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• What makes a bad programming language bad?

  - by sub

  We have all seen things like the typing system of JavaScript (There is a funny post including a truth table somewhere around here). I consider this one of the main things that makes a programming language bad. Other things that spring to mind: Bad Error messages (Either obfuscated so you can't figure out whats wrong, not existing or simply too long and red) The language wasn't planned and just grew uncontrolled in all directions (PHP?) The language encourages bad programm(er/ing) habits such as: Global variables everywhere, bad variable names Inconsistent naming conventions inside the language I can't come up with any more at the moment and would be very happy to read what you think about this. What shouldn't be missing in a language created to be as bad (from the perspectives of the programmer, the company that hires to programmer, the team leader and the customer) as possible? (I ask this because I'm designing a bad, experimental language at the moment)

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• Import OLE Object from Access to MySQL

  - by SecretDeveloper

  I have a table in an access table which contains Product entries, one of the columns has a jpg image stored as an OLE Object. I am trying to import this table to MySQL but nothing seems to work. I have tried the MySQL migration tool but that has a known issue with Access and OLE Objects. (The issue being it doesnt work and leaves the fields blank) I also tried the suggestion on this site and while the data is imported it seems as though the image is getting corrupted in the transfer. When i try to preview the image i just get a binary view, if i save it on disk as a jpg image and try to open it i get an error stating the image is corrupt. The images in Access are fine and can be previewed. Access is storing the data as an OLE Object and when i import it to MySql it is saved in a MediumBlob field. Has anyone had this issue before and how did they resolve it ?

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• Proper reconstitution of Aggregate objects in the Repository?

  - by Jebb

  Assuming that no ORM (e.g. Doctrine) is used inside the Repository, my question is what is the proper way of instantiating the Aggregate objects? Is it instantiating the child objects directly inside the Repository and just assign it to the Aggregate Root through its setters or the Aggregate Root is responsible of constructing its child entities/objects? Example 1: class UserRepository { // Create user domain entity. $user = new User(); $user->setName('Juan'); // Create child object orders entity. $orders = new Orders($orders); $user->setOrders($orders); } Example 2: class UserRepository { // Create user domain entity. $user = new User(); $user->setName('Juan'); // Get orders. $orders = $ordersDao->findByUser(1); $user->setOrders($orders); } whereas in example 2, instantiation of orders are taken care inside the user entity.

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• Code organization in an FP application

  - by fig-gnuton

  What are common or recommended ways to organize an application written in a functional language? Along what lines would you decide to create separate files, modules, directories, etc.?

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• curl function and multipart/form-data issue

  - by hd

  does curl function need any special option to post multipart/form-data ?

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• how to aviod infinite loop in observer pattern?

  - by joseph

  Hello. I have only one class with many instances. Every instance is observer of couple of other instances. As well every instance can be observable by couple of another instances. How to avoid infinite loop of calling update() in observers?

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• RestKit : Not able to perform mapping using coredata

  - by Ashish Beuwria

  I'm using rest kit 0.20.3 and Xcode 5. Without core data I'm able to perform all rest kit operation, but when I've tried it with core data, I'm not even able to perform GET due to some problem. I can't figure it out. I'm new with core data. So pls help. Here is my code: AppDelegate.m @implementation CardGameAppDelegate @synthesize managedObjectContext = _managedObjectContext; @synthesize managedObjectModel = _managedObjectModel; @synthesize persistentStoreCoordinator = _persistentStoreCoordinator; - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { RKLogConfigureByName("RestKit", RKLogLevelWarning); RKLogConfigureByName("RestKit/ObjectMapping", RKLogLevelTrace); RKLogConfigureByName("RestKit/Network", RKLogLevelTrace); RKObjectManager *objectManager = [RKObjectManager managerWithBaseURL:[NSURL URLWithString:@"http://192.168.1.3:3010/"]]; RKManagedObjectStore *objectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:self.managedObjectModel]; objectManager.managedObjectStore = objectStore; RKEntityMapping *playerMapping = [RKEntityMapping mappingForEntityForName:@"Player" inManagedObjectStore:objectStore]; [playerMapping addAttributeMappingsFromDictionary:@{@"id": @"playerId", @"name": @"playerName", @"age" : @"playerAge", @"created_at": @"createdAt", @"updated_at": @"updatedAt"}]; RKResponseDescriptor *responseDesc = [RKResponseDescriptor responseDescriptorWithMapping:playerMapping method:RKRequestMethodGET pathPattern:@"/players.json" keyPath:nil statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)]; [objectManager addResponseDescriptor:responseDesc]; PlayersTableViewController *ptvc = (PlayersTableViewController *)self.window.rootViewController; ptvc.managedObjectContext = self.managedObjectContext; return YES; } and code for playerTableViewController.h #import <UIKit/UIKit.h> @interface PlayersTableViewController : UITableViewController <NSFetchedResultsControllerDelegate> @property (strong, nonatomic) NSFetchedResultsController *fetchedResultsController; @property (strong, nonatomic) NSManagedObjectContext *managedObjectContext; @end and PlayerTableViewController.m get method: -(void)loadPlayers{ [[RKObjectManager sharedManager] getObjectsAtPath:@"/players.json" parameters:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult){ [self.refreshControl endRefreshing]; } failure:^(RKObjectRequestOperation *operation, NSError *error) { [self.refreshControl endRefreshing]; UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"An Error Has Occurred" message:[error localizedDescription] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alertView show]; }]; } I'm getting the following error : Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Unable to perform mapping: No `managedObjectContext` assigned. (Mapping response.URL = http://192.168.1.3:3010/players.json)'

