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  • "Public" nested classes or not

    - by Frederick
    Suppose I have a class 'Application'. In order to be initialised it takes certain settings in the constructor. Let's also assume that the number of settings is so many that it's compelling to place them in a class of their own. Compare the following two implementations of this scenario. Implementation 1: class Application { Application(ApplicationSettings settings) { //Do initialisation here } } class ApplicationSettings { //Settings related methods and properties here } Implementation 2: class Application { Application(Application.Settings settings) { //Do initialisation here } class Settings { //Settings related methods and properties here } } To me, the second approach is very much preferable. It is more readable because it strongly emphasises the relation between the two classes. When I write code to instantiate Application class anywhere, the second approach is going to look prettier. Now just imagine the Settings class itself in turn had some similarly "related" class and that class in turn did so too. Go only three such levels and the class naming gets out out of hand in the 'non-nested' case. If you nest, however, things still stay elegant. Despite the above, I've read people saying on StackOverflow that nested classes are justified only if they're not visible to the outside world; that is if they are used only for the internal implementation of the containing class. The commonly cited objection is bloating the size of containing class's source file, but partial classes is the perfect solution for that problem. My question is, why are we wary of the "publicly exposed" use of nested classes? Are there any other arguments against such use?

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  • Resources for Programmatic Rendering of Topology Maps

    - by bn
    Servus, Do you know of any frameworks, APIS, languages, or other resources that are well suited for drawing topology maps that allow a user to interact with objects on the map? I am not constrained by language choice and the program can be web-based, or stand-alone. I thought I would check before rolling my own. My goal is not to draw cartographic maps, but more like this picture: http://www.fineconnection.com/files/images/GraphicalNM.PNG, or if you are familiar with Edward Tufte's books, the data-visualization mechanisms he describes such as a map of a metro or subway. Also, if you have had any experience rendering these types of user interfaces or usage of underlying datastructures, I would be grateful to hear any thoughts you have on the subject, advice, any "gotchas." Thank you very for your time, -bn

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  • iphone: caching and updating xml fields

    - by pJosh
    Thanks for your help. Here I have another question. I get the data through XMLParsing, now I want to store it in iphone's cache, and the XML Fields are updates every 12 hours.how can i check that XML Fields are change or not? and how can I store the data in iphone's cache memory so that evry it does not has to interact with web. Can anybody please help me???

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  • MVC pattern and State Machine

    - by topright
    I think of a game as a state machine. Game States separate I/O processing, game logic and rendering into different classes: while (game_loop) { game->state->io_events(this); game->state->logic(this); game->state->rendering(); } You can easily change a game state in this approach. MVC separation works in more complex way: while (game_loop) { game->cotroller->io_events(this); game->model->logic(this); game->view->rendering(); } So changing Game States becomes error prone task (switch 3 MVC objects, not 1). What are practical ways of combining these 2 concepts?

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  • Light-weight client/server DB?

    - by OverTheRainbow
    Hello, (This question falls between programming and finding a tool, so I guess I'll ask here in SO since it has more activity than SuperUser.) I like the simplicity of SQLite, but by design, it doesn't support concurrent access. The apps I write don't have heavy needs, so I'd like to avoid heavier solutions like MySQL that are more difficult to deploy (remote customers with usually no computer personnel). Does someone know of a good solution that would offer the following features? Client available for VB.Net applications The server itself doesn't have to be a .Net application. Actually, I'd rather a bare-metal server so that it can run even on embedded Linux hosts with less RAM/CPU than regular PC's Easy install: the client part should either be statically linked inside the client application or be available as a single DLL, and the server should just be a single EXE listening for queries, à la Fossil (http://www.fossil-scm.org) clients can locate the server on the LAN by broadcasting data picked up by the server, so users don't have to write down the IP address and paste it into each client open-source, or moderately priced closed-source Thank you.

