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  • When do you use a struct instead of a class?

    - by jkohlhepp
    What are your rules of thumb for when to use structs vs. classes? I'm thinking of the C# definition of those terms but if your language has similar concepts I'd like to hear your opinion as well. I tend to use classes for almost everything, and use structs only when something is very simplistic and should be a value type, such as a PhoneNumber or something like that. But this seems like a relatively minor use and I hope there are more interesting use cases.

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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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  • Questioning the motivation for dependency injection: Why is creating an object graph hard?

    - by oberlies
    Dependency injection frameworks like Google Guice give the following motivation for their usage (source): To construct an object, you first build its dependencies. But to build each dependency, you need its dependencies, and so on. So when you build an object, you really need to build an object graph. Building object graphs by hand is labour intensive (...) and makes testing difficult. But I don't buy this argument: Even without dependency injection, I can write classes which are both easy to instantiate and convenient to test. E.g. the example from the Guice motivation page could be rewritten in the following way: class BillingService { private final CreditCardProcessor processor; private final TransactionLog transactionLog; // constructor for tests, taking all collaborators as parameters BillingService(CreditCardProcessor processor, TransactionLog transactionLog) { this.processor = processor; this.transactionLog = transactionLog; } // constructor for production, calling the (productive) constructors of the collaborators public BillingService() { this(new PaypalCreditCardProcessor(), new DatabaseTransactionLog()); } public Receipt chargeOrder(PizzaOrder order, CreditCard creditCard) { ... } } So dependency injection may really be an advantage in advanced use cases, but I don't need it for easy construction and testability, do I?

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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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  • Are there programming languages that allow you to do set arithmetic on types?

    - by Will Brown
    Out of curiosity, are there languages that allow you to do set arithmetic on types to create new types? Something like: interface A { void a(); void b(); } interface B { void b(); void c(); } interface C = A & B; // has b() interface D = A | B; // has a(), b() and c() interface E = (A & B) ^ B; // has c() I know that in some languages these ideas can be expressed (i.e., Java has List<Comparable & Serializable> for the union of the interfaces) but I've never heard of a language that supports type arithmetic. Thanks!

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  • Why is using C++ libraries so complicated?

    - by Pius
    First of all, I want to note I love C++ and I'm one of those people who thinks it is easier to code in C++ than Java. Except for one tiny thing: libraries. In Java you can simply add some jar to the build path and you're done. In C++ you usually have to set multiple paths for the header files and the library itself. In some cases, you even have to use special build flags. I have mainly used Visual Studio, Code Blocks and no IDE at all. All 3 options do not differ much when talking about using external libraries. I wonder why was there made no simpler alternative for this? Like having a special .zip file that has everything you need in one place so the IDE can do all the work for you setting up the build flags. Is there any technical barrier for this?

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  • How to design highly scalable web services in Java?

    - by Kshitiz Sharma
    I am creating some Web Services that would have 2000 concurrent users. The services are offered for free and are hence expected to get a large user base. In the future it may be required to scale up to 50,000 users. There are already a few other questions that address the issue like - Building highly scalable web services However my requirements differ from the question above. For example - My application does not have a user interface, so images, CSS, javascript are not an issue. It is in Java so suggestions like using HipHop to translate PHP to native code are useless. Hence I decided to ask my question separately. This is my project setup - Rest based Web services using Apache CXF Hibernate 3.0 (With relevant optimizations like lazy loading and custom HQL for tune up) Tomcat 6.0 MySql 5.5 My questions are - Are there alternatives to Mysql that offer better performance for what I'm trying to do? What are some general things to abide by in order to scale a Java based web application? I am thinking of putting my Application in two tomcat instances with httpd redirecting the request to appropriate tomcat on basis of load. Is this the right approach? Separate tomcat instances can help but then database becomes the bottleneck since both applications access the same database? I am a programmer not a Db Admin, how difficult would it be to cluster a Mysql database (or, to cluster whatever database offered as an alternative to 1)? How effective are caching solutions like EHCache? Any other general best practices? Some clarifications - Could you partition the data? Yes we could but we're trying to avoid it. We need to run a lot of data mining algorithms and the design would evolve over time so we can't be sure what lines of partition should be there.

