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  • an example of schrödinbug?

    - by Pacerier
    This wiki page tells : A schrödinbug is a bug that manifests only after someone reading source code or using the program in an unusual way notices that it never should have worked in the first place, at which point the program promptly stops working for everybody until fixed. The Jargon File adds: "Though... this sounds impossible, it happens; some programs have harbored latent schrödinbugs for years." I've no idea what they are talking about. Can someone provide an example of how it is like (like with a fictional situation)?

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  • How to import ejb project classes into web project on eclipse?

    - by Jhonnytunes
    I have 3 projects on eclipse, maven ejb project, maven wicket webapp project and a enterprise application project that includes ejb and web I mentioned before, as modules. But my question is, How from my web project can I use classes on the ejb project. Lets say ClassA is on the ejb project and I want to say from web project: ClassA cl = new ClassA. I wont be allowed since web project doesnt have ClassA but ejb project. I want to use ejb project as a Business Logic, JPA part. Also I want to include here some not beans classes that I want to use from the web. Dont know if its possible. The web project goes without Business logic, just the wicket pages calling ejb, and using ther classes. Im new in the EE world. Never made an ear file including a war and ejb jar for deploying it on Glassfish. Thanks in advanced.

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  • How are Implicit-Heap dynamic Storage Binding and Dynamic type binding similar?

    - by Appy
    "Concepts of Programming languages" by Robert Sebesta says - Implicit Heap-Dynamic Storage Binding: Implicit Heap-Dynamic variables are bound to heap storage only when they are assigned values. It is similar to dynamic type binding. Can anyone explain the similarity with suitable examples. I understand the meaning of both the phrases, but I am an amateur when it comes to in-depth details.

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  • When is a Use Case layer needed?

    - by Meta-Knight
    In his blog post The Clean Architecture Uncle Bob suggests a 4-layer architecture. I understand the separation between business rules, interfaces and infrastructure, but I wonder if/when it's necessary to have separate layers for domain objects and use cases. What added value will it bring, compared to just having the uses cases as "domain services" in the domain layer? The only useful info I've found on the web about a use case layer is an article by Martin Fowler, who seems to contradict Uncle Bob about its necessity: At some point I may run into the problems, and then I'll make a Use Case Controller - but only then. And even when I do that I rarely consider the Use Case Controllers to occupy a separate layer in the system architecture. Edit: I stumbled upon a video of Uncle Bob's Architecture: The Lost Years keynote, in which he explains this architecture in depth. Very informative.

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  • Absolute beginner to app developement [closed]

    - by Andrew Johnston
    I have two app ideas that I am trying to build. I have started at the Facebook developement pages and done the Heroku/Git thing. However, I have absolutely no idea of what I am doing. When they say on the developer page: follow these quick easy steps Are they assuming that they are talking to a programmer/developer? I believe my apps have huge potential but I don't want to disclose my ideas. Any advice? I also would like to know how does one make money from Facebook applications?

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  • Exposing warnings\errors from data objects (that are also list returned)

    - by Oren Schwartz
    I'm exposing Data objects via service oriented assembly (which on future usages might become a WCF service). The data object is tree designed, as well as formed from allot of properties.Moreover, some services return one objects, others retrieve a list of them (thus disables throwing exceptions). I now want to expose data flow warnings and wondering what's the best way to do it having to things to consider: (1) seperation (2) ease of access. On the one hand, i want the UI team to be able to access a fields warnings (or errors) without having them mapping the field names to an external source but on the other hand, i don't want the warnings "hanged" on the object itself (as i don't see it a correct design). I tought of creating a new type of wrapper for each field, that'll expose events and they'll have to register the one's they care about (but totally not sure) I'll be happy to hear your thoughts. Could you please direct me to a respectful design pattern ? what dp will do best here ? Thank you very much!

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  • what is message passing in OO?

    - by Tom
    I've been studying OO programming, primarily in C++, C# and Java. I thought I had a good grasp on it with my understanding of encapsulation, inheritance and polymorphism (as well as reading a lot of questions on this site). One thing that seems to popup up here and there is the concept of "message passing". Apparently, this is something that is not used whilst OO programming in today's mainstream languages, but is supported by Smalltalk. My questions are: What is message passing? (Can someone give a practical example?) Is there any support for this "message passing" in C++, C# or Java?

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  • Good resources for language design

    - by Aaron Digulla
    There are lots of books about good web design, UI design, etc. With the advent of Xtext, it's very simple to write your own language. What are good books and resources about language design? I'm not looking for a book about compiler building (like the dragon book) but something that answers: How to create a grammar that is forgiving (like adding optional trailing commas)? Which grammar patterns cause problems for users of a language? How create a compact grammar without introducing ambiguities

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  • How to explain a layperson why a developer should not be interrupted while neck-deep in coding?