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  • Register all GUI components as Observers or pass current object to next object as a constructor argu

    - by Jack
    First, I'd like to say that I think this is a common issue and there may be a simple or common solution that I am unaware of. Many have probably encountered a similar problem. Thanks for reading. I am creating a GUI where each component needs to communicate (or at least be updated) by multiple other components. Currently, I'm using a Singleton class to accomplish this goal. Each GUI component gets the instance of the singleton and registers itself. When updates need to be made, the singleton can call public methods in the registered class. I think this is similar to an Observer pattern, but the singleton has more control. Currently, the program is set up something like this: class c1 { CommClass cc; c1() { cc = CommClass.getCommClass(); cc.registerC1( this ); C2 c2 = new c2(); } } class c2 { CommClass cc; c2() { cc = CommClass.getCommClass(); cc.registerC2( this ); C3 c3 = new c3(); } } class c3 { CommClass cc; c3() { cc = CommClass.getCommClass(); cc.registerC3( this ); C4 c4 = new c4(); } } etc. Unfortunately, the singleton class keeps growing larger as more communication is required between the components. I was wondering if it's a good idea to instead of using this singleton, pass the higher order GUI components as arguments in the constructors of each GUI component: class c1 { c1() { C2 c2 = new c2( this ); } } class c2 { C1 c1; c2( C1 c1 ) { this.c1 = c1 C3 c3 = new c3( c1, this ); } } class c3 { C1 c1; C2 c2; c3( C1 c1, C2 c2 ) { this.c1 = c1; this.c2 = c2; C4 c4 = new c4( c1, c2, this ); } } etc. The second version relies less on the CommClass, but it's still very messy as the private member variables increase in number and the constructors grow in length. Each class contains GUI components that need to communicate through CommClass, but I can't think of a good way to do it. If this seems strange or horribly inefficient, please describe some method of communication between classes that will continue to work as the project grows. Also, if this doesn't make any sense to anyone, I'll try to give actual code snippets in the future and think of a better way to ask the question. Thanks.

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  • Re-using aggregate level formulas in SQL - any good tactics?

    - by Cade Roux
    Imagine this case, but with a lot more component buckets and a lot more intermediates and outputs. Many of the intermediates are calculated at the detail level, but a few things are calculated at the aggregate level: DECLARE @Profitability AS TABLE ( Cust INT NOT NULL ,Category VARCHAR(10) NOT NULL ,Income DECIMAL(10, 2) NOT NULL ,Expense DECIMAL(10, 2) NOT NULL ) ; INSERT INTO @Profitability VALUES ( 1, 'Software', 100, 50 ) ; INSERT INTO @Profitability VALUES ( 2, 'Software', 100, 20 ) ; INSERT INTO @Profitability VALUES ( 3, 'Software', 100, 60 ) ; INSERT INTO @Profitability VALUES ( 4, 'Software', 500, 400 ) ; INSERT INTO @Profitability VALUES ( 5, 'Hardware', 1000, 550 ) ; INSERT INTO @Profitability VALUES ( 6, 'Hardware', 1000, 250 ) ; INSERT INTO @Profitability VALUES ( 7, 'Hardware', 1000, 700 ) ; INSERT INTO @Profitability VALUES ( 8, 'Hardware', 5000, 4500 ) ; SELECT Cust ,Profit = SUM(Income - Expense) ,Margin = SUM(Income - Expense) / SUM(Income) FROM @Profitability GROUP BY Cust SELECT Category ,Profit = SUM(Income - Expense) ,Margin = SUM(Income - Expense) / SUM(Income) FROM @Profitability GROUP BY Category SELECT Profit = SUM(Income - Expense) ,Margin = SUM(Income - Expense) / SUM(Income) FROM @Profitability Notice how the same formulae have to be used at the different aggregation levels. This results in code duplication. I have thought of using UDFs (either scalar or table valued with an OUTER APPLY, since many of the final results may share intermediates which have to be calculated at the aggregate level), but in my experience the scalar and multi-statement table-valued UDFs perform very poorly. Also thought about using more dynamic SQL and applying the formulas by name, basically. Any other tricks, techniques or tactics to keeping these kinds of formulae which need to be applied at different levels in sync and/or organized?

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  • adding one time options to items

    - by rap-uvic
    Hello, I'm building an Event Registration site. For any given event, we'll have a handful of items to choose from. I have a table for these items. For each event we might have special options for users. For example, for one of the events new users get to buy an item which is not available to other users. This may not apply to all the events. For other events we might have some other restriction on items. I will obviously be checking this programmatically on application side. I would like to though, set up a column containing flag in the items table. But I don't find it feasible because this condition may only apply to one particular event. I don't want all the future items to have this column. What is a good approach to take in such a situation? Should I create a special "restrictions" table and just do a join? How would I handle this on the application side?