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  • New code base, what experiences/recommendations do you have?

    - by hlovdal
    I will later this year start on a project (embedded hardware, C, small company) where I believe that most (if not all) code will be new. So what experiences do you have to share as advice to starting a new code base? What have you been missing in projects that you have been working on? What has worked really well? What has not worked? Let's limit this question to be about things that relate directly to the code (e.g "banning the use of gets()": in scope, version control: border line, build system: out of scope).

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  • DBMS agnostic - What to name the COUNT column from a SQL Query

    - by cyberkiwi
    I have trouble naming the COUNT() column from SQL queries and will swap between various variants _Count [Count] (sql, or "count" or backticks for MySQL etc) C Cnt CountSomething (where "something" is the field being counted, or "CountAll") NoOfRows RowCount etc Has anyone come up with any name that you are happy with and always use without hesitation? This is bothering me because after joining SO just recently, my answers have shown this tendency of flip-flopping with no consistency. I need to get this sorted. Please help. (While we're at it, what do you use for SUM etc?) Note: Before you close this question, consider that this one was not: What's the best name for a non-mutating “add” method on an immutable collection?

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  • what's included in a typical computer architecture class? [closed]

    - by sq1020
    Does this description fit what's usually included in a computer architecture class? Computer Organization and Assembly Language An introduction to the hardware organization and assembly language of the Intel processor. Topics include memory hierarchy and design- CPU design- pipelining- addressing modes- subroutine linkage- polled input/output- interrupts- high level language interfacing and macros.

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  • Is extensive documentation a code smell?

    - by Griffin
    Every library, open-source project, and SDK/API I've ever come across has come packaged with a (usually large) documentation file, and this seems contradictory to the wide-spread belief that good code needs little to no comments. What separates documentation from this programming methodology? a one to two page overview of a package seems reasonable, but elegant code combined with standard intelisense should have theoretically deprecated the practice of documentation by now IMO. I feel like companies only create detailed documentation and tutorials because its what they've always done. Why should developers have to constantly be searching through online documentation in order to learn how to do things when such information should be intrinsic to the classes, methods and namespaces?

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  • unit/integration testing web service proxy client

    - by cori
    I'm rewriting a PHP client/proxy library that provides an interface to a SOAP-based .Net webservice, and in the process I want to add some unit and integration tests so future modifications are less risky. The work the library I'm working on performs is to marshall the calls to the web service and do a little reorganizing of the responses to present a slightly more -object-oriented interface to the underlying service. Since this library is little else than a thin layer on top of web service calls, my basic assumption is that I'll really be writing integration tests more than unit tests - for example, I don't see any reason to mock away the web service - the work that's performed by the code I'm working on is very light; it's almost passing the response from the service right back to its consumer. Most of the calls are basic CRUD operations: CreateRole(), CreateUser(), DeleteUser(), FindUser(), &ct. I'll be starting from a known database state - the system I'm using for these tests is isolated for testing purposes, so the results will be more or less predictable. My question is this: is it natural to use web service calls to confirm the results of operations within the tests and to reset the state of the application within the scope of each test? Here's an example: One test might be createUserReturnsValidUserId() and might go like this: public function createUserReturnsValidUserId() { // we're assuming a global connection to the service $newUserId = $client->CreateUser("user1"); assertNotNull($newUserId); assertNotNull($client->FindUser($newUserId); $client->deleteUser($newUserId); } So I'm creating a user, making sure I get an ID back and that it represents a user in the system, and then cleaning up after myself (so that later tests don't rely on the success or failure of this test w/r/t the number of users in the system, for example). However this still seems pretty fragile - lots of dependencies and opportunities for tests to fail and effect the results of later tests, which I definitely want to avoid. Am I missing some options of ways to decouple these tests from the system under test, or is this really the best I can do? I think this is a fairly general unit/integration testing question, but if it matters I'm using PHPUnit for the testing framework.

