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  • How do functional programming languages work?

    - by eSKay
    I was just reading this excellent post, and got some better understanding of what exactly object oriented programming is, how Java implements it in one extreme manner, and how functional programming languages are a contrast. What I was thinking is this: if functional programming languages cannot save any state, how do they do some simple stuff like reading input from a user (I mean how do they "store" it), or storing any data for that matter? For example - how would this simple C thing translate to any functional programming language, for example haskell? #include<stdio.h> int main() { int no; scanf("%d",&no); return 0; }

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  • When writing a game, should you make objects/enemies/etc. have unique ID numbers?

    - by SLC
    I have recently encountered some issues with merely passing references to objects/enemies in a game I am making, and am wondering if I am using the wrong approach. The main issue I have is disposing of enemies and objects, when other enemies or players may still have links to them. For example, if you have a Rabbit, and a Wolf, the Wolf may have selected the Rabbit to be its target. What I am doing, is the wolf has a GameObject Target = null; and when it decides it is hungry, the Target becomes the Rabbit. If the Rabbit then dies, such as another wolf killing it, it cannot be removed from the game properly because this wolf still has a reference to it. In addition, if you are using a decoupled approach, the rabbit could hit by lightning, reducing its health to below zero. When it next updates itself, it realises it has died, and is removed from the game... but there is no way to update everything that is interested in it. If you gave every enemy a unique ID, you could simply use references to that instead, and use a central lookup class that handled it. If the monster died, the lookup class could remove it from its own index, and subsequently anything trying to access it would be informed that it's dead, and then they could act accordingly. Any thoughts on this?

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  • mysql unique-constraint

    - by Cypher
    I have two tables -- Variables (id, name) and Variable_Entries (id, var_id, value). I want each variable to have a unique set of entries. If I make the value entry unique then a different variable won't be able to have that same value which is not right. Is there some way to make the value column unique for identical var_id's?

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  • Best method to store Enum in Database

    - by LnDCobra
    What is the best method of storing an Enum in a Database using C# And Visual Studio and MySQL Data Connector. I am going to be creating a new project with over 100 Enums, and majority of them will have to be stored in the database. Creating converters for each one would be a long winded process therefore I'm wondering if visual studio or someone has any methods for this that I haven't heard off.

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  • Reuse nib's across multiple UIViewControllers

    - by colm
    I've created some custom UITableViewCells in a nib file and would like to use that across multiple UIViewControllers. Can anyone tell me the best practice way to do that? My limited knowledge around loading nibs seems to suggest that you have to specify a single owner class in Interface Builder. Thanks.

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  • How to structure a Genetic Algorithm class hierarchy?

    - by MahlerFive
    I'm doing some work with Genetic Algorithms and want to write my own GA classes. Since a GA can have different ways of doing selection, mutation, cross-over, generating an initial population, calculating fitness, and terminating the algorithm, I need a way to plug in different combinations of these. My initial approach was to have an abstract class that had all of these methods defined as pure virtual, and any concrete class would have to implement them. If I want to try out two GAs that are the same but with different cross-over methods for example, I would have to make an abstract class that inherits from GeneticAlgorithm and implements all the methods except the cross-over method, then two concrete classes that inherit from this class and only implement the cross-over method. The downside to this is that every time I want to swap out a method or two to try out something new I have to make one or more new classes. Is there another approach that might apply better to this problem?

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  • Proper way to set class variables

    - by ensnare
    I'm writing a class to insert users into a database, and before I get too far in, I just want to make sure that my OO approach is clean: class User(object): def setName(self,name): #Do sanity checks on name self._name = name def setPassword(self,password): #Check password length > 6 characters #Encrypt to md5 self._password = password def commit(self): #Commit to database >>u = User() >>u.setName('Jason Martinez') >>u.setPassword('linebreak') >>u.commit() Is this the right approach? Should I declare class variables up top? Should I use a _ in front of all the class variables to make them private? Thanks for helping out.

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  • Best pattern for storing (product) attributes in SQL Server

    - by EdH
    We are starting a new project where we need to store product and many product attributes in a database. The technology stack is MS SQL 2008 and Entity Framework 4.0 / LINQ for data access. The products (and Products Table) are pretty straightforward (a SKU, manufacturer, price, etc..). However there are also many attributes to store with each product (think industrial widgets). These may range from color to certification(s) to pipe size. Every product may have different attributes, and some may have multiples of the same attribute (Ex: Certifications). The current proposal is that we will basically have a name/value pair table with a FK back to the product ID in each row. An example of the attributes Table may look like this: ProdID AttributeName AttributeValue 123 Color Blue 123 FittingSize 1.25 123 Certification AS1111 123 Certification EE2212 123 Certification FM.3 456 Pipe 11 678 Color Red 999 Certification AE1111 ... Note: Attribute name would likely come from a lookup table or enum. So the main question here is: Is this the best pattern for doing something like this? How will the performance be? Queries will be based on a JOIN of the product and attributes table, and generally need many WHEREs to filter on specific attributes - the most common search will be to find a product based on a set of known/desired attributes. If anyone has any suggestions or a better pattern for this type of data, please let me know. Thanks! -Ed