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  • SDL side-scroller scrolls inconsistantly

    - by SDLFunTimes
    So I'm working on an upgrade from my previous project (that I posted here for code review) this time implementing a repeating background (like what is used on cartoons) so that SDL doesn't have to load really big images for a level. There's a strange inconsistency in the program, however: the first time the user scrolls all the way to the right 2 less panels are shown than is specified. Going backwards (left) the correct number of panels is shown (that is the panels repeat the number of times specified in the code). After that it appears that going right again (once all the way at the left) the correct number of panels is shown and same going backwards. Here's some selected code and here's a .zip of all my code constructor: Game::Game(SDL_Event* event, SDL_Surface* scr, int level_w, int w, int h, int bpp) { this->event = event; this->bpp = bpp; level_width = level_w; screen = scr; w_width = w; w_height = h; //load images and set rects background = format_surface("background.jpg"); person = format_surface("person.png"); background_rect_left = background->clip_rect; background_rect_right = background->clip_rect; current_background_piece = 1; //we are displaying the first clip rect_in_view = &background_rect_right; other_rect = &background_rect_left; person_rect = person->clip_rect; background_rect_left.x = 0; background_rect_left.y = 0; background_rect_right.x = background->w; background_rect_right.y = 0; person_rect.y = background_rect_left.h - person_rect.h; person_rect.x = 0; } and here's the move method which is probably causing all the trouble: void Game::move(SDLKey direction) { if(direction == SDLK_RIGHT) { if(move_screen(direction)) { if(!background_reached_right()) { //move background right background_rect_left.x += movement_increment; background_rect_right.x += movement_increment; if(rect_in_view->x >= 0) { //move the other rect in to fill the empty space SDL_Rect* temp; other_rect->x = -w_width + rect_in_view->x; temp = rect_in_view; rect_in_view = other_rect; other_rect = temp; current_background_piece++; std::cout << current_background_piece << std::endl; } if(background_overshoots_right()) { //sees if this next blit is past the surface //this is used only for re-aligning the rects when //the end of the screen is reached background_rect_left.x = 0; background_rect_right.x = w_width; } } } else { //move the person instead person_rect.x += movement_increment; if(get_person_right_side() > w_width) { //person went too far right person_rect.x = w_width - person_rect.w; } } } else if(direction == SDLK_LEFT) { if(move_screen(direction)) { if(!background_reached_left()) { //moves background left background_rect_left.x -= movement_increment; background_rect_right.x -= movement_increment; if(rect_in_view->x <= -w_width) { //swap the rect in view SDL_Rect* temp; rect_in_view->x = w_width; temp = rect_in_view; rect_in_view = other_rect; other_rect = temp; current_background_piece--; std::cout << current_background_piece << std::endl; } if(background_overshoots_left()) { background_rect_left.x = 0; background_rect_right.x = w_width; } } } else { //move the person instead person_rect.x -= movement_increment; if(person_rect.x < 0) { //person went too far left person_rect.x = 0; } } } } without the rest of the code this doesn't make too much sense. Since there is too much of it I'll upload it here for testing. Anyway does anyone know how I could fix this inconsistency?

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  • Memcache key generation strategy

    - by Maxim Veksler
    Given function f1 which receives n String arguments, would be considered better random key generation strategy for memcache for the scenario described below ? Our Memcache client does internal md5sum hashing on the keys it gets public class MemcacheClient { public Object get(String key) { String md5 = Md5sum.md5(key) // Talk to memcached to get the Serialization... return memcached(md5); } } First option public static String f1(String s1, String s2, String s3, String s4) { String key = s1 + s2 + s3 + s4; return get(key); } Second option /** * Calculate hash from Strings * * @param objects vararg list of String's * * @return calculated md5sum hash */ public static String stringHash(Object... strings) { if(strings == null) throw new NullPointerException("D'oh! Can't calculate hash for null"); MD5 md5sum = new MD5(); // if(prevHash != null) // md5sum.Update(prevHash); for(int i = 0; i < strings.length; i++) { if(strings[i] != null) { md5sum.Update("_" + strings[i] + "_"); // Convert to String... } else { // If object is null, allow minimum entropy by hashing it's position md5sum.Update("_" + i + "_"); } } return md5sum.asHex(); } public static String f1(String s1, String s2, String s3, String s4) { String key = stringHash(s1, s2, s3, s4); return get(key); } Note that the possible problem with the second option is that we are doing second md5sum (in the memcache client) on an already md5sum'ed digest result. Thanks for reading, Maxim.