    - by András Szepesházi
    If you just consider the second part of my question, "Why a developer should not be interrupted while neck-deep in coding", that has been discussed a number of times by smart people. Heck, even the co-founder of SO, Joel Spolsky, wrote a blog post about "getting in the zone" and "being knocked out of the zone" and why it takes an average of 15 minutes to achieve productivity when participating in complex, software development related tasks. So I think the why has been established. What I'm interested in is how to explain all that to somebody who doesn't know beans about Beans (khmm I mean software development). How to tell the wife, or the funny guy from accounting at the workplace, or the long time friend who pings you on Skype every 30 minutes with a "Wazzzzzzup?!", that all the interruptions have a much deeper impact on your work than the obvious 30 seconds they took from your time. Obviously you can't explain it by sentences like "I have to juggle a lot of variable names in my short term memory" unless you want to be the target of blank stares or friendly abuse. I'd like to be able to explain all that to non-developers in a way that will make them clearly understand - without being offensive, elitist or too technical.

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  • Quantifying the value of refactoring in commercial terms

    - by Myles McDonnell
    Here is the classic scenario; Dev team build a prototype. Business mgmt like it and put it into production. Dev team now have to continue to deliver new features whilst at the same time pay the technical debt accrued when the code base was a prototype. My question is this (forgive me, it's rather open ended); how can the value of the refactoring work be quantified in commercial terms? As developers we can clearly understand and communicate the value in technical terms, such a the removal of code duplication, the simplification of an object model and so on. But this means little to an executive focussed on the commercial elements. What will mean something to this executive is the dev. team being able to deliver requirements at faster velocity. Just making this statement without any metrics that clearly quantify return on investment (increased velocity in return for resource allocated to refactoring) carries little weight. I'm interested to hear from anyone who has had experience, positive or negative, in relation to the above. ----------------- EDIT ---------------- Thanks for the responses so far, all of which I think are good. What I want to develop is a metric that proves (or disproves!) all of these statements. A report that ties velocity to refactoring and shows a positive effect.

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  • Should I ditch AJAX in client side web development when I've got a web-socket open?

    - by jt0dd
    I was thinking that maybe I should forget AJAX (HTTP) requests when I've got a web-socket open between client and server, but I decided I should ask here to check if this could be a bad practice for some reason that I'm not thinking of. Once the socket is open, there's less syntax (often meaning simpler error handling) involved in passing information between client and server with Socket.io (just one example of a web-socket). Is there some obvious situation where a web-socket (Socket.io for example) isn't going to be capable of handling a functionality that an AJAX request could do easily?

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  • History of open source software

    - by Victor Sorokin
    I've been always interested, out of the pure self-amusement, in the history of open software used today: who were the people which started it and what were the reasons to start what were design decisions at the start how software evolved over the time Specifically, I'm interested in following software: GCC X Linux kernel Java Of course, there is plenty of information in Internet to google for, but I thought it would be nice to have list of interesting resources at this site. I hope some of visitors of this site have similar interest and can share a link or two they found particularly amusing/interesting. To make this entry more question-like, here's straight question: what are the most interesting/amusing links about history of open source software?

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  • OOP concept: is it possible to update the class of an instantiated object?

    - by Federico
    I am trying to write a simple program that should allow a user to save and display sets of heterogeneous, but somehow related data. For clarity sake, I will use a representative example of vehicles. The program flow is like this: The program creates a Garage object, which is basically a class that can contain a list of vehicles objects Then the users creates Vehicles objects, these Vehicles each have a property, lets say License Plate Nr. Once created, the Vehicle object get added to a list within the Garage object --Later on--, the user can specify that a given Vehicle object is in fact a Car object or a Truck object (thus giving access to some specific attributes such as Number of seats for the Car, or Cargo weight for the truck) At first sight, this might look like an OOP textbook question involving a base class and inheritance, but the problem is more subtle because at the object creation time (and until the user decides to give more info), the computer doesn't know the exact Vehicle type. Hence my question: how would you proceed to implement this program flow? Is OOP the way to go? Just to give an initial answer, here is what I've came up until now. There is only one Vehicle class and the various properties/values are handled by the main program (not the class) through a dictionary. However, I'm pretty sure that there must be a more elegant solution (I'm developing using VB.net): Public Class Garage Public GarageAdress As String Private _ListGarageVehicles As New List(Of Vehicles) Public Sub AddVehicle(Vehicle As Vehicles) _ListGarageVehicles.Add(Vehicle) End Sub End Class Public Class Vehicles Public LicensePlateNumber As String Public Enum VehicleTypes Generic = 0 Car = 1 Truck = 2 End Enum Public VehicleType As VehicleTypes Public DictVehicleProperties As New Dictionary(Of String, String) End Class NOTE that in the example above the public/private modifiers do not necessarily reflect the original code

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  • How do you cope with change in open source frameworks that you use for your projects?

