost:8080/whiteboard/websocket";var websocket = new WebSocket(wsUri);websocket.binaryType = "arraybuffer"; The important part is to set the binaryType property of WebSocket to arraybuffer. This ensures that any binary transfers using WebSocket are done using ArrayBuffer as the default type seem to be blob. The actual binary data transfer is done using the following: var image = context.getImageData(0, 0, canvas.width, canvas.height);var buffer = new ArrayBuffer(image.data.length);var bytes = new Uint8Array(buffer);for (var i=0; i<bytes.length; i++) { bytes[i] = image.data[i];}websocket.send(bytes); This comprehensive sample shows the following features of JSR 356 API: Annotation-driven endpoints Send/receive text and binary payload in WebSocket Encoders/decoders for custom text payload In addition, it also shows how images can be captured and drawn using HTML5 Canvas in a JSP. How could this be turned in to an online game ? Imagine drawing a Tic-tac-toe board on the canvas with two players playing and others watching. Then you can build access rights and controls within the application itself. Instead of sending a snapshot of the canvas on demand, a new peer joining the game could be automatically transferred the current state as well. Do you want to build this game ? I built a similar game a few years ago. Do somebody want to rewrite the game using WebSocket APIs ? :-) Many thanks to Jitu and Akshay for helping through the WebSocket internals! Here are some references for you: JSR 356: Java API for WebSocket - Specification (Early Draft) and Implementation (already integrated in GlassFish 4 promoted builds) Subsequent blogs will discuss the following topics (not necessary in that order) ... Error handling Interface-driven WebSocket endpoint Java client API Client and Server configuration Security Subprotocols Extensions Other topics from the API

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  • Configuring JMS and Message Queues in GlassFish - Sample Chapter

    - by arungupta
    PacktPub released Java EE 6 with GlassFish 3 Application Server a few months after the first version in GlassFish 3 train was released. This book is a practical guide to install and configure the GlassFish 3 Application Server and develop and deploy Java EE 6 applications on this server. Recently they released a sample chapter on how to configure JMS and message queues in GlassFish. The chapter provide complete snapshots from the web-based admin console and working sample code. The Table of Contents shows that all major Java EE 6 APIs and the details of the GlassFish 3 server are covered followed by examples of its use. This book is a practical guide with a very user-friendly approach. Read about other books on Java EE and GlassFish here.

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  • Help file formats - MSHA files v CHM files

    - by TATWORTH
    Recently I was tasked with producing a help file from a C#/WPF/Crystal Reports application using Sandcastle. I have previously blogged about the problems in doing that and the change that is going into the next version of Sandcastle that allows the vagaries of Crystal (this missing BusinessObjects.Licensing.KeycodeDecoder) to be handled. At http://social.msdn.microsoft.com/Forums/en-US/devdocs/thread/0b110502-f5bb-4c56-96a5-4347a2a7a68a/, I describe how I tried each of the formats. Two of the formats could not be built and the error messages were not exactly helpful as to the cause. These two formats turned out to be obsolete. The MSHA format worked but was not suitable for a standalone application, so that left me with the older CHM format. I therefore asked on that thread "will the HTML Help 1 (CHM) format continue to be supported for the foreseeable future?".Rob Chandler, MVP in help systems, gave a very helpful answer, to the effect that there is not yet a replacement for the CHM format.

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  • Designing call center applications, what to consider.

    - by Espen Schulstad
    We have customers calling in to place orders. What sort of considerations should I make when building a call center application. Speed is a factor here. We had a powerbuilder application that was extremly fast for a trained user. We want to have the same sort of speed in our new production system. So some thoughts I've made are: Hotkeys are important. Is it faster to use a "wizard", step by step, or should I try to place everything important about the order logically on one sceen and have another screen where you do all searches, pertinent for that order?

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  • Do I have to learn html and javascript to create web applications?

    - by vainolo
    I am an experienced Java programmer, and I want to create a complex web application requiring dynamic pages, drawings, etc (take SO as an example). Do I have to learn javascript/html in order to create such an application? It is not that I don't want to learn another language (I've done this before), but technology on the javascript environment seems to change so fast that when you finish learning one framework it is already obsolete. I have checked a number of java framework for web development (spring, play), but not deeply. So can these frameworks (or other possible java frameworks that I'm not aware of) be used without learning html/javascript? I also have some python experience. So if I can do the app in python it is also an option.