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  • UnitOfWork & StrcutureMap & Desktop Application

    - by Afshin Gh
    When developing Web App and using StrcutureMap i normally use HybridHttpOrThreadLocalScoped for my UnitOfWork Part. (unit of work starts up per web request and ...) What about a desktop app(windows service, console, ...)? There is no session and request in a desktop app. How should i manage UoW in this situation? any good reference or article? I don't want to make it singleton. What should I do?

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  • Tooltips with infinite timeout?

    - by romkyns
    I'm thinking of setting the timeout on all my tooltips in a WinForms application to infinity (or an extremely large value). The motivation is that it's annoying for the user if the tooltip disappears while I'm still reading it, without providing any extra value whatsoever as far as I can tell. Normally I wouldn't ask something like this on StackOverflow, but the overwhelming majority of all software sets timeouts on tooltips, so it makes me wonder whether perhaps there is some important consideration I'm missing? Or is this just an old convention that nobody gives further thought to? If you would hate infinite timeout as opposed to a short timeout, please explain why. (If you just think tooltips are a bad idea altogether then that's a separate consideration; this question is specifically about the infinite timeout.)

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  • Constructing human readable sentences based on a survey

    - by Joshua
    The following is a survey given to course attendees to assess an instructor at the end of the course. Communication Skills 1. The instructor communicated course material clearly and accurately. Yes No 2. The instructor explained course objectives and learning outcomes. Yes No 3. In the event of not understanding course materials the instructor was available outside of class. Yes No 4. Was instructor feedback and grading process clear and helpful? Yes No 5. Do you feel that your oral and written skills have improved while in this course? Yes No We would like to summarize each attendees selection based on the choices chosen by him. If the provided answers were [No, No, Yes, Yes, Yes]. Then we would summarize this as "The instructor was not able to summarize course objectives and learning outcomes clearly, but was available for usually helpful outside of class. The instructor feedback and grading process was clear and helpful and I feel that my oral and written skills have improved because of this course. Based on the selections chosen by the attendee the summary would be quite different. This leads to many answers based on the choices selected and the number of such questions in the survey. The questions are usually provided by the training organization. How do you come up with a generic solution so that this can be effectively translated into a human readable form. I am looking for tools or libraries (java based), suggestions which will help me create such human readable output. I would like to hide the complexity from the end users as much as possible.

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  • Objective-C Simple Inheritance and OO Principles

    - by bleeckerj
    I have a subclass SubClass that inherits from baseclass BaseClass. BaseClass has an initializer, like so: -(id)init { self = [super init]; if(self) { [self commonInit]; } return self; } -(void)commonInit { self.goodStuff = [[NSMutableArray alloc]init]; } SubClass does its initializer, like so: -(id)init { self = [super init]; if(self) { [self commonInit]; } return self; } -(void)commonInit { self.extraGoodStuff = [[NSMutableArray alloc]init]; } Now, I've *never taken a proper Objective-C course, but I'm a programmer more from the Electrical Engineering side, so I make do. I've developed server-side applications mostly in Java though, so I may be seeing the OO world through Java principles. When SubClass is initialized, it calls the BaseClass init and my expectation would be — because inheritance to me implies that characteristics of a BaseClass pass through to SubClass — that the commonInit method in BaseClass would be called during BaseClass init. It is not. I can *sorta understand maybe-possibly-stretch-my-imagination why it wouldn't be. But, then — why wouldn't it be based on the principles of OOP? What does "self" represent if not the instance of the class of the running code? Okay, so — I'm not going to argue that what a well-developed edition of Objective-C is doing is wrong. So, then — what is the pattern I should be using in this case? I want SubClass to have two main bits — the goodStuff that BaseClass has as well as the extraGoodStuff that it deserves as well. Clearly, I've been using the wrong pattern in this type of situation. Am I meant to expose commonInit (which makes me wonder about encapsulation principles — why expose something that, in the Java world at least, would be considered "protected" and something that should only ever be called once for each instance)? I've run into a similar problem in the recent past and tried to muddle through it, but now — I'm really wondering if I've got my principles and concepts all straight in my head. Little help, please.