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  • Recent programming language for AI?

    - by Eduard Florinescu
    For a few decades the programming language of choice for AI was either Prolog or LISP, and a few more others that are not so well known. Most of them were designed before the 70's. Changes happens a lot on many other domains specific languages, but in the AI domain it hadn't surfaced so much as in the web specific languages or scripting etc. Are there recent programming languages that were intended to change the game in the AI and learn from the insufficiencies of former languages?

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  • How can a computer render a CLI/console along with a GUI?

    - by Nathaniel Bennett
    I'm confused when looking into graphics - specifically with operating systems. I mean, how can a computer render a CLI/console along with a GUI? GUI's are completely different from text. And how can we have GUI windows that display text interfaces, ie how can we have CLI in modern Graphics Operating system - that's what I'm mainly trying to grip on to. How does graphics get rendered to display? Is there some sort of memory address that a GPU access which holds all pixel data, and there system's within OS's that gather the pixel position of windows and widgets, along with the Z Index and rasterize them to that memory address, which then the GPU loads to the screen? How about the CLI's integrated with Graphics? How does the OS tell the GPU that a certain part of the screen wants to display text while the rest wants to display pixel data?

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  • Nearly technical books that you enjoyed reading

    - by pablo
    I've seen questions about "What books you recommend" in several of the Stack Exchange verticals. Perhaps these two questions (a and b) are the most popular. But, I'd like to ask for recommendations of a different kind of books. I have read in the past "The Passionate Programmer" and I am now reading "Coders at Work". Both of them I would argue that are almost a biography (or biographies in the "Coders at work") or even a bit of "self-help" book (that is more the case of the "Passionate programmer"). And please don't get me wrong. I loved reading the first one, and I am loving reading the second one. There's a lot of value in it, mostly in "lessons of the trade" kind of way. So, here is what I'd like to know. What other books that you read that are similar to these ones in intent that you enjoyed? Why?

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  • Would you make your website's source code public?

    - by Karpie
    Back story: My best friend is a self-taught coder for a community art site, written in PHP. Some time ago he mentioned he wanted to make the source code of the site public, to which my response was total horror - surely it was going to be full of security holes waiting to be found, and it was going to lead to hacking and errors on a huge scale. He never ended up doing it. Current story: I'm starting development of a community website built in Rails, and for ease of use I was going to use Github for version control. Then I realized it was pretty much exactly the same thing as my friend making his source code public - which made me stop and think. Would you make your website's completely-custom source code public? Or is this a case of open source gone too far? (note: I don't think this applies to people who run things like Wordpress. Or does it?)

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  • WPF: Reloading app parts to handle persistence as well as memory management.

    - by Ingó Vals
    I created a app using Microsoft's WPF. It mostly handles data reading and input as well as associating relations between data within specific parameters. As a total beginner I made some bad design decision ( not so much decisions as using the first thing I got to work ) but now understanding WPF better I'm getting the urge to refactor my code with better design principles. I had several problems but I guess each deserves it's own question for clarity. Here I'm asking for proper ways to handle the data itself. In the original I wrapped each row in a object when fetched from database ( using LINQ to SQL ) somewhat like Active Record just not active or persistence (each app instance had it's own data handling part). The app has subunits handling different aspects. However as it was setup it loaded everything when started. This creates several problems, for example often it wouldn't be neccesary to load a part unless we were specifically going to work with that part so I wan't some form of lazy loading. Also there was problem with inner persistance because you might create a new object/row in one aspect and perhaps set relation between it and different object but the new object wouldn't appear until the program was restarted. Persistance between instances of the app won't be huge problem because of the small amount of people using the program. While I could solve this now using dirty tricks I would rather refactor the program and do it elegantly, Now the question is how. I know there are several ways and a few come to mind: 1) Each aspect of the program is it's own UserControl that get's reloaded/instanced everytime you navigate to it. This ensures you only load up the data you need and you get some persistancy. DB server located on same LAN and tables are small so that shouldn't be a big problem. Minor drawback is that you would have to remember the state of each aspect so you wouldn't always start at beginners square. 2) Having a ViewModel type object at the base level of the app with lazy loading and some kind of timeout. I would then propegate this object down the visual tree to ensure every aspect is getting it's data from the same instance 3) Semi active record data layer with static load methods. 4) Some other idea What in your opinion is the most practical way in WPF, what does MVVM assume?