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  • Java Cloud Service for developers

    - by JuergenKress
    The advent of cloud computing has reinvented application development for many companies. “That’s the beauty of the cloud,” says Cameron Purdy, vice president of development, Oracle. “It dramatically improves developer productivity because they can do what they do best without having to manage complex development, testing, staging, and production environments.” The key is to find a platform that doesn’t impose proprietary restrictions or force developers to learn new tools. For example, Oracle Java Cloud Service is an enterprise-grade platform as a service for building and deploying Java EE, Oracle WebLogic Server, and Oracle Application Development Framework (Oracle ADF) applications. “It’s designed to be flexible and easy to use,” says Purdy. “And it is also a standards-based solution -it’s not proprietary and there is no cloud lock-in. Developers get instant access to an enterprise-grade environment for a simple, monthly subscription.” Oracle Java Cloud Service instances are created with just a few clicks, so businesses can create a rich application development environment within minutes. Running on Oracle WebLogic Server and Oracle Exalogic, the underlying infrastructure also leverages Oracle Fusion Middleware’s integration with common services. For example, instances come integrated and preconfigured with optimized Oracle Database and Oracle Identity Management configurations. Based on Oracle Enterprise Manager, the Oracle Java Cloud Service console lets customers easily manage and monitor their Oracle Java Cloud Service instances. The open nature of the Oracle Java Cloud Service lets developers integrate through Web services such as SOAP and REST APIs, as well as use their favorite developer tools, whether they are out-of-the-box tools such as Maven and Ant or the productivity features built into Oracle JDeveloper, Oracle Enterprise Pack for Eclipse, or NetBeans IDE. The service allows for the seamless movement of applications between on-premise Oracle WebLogic Server domains and instances of Oracle Java Cloud Service within Oracle Cloud. This approach allows flexibility to mix and match the use of on-premise environments with cloud instances for development, test, and production environments. Visit to learn more and watch videos about Oracle Java Cloud Service. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. BlogTwitterLinkedInMixForumWiki Technorati Tags: java,cloud,oracle cloud,java cloud,WebLogic Community,Oracle,OPN,Jürgen Kress

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  • If most of team can't follow the architecture, what do you do?

    - by Chris
    Hi all, I'm working on a greenfields project with two other developers. We're all contractors, and myself and one other just started working on the project while the orginal one has been doing most of the basic framework coding. In the past month, my fellow programmer and I have been just frustrated by the design descisions done by our co-worker. Here's a little background information: The application at face value appeared to be your standard n-layered web application using C# on the 3.5 framework. We have a data layer, business layer and a web interface. But as we got deeper into the project we found some very interesting things that have caused us some troubles. There is a custom data access sqlHelper type base which only accepts dictionary key/valued entries and returns only data tables. There are no entity objects, but there are some massive objects which do everything and then are tossed into session for persitance. The general idea is that the pages (.aspx) don't do anything, while the controls (.ascx) do everything. The general flow is that a client clicks on a button, which goes to a user control base which passes a process request to the 'BLL' class which goes to the page processor, which then goes to a getControlProcessor, which at last actually processes the request. The request itself is made up of a dictionary which is passing a string valued method name, stored procedure name, a control name and possibly a value. All switching of the processing is done by comparing the string values of the control names and method names. Pages are linked together via a common header control that uses a combination of javascript and tables to create a hyperlink effect. And as I found out yesterday, a simple hyperlink between one page and another does not work because of the need to have quite a bit of information in session to determine which control to display on a page. My fellow programmer and I both believe that this is a strange and uncommon approach to web application development. Both of us have been in this business for over five years and neither of us have seen this approach. My question is this, how would we approach our co-worker and voice our concerns and what should we do if he does not want to accept the criteic? We both do not want to insult the work that has been done, but feel that going forward will create a nightmare for development. Thanks for your comments.

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  • Looking for PHP/MySQL-based ad manager

    - by user359650
    Could you recommend based on your experience a PHP/MySQL-based admin interface for managing your website ads? In order to be really useful, such application should have: -basic CRM functionality to track who is providing the ads -multilingual multi country support: have the ability to specify for the same ad, different versions for multiple languages/countries -predefined ad formats (google Ads, flash ads...) and sizes with corresponding PHP helpers so as to insert in the HTML code the necessary markup to properly integrate the ad. Ideally if that application could be desgined for Zend Framework that would be awesome (but I think I'm dreaming at this point).

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  • How do I succesfully compile Slingshot?

    - by Tigull
    I've been trying to compile Slingshot for a preview of Elementary OS. Even after replacing Gtk.Stock.CLEAR and Gtk.Stock.add with Gtk.STOCK_CLEAR and Gtk.Stock_add in slingshot/widget/entries .vala I still get the following error when executing sudo ./build_run: frontend/widgets/Entries.vala:130.13-130.25: error: The name `Stock_add' does not exist in the context of `Gtk' Gtk.Stock_add ({stock_item}); ^^^^^^^^^^^^^ Compilation failed: 1 error(s), 0 warning(s) mv: cannot stat `slingshot': No such file or directory ./build_run: 7: slingshot: not found I haven't found yet a soulution, therefore any help is appreciated, thanks!

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  • What is going on in this SAT/vector projection code?

