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• Generalized plugable caching pattern?

  - by BCS

  Given that it's one of the hard things in computer science, does anyone know of a way to set up a plugable caching strategy? What I'm thinking of would allow me to write a program with minimal thought as to what needs to be cached (e.i. use some sort of boiler-plate, low/no cost pattern that compiles away to nothing anywhere I might want caching) and then when things are further along and I know where I need caching I can add it in without making invasive code changes. As an idea to the kind of solution I'm looking for; I'm working with the D programing language (but halfway sane C++ would be fine) and I like template.

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• What is the best solution to do Reporting on Object data for .NET ?

  - by Peter Fox

  Hi, Our projects are using objects as the data source to reports. Our business layer is returning single objects or IEnumerable. Our reports (quite complex) need to display value-type properties of the object, and its related objects. Typical case would be, from a List, display a master report with category data, then a subreport with data for each Product inside each Category, then a subreport for each Part of each Product, and so on. Reporting from the database is not an option for us. We have tried so far - Reporting Services : works but have to mess around with the XML definition of the report to define the datasource classes, very hard to work with if you use an object datasource, architecturally not too clean - Telerik Reports : quite nice (esp., nice architecture) but seems to have problems with complex reports (master/sub), does not give great paging control, rumored to have performance/crash problems (immature product). Does anyone know a good reporting solution that can be integrated in an ASP.NET application and works well with objects as datasources ?

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• How to do a UITable cell with triangle indicator?

  - by zardon

  In the Linked in iphone application I noticed that they have a tableview, see the following picture with what appears to have a triangle indicator pointing upwards. Notice how the tableview cell has a little triangle pointing upwards and is part of a tableview cell. The triangle is the ---^--- part of the image. I'm wondering. How do you make a UITableView with this triangle indicator, and what is this effect called? Thanks

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• Data Modeling Help - Do I add another table, change existing table's usage, or something else?

  - by StackOverflowNewbie

  Assume I have the following tables and relationships: Person - Id (PK) - Name A Person can have 0 or more pets: Pet - Id (PK) - PersonId (FK) - Name A person can have 0 or more attributes (e.g. age, height, weight): PersonAttribute _ Id (PK) - PersonId (FK) - Name - Value PROBLEM: I need to represent pet attributes, too. As it turns out, these pet attributes are, in most cases, identical to the attributes of a person (e.g. a pet can have an age, height, and weight too). How do I represent pet attributes? Do I create a PetAttribute table? PetAttribute Id (PK) PetId (FK) Name Value Do I change PersonAttribute to GenericAttribute and have 2 foreign keys in it - one connecting to Person, the other connecting to Pet? GenericAttribute Id (PK) PersonId (FK) PetId (FK) Name Value NOTE: if PersonId is set, then PetId is not set. If PetId is set, PersonId is not set. Do something else?

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• Singleton Pattern combine with a Decorator

  - by Mike

  Attached is a classic Decorator pattern. My question is how would you modify the below code so that you can wrap zero or one of each topping on to the Pizza Right now I can have a Pepporini - Sausage -- Pepporini -- Pizza class driving the total cost up to $10, charging twice for Pepporini. I don't think I want to use the Chain of Responsibility pattern as order does not matter and not all toppings are used? Thank you namespace PizzaDecorator { public interface IPizza { double CalculateCost(); } public class Pizza: IPizza { public Pizza() { } public double CalculateCost() { return 8.00; } } public abstract class Topping : IPizza { protected IPizza _pizzaItem; public Topping(IPizza pizzaItem) { this._pizzaItem = pizzaItem; } public abstract double CalculateCost(); } public class Pepporini : Topping { public Pepporini(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + 0.50; } } public class Sausage : Topping { public Sausage(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + 1.00; } } public class Onions : Topping { public Onions(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + .25; } } }

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• What's an easy way to set up object communication in Obj-C?

  - by seaworthy

  I am trying to send a slider value from a controller object to a method of a model object. The later is implemented in the separate file and I have appropriate headers. I think the problem is that I am not sure how to instantiate the receiver in order to produce a working method for the controller. Here is the controller's method. -(IBAction)setValue:(id)slider {[Model setValue:[slider floatValue]];} @implementation Model -(void)setValue:(float)n{ printf("%f",n); } @end What I get is 'Model' may not respond to '+setValue' warning and no output in my console. Any insight is appreciated.