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• How you would you describe the Observer pattern in beginner language?

  - by Sheldon

  Currently, my level of understanding is below all the coding examples on the web about the Observer Pattern. I understand it simply as being almost a subscription that updates all other events when a change is made that the delegate registers. However, I'm very unstable in my true comprehension of the benefits and uses. I've done some googling, but most are above my level of understanding. I'm trying to implement this pattern with my current homework assignment, and to truly make sense on my project need a better understanding of the pattern itself and perhaps an example to see what its use. I don't want to force this pattern into something just to submit, I need to understand the purpose and develop my methods accordingly so that it actually serves a good purpose. My text doesn't really go into it, just mentions it in one sentence. MSDN was hard for me to understand, as I'm a beginner on this, and it seems more of an advanced topic. How would you describe this Observer pattern and its uses in C# to a beginner? For an example, please keep code very simple so I can understand the purpose more than complex code snippets. I'm trying to use it effectively with some simple textbox string manipulations and using delegates for my assignment, so a pointer would help!

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• WPF Data virtualizing ListView

  - by Robert Jeppesen

  In our current WinForms app, we are displaying millions of records in ListView, using virtualization. Rows are loaded from DB as they are requested. This works well, with good performance. This is a showstopper for migrating to WPF for us. We need data virtualization in a ListView, like WinForms 2.0 has. Do you know a decent third-party control, or a relatively easy way of doing it with built-in controls? It doesn't need to be a DataGrid, a simple ListView will suffice. Note, I'm note talking about UI virtualization, it's data virtualization.

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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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• Hibernate : Opinions in Composite PK vs Surrogate PK

  - by Albert Kam

  As i understand it, whenever i use @Id and @GeneratedValue on a Long field inside JPA/Hibernate entity, i'm actually using a surrogate key, and i think this is a very nice way to define a primary key considering my not-so-good experiences in using composite primary keys, where : there are more than 1 business-value-columns combination that become a unique PK the composite pk values get duplicated across the table details cannot change the business value inside that composite PK I know hibernate can support both types of PK, but im left wondering by my previous chats with experienced colleagues where they said that composite PK is easier to deal with when doing complex SQL queries and stored procedure processes. They went on saying that when using surrogate keys will complicate things when doing joining and there are several condition when it's impossible to do some stuffs when using surrogate keys. Although im sorry i cant explain the detail here since i was not clear enough when they explain it. Maybe i'll put more details next time. Im currently trying to do a project, and want to try out surrogate keys, since it's not getting duplicated across tables, and we can change the business-column values. And when the need for some business value combination uniqueness, i can use something like : @Table(name="MY_TABLE", uniqueConstraints={ @UniqueConstraint(columnNames={"FIRST_NAME", "LAST_NAME"}) // name + lastName combination must be unique But im still in doubt because of the previous discussion about the composite key. Could you share your experiences in this matter ? Thank you !

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• where to enlist transaction with parent child delete (repository or bll)?

  - by Caroline Showden

  My app uses a business layer which calls a repository which uses linq to sql. I have an Item class that has an enum type property and an ItemDetail property. I need to implement a delete method that: (1) always delete the Item (2) if the item.type is XYZ and the ItemDetail is not null, delete the ItemDetail as well. My question is where should this logic be housed? If I have it in my business logic which I would prefer, this involves two separate repository calls, each of which uses a separate datacontext. I would have to wrap both calls is a System.Transaction which (in sql 2005) get promoted to a distributed transaction which is not ideal. I can move it all to a single repository call and the transaction will be handled implicitly by the datacontext but feel that this is really business logic so does not belong in the repository. Thoughts? Carrie

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• R and SPSS difference

  - by sfactor

  i will be analysing vast amount of network traffic related data shortly. i will pre-process the data in order to analyse it. i have found that R and SPSS are among the most popular tools for statistical analysis. i will also be generating quite a lot of graphs and charts. so i was wondering what is the basic difference between these two softwares. i am not asking which one is better. i just wanted to know what are the difference in terms of workflow between the two besides the fact that SPSS has a GUI. I will be mostly working with scripts in either case anyway so i wanted to know about the other differences.