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  • GRAPH PROBLEM: find an algorithm to determine the shortest path from one point to another in a recta

    - by newba
    I'm getting such an headache trying to elaborate an appropriate algorithm to go from a START position to a EXIT position in a maze. For what is worth, the maze is rectangular, maxsize 500x500 and, in theory, is resolvable by DFS with some branch and bound techniques ... 10 3 4 7 6 3 3 1 2 2 1 0 2 2 2 4 2 2 5 2 2 1 3 0 2 2 2 2 1 3 3 4 2 3 4 4 3 1 1 3 1 2 2 4 2 2 1 Output: 5 1 4 2 Explanation: Our agent looses energy every time he gives a step and he can only move UP, DOWN, LEFT and RIGHT. Also, if the agent arrives with a remaining energy of zero or less, he dies, so we print something like "Impossible". So, in the input 10 is the initial agent's energy, 3 4 is the START position (i.e. column 3, line 4) and we have a maze 7x6. Think this as a kind of labyrinth, in which I want to find the exit that gives the agent a better remaining energy (shortest path). In case there are paths which lead to the same remaining energy, we choose the one which has the small number of steps, of course. I need to know if a DFS to a maze 500x500 in the worst case is feasible with these limitations and how to do it, storing the remaining energy in each step and the number of steps taken so far. The output means the agent arrived with remaining energy= 5 to the exit pos 1 4 in 2 steps. If we look carefully, in this maze it's also possible to exit at pos 3 1 (column 3, row 1) with the same energy but with 3 steps, so we choose the better one. With these in mind, can someone help me some code or pseudo-code? I have troubles working this around with a 2D array and how to store the remaining energy, the path (or number of steps taken)....

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  • Aren't Information Expert / Tell Don't Ask at odds with Single Responsibility Principle?

    - by moffdub
    It is probably just me, which is why I'm asking the question. Information Expert, Tell Don't Ask, and SRP are often mentioned together as best practices. But I think they are at odds. Here is what I'm talking about: Code that favors SRP but violates Tell Don't Ask, Info Expert: Customer bob = ...; // TransferObjectFactory has to use Customer's accessors to do its work, // violates Tell Don't Ask CustomerDTO dto = TransferObjectFactory.createFrom(bob); Code that favors Tell Don't Ask / Info Expert but violates SRP: Customer bob = ...; // Now Customer is doing more than just representing the domain concept of Customer, // violates SRP CustomerDTO dto = bob.toDTO(); If they are indeed at odds, that's a vindication of my OCD. Otherwise, please fill me in on how these practices can co-exist peacefully. Thank you. Edit: someone wants a definition of the terms - Information Expert: objects that have the data needed for the operation should host the operation Tell Don't Ask: don't ask objects for data in order to do work; tell the objects to do the work Single Responsibility Principle: each object should have a narrowly defined responsibility

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  • Circular Dependency Solution

    - by gfoley
    Our current project has ran into a circular dependency issue. Our business logic assembly is using classes and static methods from our SharedLibrary assembly. The SharedLibrary contains a whole bunch of helper functions, such as a SQL Reader class, Enumerators, Global Variables, Error Handling, Logging and Validation. The SharedLibrary needs access to the Business objects, but the Business objects need access to SharedLibrary. The old developers solved this obvious code smell by replicating the functionality of the business objects in the shared library (very anti-DRY). I've spent a day now trying to read about my options to solve this but i'm hitting a dead end. I'm open to the idea of architecture redesign, but only as a last resort. So how can i have a Shared Helper Library which can access the business objects, with the business objects still accessing the Shared Helper Library?