    - by Amy
    It may be a personal quirk of mine, but I like keeping code in living projects up to date - including the libraries/frameworks that they use. Part of it is that I believe a web app is more secure if it is fully patched and up to date. Part of it is just a touch of obsessive compulsiveness on my part. Over the past seven months, we have done a major rewrite of our software. We dropped the Xaraya framework, which was slow and essentially dead as a product, and converted to Cake PHP. (We chose Cake because it gave us the chance to do a very rapid rewrite of our software, and enough of a performance boost over Xaraya to make it worth our while.) We implemented unit testing with SimpleTest, and followed all the file and database naming conventions, etc. Cake is now being updated to 2.0. And, there doesn't seem to be a viable migration path for an upgrade. The naming conventions for files have radically changed, and they dropped SimpleTest in favor of PHPUnit. This is pretty much going to force us to stay on the 1.3 branch because, unless there is some sort of conversion tool, it's not going to be possible to update Cake and then gradually improve our legacy code to reap the benefits of the new Cake framework. So, as usual, we are going to end up with an old framework in our Subversion repository and just patch it ourselves as needed. And this is what gets me every time. So many open source products don't make it easy enough to keep projects based on them up to date. When the devs start playing with a new shiny toy, a few critical patches will be done to older branches, but most of their focus is going to be on the new code base. How do you deal with radical changes in the open source projects that you use? And, if you are developing an open source product, do you keep upgrade paths in mind when you develop new versions?

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  • Preffered lambda syntax?

    - by Roger Alsing
    I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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  • Can't understand example using continuations

    - by Matt Fenwick
    I'm reading the r6rs Scheme report and am confused by the explanation of continuations (I find it to be too dense and lacking of examples for a beginner). What is this code doing and how does it evaluate to 4? Why does call/cc want an argument that's a function of one argument? How is call/cc's argument used? (+ 1 (call-with-current-continuation (lambda (escape) (+ 2 (escape 3))))) =? 4 This example is from section 1.11 - Continuations.

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  • Is Silverlight only for eye-candy, or does it have a use in business?

    - by Cyberherbalist
    Granted that Silverlight may make eye-popping websites of great beauty, is there any justification for using it to make practical web applications that have serious business purposes? I'd like to use it (to learn it) for a new assignment I have, which is to build a web-based application that keeps track of the data interfaces used in our organization, but I'm not sure how to justify it, even to myself. Any thoughts on this? If I can't justify it then I will have to build the app using the same old tired straight ASP.NET approach I've used (it seems) a hundred times already.

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  • Is it typical for a provider of a web services to also provide client libraries?

    - by HDave
    My company is building a corporate Java web-app and we are leaning towards using GWT-RPC as the client-server protocol for performance reasons. However, in the future, we will need to provide an API for other enterprise systems to access our data as well. For this, we were thinking of a SOAP based web service. In my experience it is common for commercial providers of enterprise web applications to provide client libraries (Java, .NET, C#, etc.). Is this generally the case? I ask because if so, then why bother using SOAP or REST or any standard web services protocol at all? Why not just create a client libraries that communicate via GWT-RPC?

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  • Using <= for every dependency in case of following semantic versioning idea

    - by zerkms
    As Semantic Versioning (and common sense) declares - the major version is incremented in case if non backward compatible change is introduced. Now let's assume we have a project called Project that has a current version 1.0.42 and a library Lib it depends on that is of a 2.1.3 version at the moment. Does that mean that following semver ideology we should constraint the dependency of the Project to be Depends: Lib (< 3)? From my experience - no one does that, but I find it semantically correct and very self-descriptive. What do you think of this?

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  • What makes signed integers behave differently?

    - by 000
    In this example of x86_64 hex/disassembled code I see: 48B80000000000000000 mov rax, 0x0 Signed Byte 52 Unsigned Byte 52 Signed Short 14388 Unsigned Short 14388 Signed Int 943863860 Unsigned Int 943863860 Signed Int64 3472328296363079732 Unsigned Int64 3472328296363079732 Float 4.630555e-05 Double 1.39804332763832e-76 String 48B80000000000000000 which to me appears to have the same functionality as: 48C7C000000000 mov rax, 0x0 48C7C000000000 Signed Byte 52 Unsigned Byte 52 Signed Short 14388 Unsigned Short 14388 Signed Int 927152180 Unsigned Int 927152180 Signed Int64 3472328377950746676 Unsigned Int64 3472328377950746676 Float 1.163599e-05 Double 1.39806836023098e-76 String 48C7C000000000 How is the first example treated differently from the second example?