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• Storing n-grams in database in < n number of tables.

  - by kurige

  If I was writing a piece of software that attempted to predict what word a user was going to type next using the two previous words the user had typed, I would create two tables. Like so: == 1-gram table == Token | NextWord | Frequency ------+----------+----------- "I" | "like" | 15 "I" | "hate" | 20 == 2-gram table == Token | NextWord | Frequency ---------+------------+----------- "I like" | "apples" | 8 "I like" | "tomatoes" | 12 "I hate" | "tomatoes" | 20 "I hate" | "apples" | 2 Following this example implimentation the user types "I" and the software, using the above database, predicts that the next word the user is going to type is "hate". If the user does type "hate" then the software will then predict that the next word the user is going to type is "tomatoes". However, this implimentation would require a table for each additional n-gram that I choose to take into account. If I decided that I wanted to take the 5 or 6 preceding words into account when predicting the next word, then I would need 5-6 tables, and an exponentially increase in space per n-gram. What would be the best way to represent this in only one or two tables, that has no upper-limit on the number of n-grams I can support?

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• Drop Shadow Center Column Website web page

  - by hagope

  How can I add a drop shadow effect to a website that has one center column? Some examples of what I mean: lala.com mint.com

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• Tips on designing a .NET API for future use with F#

  - by Drew Noakes

  I'm in the process of designing a .NET API to allow developers to create RoboCup agents for the 3D simulated soccer league. I'm pretty happy with how the API work with C# code, however I would like to use this project to improve my F# skill (which is currently based on reading rather than practice). So I would like to ask what kinds of things I should consider when designing an API that is to be consumed by both C# and F# code. Some points. I make fairly heavy use of matrix and vector math. These are currently immutable classes/structs. The API currently defines a few interfaces with the consumer implements (eg: IAgent), using instances of their implementations (eg: MyAgent) to construct other API classes (eg: new Client(myAgent)). The API fires events. The API exposes a few delegate types. The API includes several enums. I'd like to release a version of the API as soon as possible and don't want to make major changes to it later if I realise it's too difficult to work with from F#. Any advice is appreciated.

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• Which source control paradigm and solution to embed in a custom editor application?

  - by Greg Harman

  I am building an application that manages a number of custom objects, which may be edited concurrently by multiple users (using different instances of the application). These objects have an underlying serialized representation, and my plan is to persist them (through my application UI) in an external source control system. Of course this implies that my application can check the current version of an object for updates, a merging interface for each object, etc. My question is what source control paradigm(s) and specific solution(s) to support and why. The way I (perhaps naively) see the source control world is three general paradigms: Single-repository, locked access (MS SourceSafe) Single-repository, concurrent access (CVS/SVN) Distributed (Mercurial, Git) I haven't heard of anyone using #1 for quite a number of years, so I am planning to disregard this case altogether (unless I get a compelling argument otherwise). However, I'm at a loss as to whether to support #2 or #3, and which specific implementations. I'm concerned that the use paradigms are subtly different enough that I can't adequately capture basic operations in a single UI. The last bit of information I should convey is that this application is intended to be deployed in a commercial setting, where a source control system may already be in use. I would prefer not to support more than one solution unless it's really a deal-breaker, so wide adoption in a corporate setting is a plus.

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• Guid Primary /Foreign Key dilemma SQL Server

  - by Xience

  Hi guys, I am faced with the dilemma of changing my primary keys from int identities to Guid. I'll put my problem straight up. It's a typical Retail management app, with POS and back office functionality. Has about 100 tables. The database synchronizes with other databases and receives/ sends new data. Most tables don't have frequent inserts, updates or select statements executing on them. However, some do have frequent inserts and selects on them, eg. products and orders tables. Some tables have upto 4 foreign keys in them. If i changed my primary keys from 'int' to 'Guid', would there be a performance issue when inserting or querying data from tables that have many foreign keys. I know people have said that indexes will be fragmented and 16 bytes is an issue. Space wouldn't be an issue in my case and apparently index fragmentation can also be taken care of using 'NEWSEQUENTIALID()' function. Can someone tell me, from there experience, if Guid will be problematic in tables with many foreign keys. I'll be much appreciative of your thoughts on it...