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  • Codechef practice question help needed - find trailing zeros in a factorial

    - by manugupt1
    I have been working on this for 24 hours now, trying to optimize it. The question is how to find the number of trailing zeroes in factorial of a number in range of 10000000 and 10 million test cases in about 8 secs. The code is as follows: #include<iostream> using namespace std; int count5(int a){ int b=0; for(int i=a;i>0;i=i/5){ if(i%15625==0){ b=b+6; i=i/15625; } if(i%3125==0){ b=b+5; i=i/3125; } if(i%625==0){ b=b+4; i=i/625; } if(i%125==0){ b=b+3; i=i/125; } if(i%25==0){ b=b+2; i=i/25; } if(i%5==0){ b++; } else break; } return b; } int main(){ int l; int n=0; cin>>l; //no of test cases taken as input int *T = new int[l]; for(int i=0;i<l;i++) cin>>T[i]; //nos taken as input for the same no of test cases for(int i=0;i<l;i++){ n=0; for(int j=5;j<=T[i];j=j+5){ n+=count5(j); //no of trailing zeroes calculted } cout<<n<<endl; //no for each trialing zero printed } delete []T; } Please help me by suggesting a new approach, or suggesting some modifications to this one.

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  • How to Manage project in this scenario

    - by vijay.shad
    Hi All, I am working on a web application which has got good amount of static or pre-login pages. These pages can have some simple forms as well where we would like to capture the visitor's details. Post login, I have got my main application. I am confused about the development and deployment architecture of my application. Post login part of my application has a release cycle of 1-2 months while pre-login pages are to be updated on a weekly basis. It is difficult to make a release of pre-login pages as the overall war also contains post-login application & which sometimes is not release ready. Currently, I have got both these parts bundled in the single war project. Please help me by letting me know the best practices whereby I can achieve following: Manage the releases of these two parts independently. I am using Maven. So is there a way I can share the resources, such as CSS, images etc between these two parts. Header and footer of my application is going to be same on pre-login & post-login pages. I was thinking of deploying these apps as two war files in my tomcat container. But then how will I manage the common resources like Css, images etc. Rgds Vijay

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  • Perl vs Python: implementation of algorithms to deal with advanced data structures

    - by user350571
    I'm learning perl and everytime I search for perl stuff in the internet I get some random page with people saying that perl should die because code written in it looks like a lesson in steganography. Then they say that python is clean and stuff like that. Now, I know that those comparisons are always stupid and made by fellows that feel that languages are a extension of their boring personality so, let me ask instead: can you give me the implementation of a widely known algorithm to deal with a data structure like red-black trees in both languages so I can compare?

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  • O(log n) algorithm for computing rank of union of two sorted lists?

    - by Eternal Learner
    Given two sorted lists, each containing n real numbers, is there a O(log?n) time algorithm to compute the element of rank i (where i coresponds to index in increasing order) in the union of the two lists, assuming the elements of the two lists are distinct? I can think of using a Merge procedure to merge the 2 lists and then find the A[i] element in constant time. But the Merge would take O(n) time. How do we solve it in O(log n) time?

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  • Are Multiple Iterators possible in php?

    - by artvolk
    Good day! I know that C# allows multiple iterators using yield, like described here: http://stackoverflow.com/questions/1754041/is-multiple-iterators-is-possible-in-c In PHP there is and Iterator interface. Is it possible to implement more than one iteration scenario for a class? More details (EDIT): For example I have class TreeNode implementing single tree node. The whole tree can be expressed using only one this class. I want to provide iterators for iterating all direct and indirect children of current node, for example using BreadthFirst or DepthFirst order. I can implement this Iterators as separate classes but doing so I need that tree node should expose it's children collection as public. C# pseudocode: public class TreeNode<T> { ... public IEnumerable<T> DepthFirstEnumerator { get { // Some tree traversal using 'yield return' } } public IEnumerable<T> BreadthFirstEnumerator { get { // Some tree traversal using 'yield return' } } }

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  • CSS and Page Size and Horizontal Scrollbar

    - by Steve
    When I added some CSS stuff to my page, the page got wider and and horizontal appeared even the content is very minimal and does not require to scroll. How can I remove it. I used the following to remove it but it appears as a hack and I am just playing around with CSS, so is there a proper way to do this

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