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  • Configure Jenkins and Tomcat using Puppet

    - by ex3v
    I'm trying to setup Spring dev environment (jenkins, tomcat) on Vagrant. What I really want to achieve is to limit config to only Puppet scripts, so I can share it with my colleagues and work together on the same environment. So far I managed to set up simple scripts to install jenkins, tomcat and so on, they work fine. What about jenkins configuration though? I'm pretty green in jenkins usage and configuration, not sure if I'm doing it the right way... I found this article and I want to migrate whole setup described in it to Puppet. Any ideas? Thanks.

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  • How to design a scriptable communication emulator?

    - by Hawk
    Requirement: We need a tool that simulates a hardware device that communicates via RS232 or TCP/IP to allow us to test our main application which will communicate with the device. Current flow: User loads script Parse script into commands User runs script Execute commands Script / commands (simplified for discussion): Connect RS232 = RS232ConnectCommand Connect TCP/IP = TcpIpConnectCommand Send data = SendCommand Receive data = ReceiveCommand Disconnect = DisconnectCommand All commands implement the ICommand interface. The command runner simply executes a sequence of ICommand implementations sequentially thus ICommand must have an Execute exposure, pseudo code: void Execute(ICommunicator context) The Execute method takes a context argument which allows the command implementations to execute what they need to do. For instance SendCommand will call context.Send, etc. The problem RS232ConnectCommand and TcpIpConnectCommand needs to instantiate the context to be used by subsequent commands. How do you handle this elegantly? Solution 1: Change ICommand Execute method to: ICommunicator Execute(ICommunicator context) While it will work it seems like a code smell. All commands now need to return the context which for all commands except the connection ones will be the same context that is passed in. Solution 2: Create an ICommunicatorWrapper (ICommunicationBroker?) which follows the decorator pattern and decorates ICommunicator. It introduces a new exposure: void SetCommunicator(ICommunicator communicator) And ICommand is changed to use the wrapper: void Execute(ICommunicationWrapper context) Seems like a cleaner solution. Question Is this a good design? Am I on the right track?

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  • What icon would you use to denote an XML (not rss) feed available [closed]

    - by mplungjan
    Given two sites - one aimed at regular users and one for automated access. The first site is the best known, so many are (still) screen scraping that site for data. It is preferable to have move to the other site where the same data is available in xml format. What icon (+text/title) on a page you are about to screen scrape, would make you pay attention and decide to see what that was about? Examples from Google Image search for xml icon

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  • How broad should a computer science/engineering student go?

    - by AskQuestions
    I have less than 2 years of college left and I still don't know what to focus on. But this is not about me, this is about being a future developer. I realize that questions like "Which language should I learn next?" are not really popular, but I think my question is broader than that. I often see people write things like "You have to learn many different things. Being a developer is not about learning one programming language / technology and then doing that for the rest of your life". Well, sure, but it's impossible to really learn everything thoroughly. Does that mean that one should just learn the basics of everything and then learn some things more thoroughly AFTER getting a particular job? I mean, the best way to learn programming is by actually programming stuff... But projects take time. Does an average developer really switch between (for example) being a web developer, doing artificial intelligence and machine learning related stuff and programming close to the hardware? I mean, I know a lot of different things, but I don't feel proficient in any of those things. If I want to find a job as a web developer (that's just an example) after I finish college, shouldn't I do some web related project (maybe using something I still don't know) rather than try to learn functional programming? So, the question is: How broad should a computer science student's field of focus be? One programming language is surely far too narrow, but what is too broad?

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  • How should I update Ajax Control Toolkit in VS 2010?

    - by Soham
    Suppose if there is a new version available of Ajax Control Toolkit then how should I install/update it in my visual studio 2010 which has already install older version of same toolkit? I would like to install new one while older toolkit would totally uninstalled, because mostly new toolkit always has all controls that were in the old toolkit & also some new controls. Then 1) Should I've to remove .dll file in my toolkit installation folder and place new .dll file there? If I do so then will VS 2010 automatically delete older entries of toolkit controls in .NET Components list and place new control there? Or 2) Should I've to uninstall old toolkit manually i.e delete .dll file and uncheck all entries in .NET Components list & after that install new one from scratch?

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