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  • In Search of Automatic ORM with REST interface

    - by Dan Ray
    I have this wish that so far Google hasn't been able to fulfill. I want to find a package (ideally in PHP, because I know PHP, but I guess that's not a hard requirement) that you point at a database, it builds an ORM based on what it finds there, and exposes a REST interface over the web. Everything I've found in my searches requires a bunch of code--like, it wants you to build the classes for it, but it'll handle the REST request routing. Or it does database and relational stuff just fine, but you have to build your own methods for all the CRUD actions. That's dumb. REST is well defined. If I wanted to re-invent the wheel, I totally could, but I don't want to. Isn't there somebody who's built a one-shot super-simple auto-RESTing web service package?

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  • a little code to allow word substitution depending on user

    - by Fred Quimby
    Can anyone help? I'm creating a demo web app in html in order for people to physically see and comment on the app prior to committing to a proper build. So whilst the proper app will be database driven, my demo is just standard html with some javascript effects. What I do want to demonstrate is that different user group will see different words. For example, imagine I have an html sentence that says 'This will cost £100 to begin'. What I need to some way of identifying that if the user has deemed themselves to be from the US, the sentence says 'This will cost $100 to begin'. This requirement is peppered throughtout the pages but I'm happy to add each one manually. So I envisage some code along the lines of 'first, remove the [boot US] trunk' where the UK version is 'first remove the boot' but the code is saying that the visitor needs the US version. It then looks up boot (in an Access database perhaps) and sees that the table says for boot for US, display 'trunk'. I'm not a programmer but I can normally cobble together scripts so I'm hoping someone may have a relatively easy solution in javascrip, CSS or asp. To recap; I have a number of words or short sentences that need to appear differently and I'm happy to manually insert each one if necessary (but would be even better if the words were automatically changed). And I need a device which allows me to tell the pages to choose the US version, or for example, the New Zealand version. Thanks in advance. Fred

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  • Object-Oriented Operating System

    - by nmagerko
    As I thought about writing an operating system, I came across a point that I really couldn't figure out on my own: Can an operating system truly be written in an Object-Oriented Programming (OOP) Language? Being that these types of languages do not allow for direct accessing of memory, wouldn't this make it impossible for a developer to write an entire operating system using only an OOP Language? Take, for example, the Android Operating System that runs many phones and some tablets in use around the world. I believe that this operating system uses only Java, an Object-Oriented language. In Java, I have been unsuccessful in trying to point at and manipulate a specific memory address that the run-time environment (JRE) has not assigned to my program implicitly. In C, C++, and other non-OOP languages, I can do this in a few lines. So this makes me question whether or not an operating system can be written in an OOP, especially Java. Any counterexamples or other information is appreciated.

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  • Would you refactor this and if so, would you charge your client?