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• CQRS - The query side

  - by mattcodes

  A lot of the blogsphere articles related to CQRS (command query repsonsibility) seperation seem to imply that all screens/viewmodels are flat. e.g. Name, Age, Location Of Birth etc.. and thus the suggestion that implementation wise we stick them into fast read source etc.. single table per view mySQL etc.. and pull them out with something like primitive SqlDataReader, kick that nasty nhibernate ORM etc.. However, whilst I agree that domain models dont mapped well to most screens, many of the screens that I work with are more dimensional, and Im sure this is pretty common in LOB apps. So my question is how are people handling screen where by for example it displays a summary of customer details and then a list of their orders with a [more detail] link etc.... I thought about keeping with the straight forward SQL query to the Query Database breaking off the outer join so can build a suitable ViewModel to View but it seems like overkill? Alternatively (this is starting to feel yuck) in CustomerSummaryView table have a text/big (whatever the type is in your DB) column called Orders, and the columns for the Order summary screen grid are seperated by , and rows by |. Even with XML datatype it still feeel dirty. Any thoughts on an optimal practice?

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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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• WPF ListView Data Binding wont synchronize

  - by Aviatrix

  my listview will display only the item that its added by the constructor and it wont add the items that i add dynamically public class PostList : ObservableCollection<PostData> { public PostList() : base() { Add(new PostData("Isak", "Dinesen")); // Add(new PostData("Victor", "Hugo")); // Add(new PostData("Jules", "Verne")); } public void AddToList (string[] data){ string username2, msg; msg = data[0]; username2 = data[1]; Add(new PostData(msg, username2)); } } public class PostData { private string Username; private string Msg; private string Avatar; private string LinkAttached; private string PicAttached; private string VideoAttached; public PostData(string msg ,string username, string avatar=null, string link=null,string pic=null ,string video=null) { this.Username = username; this.Msg = msg; this.Avatar = avatar; this.LinkAttached = link; this.PicAttached = pic; this.VideoAttached = video; } public string pMsg { get { return Msg; } set { Msg = value; } } public string pUsername { get { return Username; } set { Username = value; } } ..... ..... } Xaml <ListView x:Name="PostListView" BorderThickness="0" MinHeight="300" Background="{x:Null}" BorderBrush="{x:Null}" Foreground="{x:Null}" VerticalContentAlignment="Top" ScrollViewer.HorizontalScrollBarVisibility="Disabled" ScrollViewer.VerticalScrollBarVisibility="Disabled" IsSynchronizedWithCurrentItem="True" MinWidth="332" SelectedIndex="0" SelectionMode="Extended" AlternationCount="1" ItemsSource="{Binding Source={StaticResource PostListData}}"> <ListView.ItemTemplate> <DataTemplate> <DockPanel x:Name="SinglePost" VerticalAlignment="Top" ScrollViewer.CanContentScroll="True" ClipToBounds="True" Width="333" Height="70" d:LayoutOverrides="VerticalAlignment" d:IsEffectDisabled="True"> <StackPanel x:Name="AvatarNickHolder" Width="60"> <Label x:Name="Nick" HorizontalAlignment="Center" Margin="5,0" VerticalAlignment="Top" Height="15" Content="{Binding Path=pUsername}" FontFamily="Arial" FontSize="10.667" Padding="5,0"/> <Image x:Name="Avatar" HorizontalAlignment="Center" Margin="5,0,5,5" VerticalAlignment="Top" Width="50" Height="50" IsHitTestVisible="False" Source="1045443356IMG_0972.jpg" Stretch="UniformToFill"/> </StackPanel> <TextBlock x:Name="userPostText" Margin="0,0,5,0" VerticalAlignment="Center" FontSize="10.667" Text="{Binding Path=pMsg}" TextWrapping="Wrap"/> </DockPanel> </DataTemplate> </ListView.ItemTemplate> </ListView>

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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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• NDbUnit MySQL Assembly Version Conflict