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  • database splitting; multiple tables

    - by Ben
    I am coding a classifieds ad web app. What is the optimal way to structure the database for this? Because of the high repeatability, would it be faster (in terms of searching/indexing) to have a separate table in the database for each city? Or would it be okay to just have one table for every city (it would have a lot of rows..). The classifieds table has id, user_id, city_name, category,[description and detail fields].

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  • MVC implementation/best-practices question

    - by Vivin Paliath
    I have to work with some code that isn't truly MVC (i.e., it doesn't use an explicit framework among other things). Right now we make do with servlets that pass data to services. Here is my problem. I am receiving a post to a servlet that contains a whole bunch of address data that I have to save to the database. The data is (obviously) in the HttpRequest object. My question is, how do I pass this data into a service? I am reluctant to do it like this: AddressService.saveAddress(request); Because I don't think the service should have a dependency on the request. My other option is to do something like this: String addressLine = request.getParameter("addressLine"); .. .. about 7 other parameters .. String zip = request.getParameter("zip"); AddressService.saveAddress(addressLine, ... 7 other parameters ..., zip); But I don't like having a function with a huge number of parameters either. I was thinking of making an intermediate object called AddressData that would hold data from the request, and then passing that into the service. Is that an acceptable way of doing things?

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  • Suggest a Game Idea for my 3D World

    - by mrlinx
    Been creating a 3D complete world in OpenGL. For now, it features navigation like Google Earth, making possible the zooming from outter space to meter like level. My question is: How do you suggest I make this a fun and interesting game? My initial tought was to have a kind of moon lander where the user simply navigated the lander around the world. Anything better to suggest?

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  • Daylight saving time - do and don'ts

    - by Oded
    I am hoping to make this question and the answers to it the definitive guide to dealing with daylight saving time, in particular for dealing with the actual change overs. Many systems are dependent on keeping accurate time, the problem is with changes to time due to daylight savings - moving the clock forward or backwards. For instance, one has business rules in an order taking system that depend on the time of the order - if the clock changes, the rules might not be as clear. How should the time of the order be persisted? There is of course an endless number of scenarios - this one is simply an illustrative one. How have you dealt with the daylight saving issue? What assumptions are part of your solution? (looking for context here) As important, if not more so: What did you try that did not work? Why did it not work? I would be interested in programming, OS, data persistence and other pertinent aspects of the issue. General answers are great, but I would also like to see details especially if they are only available on one platform.

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  • algorithm diagram

    - by tunl
    This is the max searching algorithm diagram: So, I wonder how can draw diagram for Recursion in HaNoi Tower program: package tunl; public class TowersApp { static int n = 3; public static void main(String[] args) { TowersApp.doTowers(3, 'A', 'B', 'C'); } public static void doTowers(int n, char from, char inter, char to) { if (n == 1) { System.out.println("disk 1 from "+ from + " to " + to); } else { doTowers(n-1, from, to, inter); System.out.println("disk " + n + " from " + from + " to " + to); doTowers(n-1, inter, from, to); } } } I can't draw it. Anyone can help me !!!

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  • What makes MVVM uniquely suited to WPF?

    - by Reed Copsey
    The Model-View-ViewModel is very popular with WPF and Silverlight. I've been using this for my most recent projects, and am a very large fan. I understand that it's a refinement of MVP. However, I am wondering exactly what unique characteristics of WPF (and Silverlight) allow MVVM to work, and prevent (or at least make difficult) this pattern from working using other frameworks or technologies. I know MVVM has a strong dependency on the powerful data binding technology within WPF. This is the one feature which many articles and blogs seem to mention as being the key to WPF providing the means of the strong separation of View from ViewModel. However, data binding exists in many forms in other UI frameworks. There are even projects like Truss that provide WPF-style databinding to POCO in .NET. What features, other than data binding, make WPF and Silverlight uniquely suited to Model-View-ViewModel?

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  • How to add an "Export to ebook" feature to a site?

    - by systempuntoout
    How could i add to a blog or site in general a feature that let users export the content to epub format or some other open ebook formats? It's not a feature that i normally see on most of the site i browse every day (some has export to pdf that is not great as ebook format), do you think it is feasible? I own an ebook reader and reading saved html to pdf pages is not so good. I'm searching for a general solution here so i have not specified any specific technology; if you have some sites that offer this feature i would like to try them. thanks

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  • Save data in bulk.