    - by Julius
    I am working on a freelance job at home. The client wants me to write some new functionality for his CMS, but it is taking me a lot of time to figure out what the code is doing, because it is written in a very unreadable style. Below is just an example of what I mean. The previous programmer made extensive use of anonymous functions, of eval(), he uses deeply nested ternary operators, he didn't indent code, didn't use comments, and he uses funny constructions like misusing the behaviour of logical operators || and && for creating if/else conditions (the second condition of && only gets tested if the first one is true, opening the possibility to use && as an if/else construction). All in all it's insane code and it's costing me a lot of time to find out how the current code works. return ($this->main->context != "ajax" || in_array($this->type, $this->definition->ajax)) ? eval('return method_exists($this,"Show'.ucfirst($this->type).'") ? $this->Show'.ucfirst($this->type).'('.(count($args) ? join(",",array_map(create_function('$a','return (is_numeric($a) || preg_match("/^array/",$a)) ? $a : "\"".$a."\"";'),$args)) : "").') : null;') : ''; Would you refactor this code and how would you handle this sort of thing with your client, I mean financially?

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  • How to keep AST for feature access?

    - by greenoldman
    Consider such code (let's say it is C++) Foo::Bar.get().X How one should keep the AST for this -- as "tree" with root at left Foo(Bar(get(X)), or with root at right (((Foo)Bar)get)X? Or maybe as a flat structure (list)? The first one seems more convenient when resolving names, the second when working with it as expression. I set tag parsing but I am asking from semantic analysis POV really (there is no such tag).

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  • how a pure functional programming language manage without assignment statements?

    - by Gnijuohz
    When reading the famous SICP,I found the authors seem rather reluctant to introduce the assignment statement to Scheme in Chapter 3.I read the text and kind of understand why they feel so. As Scheme is the first functional programming language I ever know something about,I am kind of surprised that there are some functional programming languages(not Scheme of course) can do without assignments. Let use the example the book offers,the bank account example.If there is no assignment statement,how can this be done?How to change the balance variable?I ask so because I know there are some so-called pure functional languages out there and according to the Turing complete theory,this must can be done too. I learned C,Java,Python and use assignments a lot in every program I wrote.So it's really an eye-opening experience.I really hope someone can briefly explain how assignments are avoided in those functional programming languages and what profound impact(if any) it has on these languages. The example mentioned above is here: (define (make-withdraw balance) (lambda (amount) (if (>= balance amount) (begin (set! balance (- balance amount)) balance) "Insufficient funds"))) This changed the balance by set!.To me it looks a lot like a class method to change the class member balance. As I said,I am not familiar with functional programming languages,so if I said something wrong about them,feel free to point out.

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  • kill SIGABRT does not generate core file from daemon started from crontab. [closed]

    - by Guma
    I am running CentOS 5.5 and working on server application that sometimes I need to force core dump so I can see what is going on. If I start my server from shell and send kill SIGABRT, core file is created. If I start same program from crontab and than I send same signal to it server is "killed" but not core file is generated. Does any one know why is that and what need to be added to my code or changed in system settings to allow core file generation? Just a side note I have ulimit set to unlimited in /etc/profile I have set kernel.core_uses_pid = 1 kernel.core_pattern=/var/cores/%h-%e-%p.core in /etc/sysctl.conf Also my server app was added to crontab under same login id as I am running it from shell. Any help greatly appreciated

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  • Effective template system

    - by Alex
    I'm building a content management system, and need advice on which theming structure should I adopt. A few options (This is not a complete list): Wordpress style: the controller decides what template to load based on the user request, like: home page / article archive / single article page etc. each of these templates are unrelated to other templates, and must exist within the theme the theme developer decides if (s)he want to use inner-templates (like "sidebar", "sidebar item"), and includes them manually where (s)he thinks are needed. Drupal style: the controller gives control to the theme developer only to inner-templates; if they don't exist it falls back internally to some default templates (I find this very restrictive) Funky style: the controller only loads a "index.php" template and provides the theme developer conditional tags, which he can use to include inner-templates if (s)he wants. Among these styles, or others what style of template system allows for fast development and a more concise design and implementation.

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