  - by LnDCobra

  I am trying to use NHiberanate with NDbUnit but I cannot as NDbUnit tried to load MySql.Data version 1.0.10.1 and NHibernate tries to load version 6.2.2.0 and I can only reference one of them. Here is the error I get when i try to run NDbUnit Set Up System.IO.FileLoadException: Could not load file or assembly 'MySql.Data, Version=1.0.10.1, Culture=neutral, PublicKeyToken=c5687fc88969c44d' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) at NDbUnit.Core.MySqlClient.MySqlDbCommandBuilder.GetConnection(String connectionString) at NDbUnit.Core.DbCommandBuilder..ctor(String connectionString) at NDbUnit.Core.MySqlClient.MySqlDbCommandBuilder..ctor(String connectionString) at NDbUnit.Core.MySqlClient.MySqlDbUnitTest.CreateDbCommandBuilder(String connectionString) at NDbUnit.Core.NDbUnitTest.GetDbCommandBuilder() at NDbUnit.Core.NDbUnitTest.ReadXmlSchema(Stream xmlSchema) at NDbUnit.Core.NDbUnitTest.ReadXmlSchema(String xmlSchemaFile) at Proteus.Utility.UnitTest.DatabaseUnitTestBase.SaveDatabase(String connectionString, String schemaFilePathName, String datasetFilePathName, DatabaseClientType clientType) at TGS.UserAccountControlTest.UserAccountManagerTest._TestFixtureSetup() in C:\Documents and Settings\Michal\My Documents\Visual Studio 2008\Projects\TGS\TGS.UserAccountControlTest\UserAccountManagerTest.cs:line 69 Does anyone know how to resolve this?

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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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• Java : Storing Data in Array Of Object from JOptionPane Dialog

  - by Bader

  hi guys i need to know how i can insert data inside objects inside an array of objects using my already made Set methods. i need to know how should i do it through user , i mean JOptionPane input dialog [code] student[] s=new student[5]; for (int i=1 ; i <= s.length ;i++) { s[i] = new student(i,"AAA","Ecommerce",0.0); } for (int i=1; i<=s.length;i++) { name = JOptionPane.showInputDialog("Please Write Name for student n " + i); major = JOptionPane.showInputDialog("Please Write Major for student n " + i); gpa =Double.parseDouble(JOptionPane.showInputDialog("Please Write GPA for student n " +i)); s[i]=new student(i,name,major,gpa); } [/code] i tried to do vars here that get data from user by JOptionPane, but it seems that i only use my already made constructor , not the Set methods. i need to use the methods because it has some validation code inside it. any ideas ?

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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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• 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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• Building a many-to-many db schema using only an unpredictable number of foreign keys

  - by user1449855

  Good afternoon (at least around here), I have a many-to-many relationship schema that I'm having trouble building. The main problem is that I'm only working with primary and foreign keys (no varchars or enums to simplify things) and the number of many-to-many relationships is not predictable and can increase at any time. I looked around at various questions and couldn't find something that directly addressed this issue. I split the problem in half, so I now have two one-to-many schemas. One is solved but the other is giving me fits. Let's assume table FOO is a standard, boring table that has a simple primary key. It's the one in the one-to-many relationship. Table BAR can relate to multiple keys of FOO. The number of related keys is not known beforehand. An example: From a query FOO returns ids 3, 4, 5. BAR needs a unique key that relates to 3, 4, 5 (though there could be any number of ids returned) The usual join table does not work: Table FOO_BAR primary_key | foo_id | bar_id | Since FOO returns 3 unique keys and here bar_id has a one-to-one relationship with foo_id. Having two join tables does not seem to work either, as it still can't map foo_ids 3, 4, 5 to a single bar_id. Table FOO_TO_BAR primary_key | foo_id | bar_to_foo_id | Table BAR_TO_FOO primary_key | foo_to_bar_id | bar_id | What am I doing wrong? Am I making things more complicated than they are? How should I approach the problem? Thanks a lot for the help.

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• Most Astonishing Violation of the Principle of Least Astonishment

  - by Adam Liss

  The Principle of Least Astonishment suggests that a system should operate as a user would expect it to, as much as possible. In other words, it should never "astonish" the user with unexpected behavior. In your experience as the "astonishee," what types of systems are the worst offenders, and if you were the project manager, how would you correct the problem? Bonus if your answer describes how you'd retrain the developers!

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• Shortest Path algorithm of a different kind

  - by Ram Bhat

  Hey guys, Lets say you have a grid like this (made randomly) Now lets say you have a car starting randomly from one of the while boxes, what would be the shortest path to go through each one of the white boxes? you can visit each white box as many times as you want and cant Jump over the black boxes. The black boxes are like walls. In simple words you can move from white box to white box only.. You can move in any direction, even diagonally.

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