    - by Muhammad Kashif Nadeem
    I have a window having multiple tabs. Each tab having different grids. I want to save all changes on any tab on any grid in bulk. I mean I have one save button which will save all changes in any grid on any tab. I think DataTables will work fine here. Can you suggest me that it is good to use DataTables to ADD/Edit data and save data in bulk using these DataTables OR is there any better way to achieve this. My DAL is generated from LLBLGen Pro (ORM) but you are open to suggest me a solution. Thanks. Edit: I am using Telerik controls so I can get all data in DataTable like DataTable dtProducts = this.radGridView1.DataSource as DataTable;

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  • 3rd party data - Store in Data Warehouse or Primary database?

    - by brydgesk
    This is mostly a data warehouse philosophy question. My project involves an Oracle forms application, and a Teradata Data Warehouse for reporting and ad-hoc purposes. In addition to the primary data created by the users of our application, we also require data from various other sources. Currently, this 3rd party data comes via FTPd flat files directly to our Data Warehouse. To access the data, our users must use a series of custom BusinessObjects reports. My question is, would it make more sense for this data to be sent to our source Oracle system instead? Is it ever appropriate for a Data Warehouse to be the point of origin for users to access raw data? In short, is it more important that the operational database contain only the data created by your project, or that the data warehouse remain dedicated solely to reporting and analysis?

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  • MVC pattern and (Game) State pattern

    - by topright
    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 classes, not 1). What are practical ways of combining these 2 concepts?

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  • SQL Server: pulling and updating local data

    - by SDReyes
    Hi guys, I have two SQL Server 2008 databases called Anna and Bob. Bob has to pull and transform data from Anna to keep updated his tables. Ideally Bob will be always synchronized with Anna, but some delay would be acceptable. What is the best way to do this? Thanks in advance.

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  • Advice on displaying and allowing editing of data using ASP.NET MVC?

    - by Remnant
    I am embarking upon my first ASP.NET MVC project and I would like to get some input on possible ways to display database data and general best practice. In short, the body of my webpage will show data from my database in a table like format, with each table row showing similar data. For example: Name Age Position Date Joined Jon Smith 23 Striker 18th Mar 2005 John Doe 38 Defender 3rd Jan 1988 In terms of functionality, primarily I’d like to give the user the ability to edit the data and, after the edit, commit the edit to the database and refresh the view.The reason I want to refresh the view is because the data is date ordered and I will need to re-sort if the user edits a date field. My main question is what architecture / tools would be best suited to this fulfil my requirements at a high level? From the research I have done so far my initial conclusions were: ADO.NET for data retrieval. This is something I have used before and feel comfortable with. I like the look of LINQ to SQL but don’t want to make the learning curve any steeper for my first outing into MVC land just yet. Partial Views to create a template and then iterate through a datatable that I have pulled back from my database model. jQuery to allow the user to edit data in the table, error check edited data entries etc. Also, my intial view was that caching the data would not be a key requirement here. The only field a user will be able to update is the field and, if they do, I will need to commit that data to the database immediately and then refresh the view (as the data is date sorted). Any thoughts on this? Alternatively, I have seen some jQuery plug-ins that emulate a datagrid and provide associated functionality. My first thoughts are that I do not need all the functionality that comes with these plug-ins (e.g. zebra striping, ability to sort by column using sort glyph in column headers etc .) and I don’t really see any benefit to this over and above the solution I have outlined above. Again, is there reason to reconsider this view? Finally, when a user edits a date , I will need to refresh the view. In order to do this I had been reading about Html.RenderAction and this seemed like it may be a better option than using Partial Views as I can incorporate application logic into the action method. Am I right to consider Html.RenderAction or have I misunderstood its usage? Hope this post is clear and not too long. I did consider separate posts for each topic (e.g. Partial View vs. Html.RenderAction, when to use jQury datagrid plug-in) but it feels like these issues are so intertwined that they need to be dealt with in contect of each other. Thanks

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  • Are web-safe colors still relevant?

    - by Gavin Miller
    Since the vast majority of monitors are 16-bit color or more, including mobile devices, does it make sense to even consider web-safe colors when choosing color schemes? Or is it something that ought to be relegated to history as a piece of trivia? For those of you that don't know what web-safe colors are: Another set of 216 color values is commonly considered to be the "web-safe" color palette, developed at a time when many computer displays were only capable of displaying 256 colors. A set of colors was needed that could be shown without dithering on 256-color displays; the number 216 was chosen partly because computer operating systems customarily reserved sixteen to twenty colors for their own use; it was also selected because it allows exactly six shades each of red, green, and blue (6 × 6 × 6 = 216). The list of colors is often presented as if it has special properties that render them immune to dithering. In fact, on 256-color displays applications can set a palette of any selection of colors that they choose, dithering the rest. These colors were chosen specifically because they matched the palettes selected by the then leading browser applications. [Wikipedia]

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