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• Clean up upon the kill signal

  - by Begui

  How do you handle clean up when the program receives a kill signal? For instance, there is an application I connect to that wants any third party app (my app) to send a finish command. What is the best say to send that finish command when my app has been destroyed with a kill -9?

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• wrapping user controls in a transaction

  - by Hans Gruber

  I'm working on heavily dynamic and configurable CMS system. Therefore, many pages are composed of a dynamically loaded set of user controls. To enable loose coupling between containers (pages) and children (user controls), all user controls are responsible for their own persistence. Each User Control is wired up to its data/service layer dependencies via IoC. They also implement an IPersistable interface, which allows the container .aspx page to issue a Save command to its children without knowledge of the number or exact nature of these user controls. Note: what follows is only pseudo-code: public class MyUserControl : IPersistable, IValidatable { public void Save() { throw new NotImplementedException(); } public bool IsValid() { throw new NotImplementedException(); } } public partial class MyPage { public void btnSave_Click(object sender, EventArgs e) { foreach (IValidatable control in Controls) { if (!control.IsValid) { throw new Exception("error"); } } foreach (IPersistable control in Controls) { if (!control.Save) { throw new Exception("error"); } } } } I'm thinking of using declarative transactions from the System.EnterpriseService namespace to wrap the btnSave_Click in a transaction in case of an exception, but I'm not sure how this might be achieved or any pitfalls to such an approach.

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• How to decide which colors to use that look most similar across most screens/monitors?

  - by Lyon

  Hi, I'm baffled. I'm trying to find suitable colors for a logo that would look similar across most monitors/screens. I know it's near impossible, but how does one end up with the color palette that new Google logo and Facebook "blue" uses for example? I've a monitor that has been calibrated, and a few laptop screens that have default settings. Yet both the Google logo and facebook's look similar (although they aren't using colors restricted to the web safe 216 palette. Any ideas? thoughts? Thanks

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• How to track history of db tables that include many-to-many mapping tables?

  - by chacmool

  I have seen several questions here on tracking db history, but can't seem to find one that matches our situation. We need to track the history of several tables, some of which are many-to-many linking tables. Eg say we have this schema: EntityA id name EntityB id name ABLink A_id B_id So, tracking changes to EntityA or EntityB seems pretty straightforward. We can keep a log table with the same columns plus a date stamp and user. But what about the links? How do we maintain the set of links that are valid for a given version of the data? We need to be able to recreate a history of the data showing changes in chronological order. So if a link added or deleted, we indicate that. Etc.

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• Understanding MongoDB (and NoSQL in general) and how to make the best use of it

  - by Earlz

  Hello, I am beginning to think that my next project I am wanting to do would work better with a NoSQL solution. The project would either involve a ton of 2-column tables or a ton of dynamic queries with dynamically generated columns in a traditional SQL database. So I feel a NoSQL database would be much cleaner. I'm looking at MongoDB and it looks pretty promising. Anyway, I'm attempting to make sense of it all. Also, I will be using MongoMapper in Ruby. Anyway though, I'm confused as to how to layout things in such a freeform database. I've read http://stackoverflow.com/questions/2170152/nosql-best-practices and the answer there says that normalization is usually bad in a NoSQL DB. So how would be the best way of laying out say a simple blog with users, posts, and comments? My natural thought was to have three collections for each and then link them by a unique ID. But this apparently is wrong? So, what are some of the ways to lay out such a thing? My concern with the answer given in the other question is, what if the author's name changed? You'd have to go through updating a ton of posts and comments. But is this an okay thing to do with NoSQL?

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• When do you trust the data / variables

  - by Wizzard

  We all know that all user data, GET/POST/Cookie etc etc needs to be validated for security. But when do you stop, once it's converted into a local variable? eg if (isValidxxx($_GET['foo']) == false) { throw InvalidArgumentException('Please enter a valid foo!'); } $foo = $_GET['foo']; fooProcessor($foo); function fooProcessor($foo) { if (isValidxxx($foo) == false) { throw Invalid...... } //other stuff } To me thats over the top. But what if you load the value from the database... I hope I make sense :)

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• Problem implementing Interceptor pattern

  - by ph0enix

  I'm attempting to develop an Interceptor framework (in C#) where I can simply implement some interfaces, and through the use of some static initialization, register all my Interceptors with a common Dispatcher to be invoked at a later time. The problem lies in the fact that my Interceptor implementations are never actually referenced by my application so the static constructors never get called, and as a result, the Interceptors are never registered. If possible, I would like to keep all references to my Interceptor libraries out of my application, as this is my way of (hopefully) enforcing loose coupling across different modules. Hopefully this makes some sense. Let me know if there's anything I can clarify... Does anyone have any ideas, or perhaps a better way to go about implementing my Interceptor pattern? Update: I came across Spring.NET. I've heard of it before, but never really looked into it. It sounds like it has a lot of great features that would be very useful for what I'm trying to do. Does anyone have any experience with Spring.NET? TIA, Jeremy

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• How to leverage Spring Integration in a real-world JMS distributed architecture?