    - by ssb
    I'm looking at the example XNA SAT collision code presented here: http://www.xnadevelopment.com/tutorials/rotatedrectanglecollisions/rotatedrectanglecollisions.shtml See the following code: private int GenerateScalar(Vector2 theRectangleCorner, Vector2 theAxis) { //Using the formula for Vector projection. Take the corner being passed in //and project it onto the given Axis float aNumerator = (theRectangleCorner.X * theAxis.X) + (theRectangleCorner.Y * theAxis.Y); float aDenominator = (theAxis.X * theAxis.X) + (theAxis.Y * theAxis.Y); float aDivisionResult = aNumerator / aDenominator; Vector2 aCornerProjected = new Vector2(aDivisionResult * theAxis.X, aDivisionResult * theAxis.Y); //Now that we have our projected Vector, calculate a scalar of that projection //that can be used to more easily do comparisons float aScalar = (theAxis.X * aCornerProjected.X) + (theAxis.Y * aCornerProjected.Y); return (int)aScalar; } I think the problems I'm having with this come mostly from translating physics concepts into data structures. For example, earlier in the code there is a calculation of the axes to be used, and these are stored as Vector2, and they are found by subtracting one point from another, however these points are also stored as Vector2s. So are the axes being stored as slopes in a single Vector2? Next, what exactly does the Vector2 produced by the vector projection code represent? That is, I know it represents the projected vector, but as it pertains to a Vector2, what does this represent? A point on a line? Finally, what does the scalar at the end actually represent? It's fine to tell me that you're getting a scalar value of the projected vector, but none of the information I can find online seems to tell me about a scalar of a vector as it's used in this context. I don't see angles or magnitudes with these vectors so I'm a little disoriented when it comes to thinking in terms of physics. If this final scalar calculation is just a dot product, how is that directly applicable to SAT from here on? Is this what I use to calculate maximum/minimum values for overlap? I guess I'm just having trouble figuring out exactly what the dot product is representing in this particular context. Clearly I'm not quite up to date on my elementary physics, but any explanations would be greatly appreciated.

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  • Maximizing the Value of Oracle Applications using Oracle Fusion Middleware

    Hear about the latest strategies for maximizing the value of your Oracle Applications using technologies in Oracle Fusion Middleware. Today's businesses recognize that to be more innovative with their business applications, they need to shorten their application implementations, eliminate brittle integrations and develop a simpler approach to securing and managing their applications. In this podcast we'll hear techniques for extending the reach of applications through improved user experience and collaboration, create application extensions that minimize the risk during upgrades, and make more informed decisions with integrated business intelligence. These approaches applied with Oracle Fusion Middleware and Oracle Applications can help lower TCO and provide rapid returns for your business.

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  • Securing the Tabular BI Semantic Model

    This paper introduces the security model for tabular BI semantic models in SQL Server 2012. You will learn how to create roles, implement dynamic security, configure impersonation settings, manage roles, and choose a method for connecting to models that works in your network security context. New! SQL Monitor 3.0 Red Gate's multi-server performance monitoring and alerting tool gets results from Day One.Simple to install and easy to use – download a free trial today.

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  • Unity3D or UDK or OPENGL from scratch?

    - by Legolas
    I am just very confused which I should choose in terms of high end game development. The application that I am designing is pretty simple, requires some 3D, and some effects. I am looking at a game similar to ping pong, but with high textures and graphics. I will just need web services to submit high scores. From my description, you can see that its pretty straight forward and I am confused whether I should use Unity3D or UDK or write the entire application myself with openGL (which will take a lot of time though). If you had faced this dilemma before, and chose for a particular graphics engine, please provide your suggestions and reasons as to why that was better. It would be helpful. Also, how can this affect in terms of investment and revenue ?

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  • Backward Compatibility with Silverlight 4 applications

    Each release of Silverlight it is the goal to make sure existing Silverlight applications continue to work. Since I think what this means causes some confusion Im going to do my best to explain what we mean by this. Silverlight 3 application working with Silverlight 4 Okay, scenario 1 is I have a Silverlight 3 application (XAP), will that still work as-is in Silverlight 4? Yes, this is the situation we refer to as backward compatibility. What this means is that existing compiled XAPs under previous...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • System bar not showing when using the macbuntu theme

    - by black sensei
    i think i really need your assistance in this.I've installed ubuntu 10.10 and this mac theme and so far it works fine. This morning i upgraded to 11.04 and it also went well. i just realise some of the effects were gone. so i open compizconfig settings manager, i've tried to enable the destop cube and the expo and it prompted me of desabling somethings here and there. honestly i went fast couldn't undo what i've done and i realize the new application launcher and the system bar weren't showing properly, so i decided to restart my machine.After that 'bummer', nothing were like before.no system bar, no application launcher, not menu bar for any of my applications not even for the console. How i'm going to solve this one this time. thanks for reading this and specially for helping out.

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  • Good technologies for developing a modular server component in .net?

    - by nubbers
    I am using WPF, Prism and Unity to develop the user interface for a .net application. The UI will run from a PC, but I also need to develop a separate complex server component that will provide services to the PC component via WCF. Prism and Unity have proved to be of great value in creating a modular application, at least as far as the user interface is concerned. I would also like to make the server component modular, but I cannot find anywhere what techniques, patterns and technologies are suitable. I have considered: Unity or one of the other DI containers Selected parts of Prism, such as modules and events Are these suitable for developing a modular server component? Or are these UI technologies only and should I be looking at something completely different?

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