  - by ngeek

  For the following scenario I am looking for your advices and tips on best practices: In a distributed (mainly Java-based) system with: many (different) client applications (web-app, command-line tools, REST API) a central JMS message broker (currently in favor of using ActiveMQ) multiple stand-alone processing nodes (running on multiple remote machines, computing expensive operations of different types as specified by the JMS message payload) How would one best apply the JMS support provided by the Spring Integration framework to decouple the clients from the worker nodes? When reading through the reference documentation and some very first experiments it looks like the configuration of an JMS inbound adapter inherently require to use a subscriber, which in a decoupled scenario does not exist. Small side note: communication should happen via JMS text messages (using a JSON data structure for future extensibility).

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• coding in native language

  - by radi

  is it possible to someone to invent a new programming language in his native language , and if it possible how to do that and what the tools he need to write compiler for it . thanks .

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• Just wondering what is the reason of InvalidOperationException in Enumerable.Aggregate<TSource>?

  - by the_joric

  Why only one overload throws this exception?

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• Database storage for high sample rate data in web app

  - by Jim

  I've got multiple sensors feeding data to my web app. Each channel is 5 samples per second and the data gets uploaded bundled together in 1 minute json messages (containing 300 samples). The data will be graphed using flot at multiple zoom levels from 1 day to 1 minute. I'm using Amazon SimpleDB and I'm currently storing the data in the 1 minute chunks that I receive it in. This works well for high zoom levels, but for full days there will be simply be too many rows to retrieve. The idea I've currently got is that every hour I can crawl through the data and collect together 300 samples for the last hour and store them in an hour Domain (table if you like). Does this sound like a reasonable solution? How have others implemented the same sort of systems?

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• OOP - Handling Automated Instances of a Class - PHP

  - by dscher

  This is a topic that, as a beginner to PHP and programming, sort of perplexes me. I'm building a stockmarket website and want users to add their own stocks. I can clearly see the benefit of having each stock be a class instance with all the methods of a class. What I am stumped on is the best way to give that instance a name when I instantiate it. If I have: class Stock() { ....doing stuff..... } what is the best way to give my instances of it a name. Obviously I can write: $newStock = new Stock(); $newStock.getPrice(); or whatever, but if a user adds a stock via the app, where can the name of that instance come from? I guess that there is little harm in always creating a new child with $newStock = new Stock() and then storing that to the DB which leads me to my next question! What would be the best way to retrieve 20 user stocks(for example) into instances of class Stock()? Do I need to instantiate 20 new instances of class Stock() every time the user logs in or is there something I'm missing? I hope someone answers this and more important hope a bunch of people answer this and it somehow helps someone else who is having a hard time wrapping their head around what probably leads to a really elegant solution. Thanks guys!

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• What is the best algorithm to use in creating binary trees??

  - by Hanseh

  I've been doing a research about the best algorithm to use in creating a binary tree implementation. THe top entry in my list is nested sets. Are there any other alternative or better algorithm??

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• Howto write a class where a property can be accessed without naming it.

  - by SchlaWiener

  I have a (dump) question regarding VB/C# I often use third party classes where I can access a child object with only specifying the id or key. Example: Instead of writing: DataRow row = GetAPopulatedDataRowSomeWhere(); Object result = row.Items[1]; // DataRow has no Items property Object result = row.Items["colName"]; // Also not possible I use this code to access the members: DataRow row = GetAPopulatedDataRowSomeWhere(); Object result = row[1]; Object result = row["colName"]; Can someone tell me how a class has to look like to support this syntax? My own class has a Dictionary that I want to access this way. MyClass["key"]; // <- that's what I want MyClass.SubItems["key"]; // <- that's how I use it now

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