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• Examples of Hierarchical-Model-View-Controller (HMVC)?

  - by Stephen

  Hi, I'm interested in the Presentation-Abstraction-Control? (aka Hierarchical-Model-View-Controller (HMVC)) Architectural Pattern for constructing complex user interfaces (GUI or web) and was wondering if anyone was aware of any examples in the wild where I could read the code? My list so far; Cairngorm framework for Adobe Flex any others I'm aware of the JavaWorld article and associated letters cited in the wikipedia article http://en.wikipedia.org/wiki/Presentation-abstraction-control

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• Implementing database redundancy with sharded tables

  - by ensnare

  We're looking to implement load balancing by horizontally sharding our tables across a cluster of servers. What are some options to implement live redundancy should a server fail? Would it be effective to do (2) INSERTS instead of one ... one to the target shard, and another to a secondary shard which could be accessed should the primary shard not respond? Or is there a better way? Thanks.

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• Is it possible to create a quine in every turing-complete language?

  - by sub

  I just wanted to know if it is 100% possible, if my language is turing-complete, to write a program in it that prints itself out (of course not using a file reading function) So if the language just has the really necessary things in order to make it turing complete (I would prove that by translating Brainf*ck code to it), like output, variables, conditions and gotos (hell yes, gotos), can I try writing a quine in it? I'm also asking this because I'm not sure that a quine directly fits into Turing's law that the turing machine is capable of any computational task. I just want to know so I don't try for years without knowing that it may be impossible.

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• how to generate dbml file from Sybase database?

  - by 5YrsLaterDBA

  I think we may have trouble with our existing project. For some reasons we have to switch from SQL Server to Sybase SQL Anywhere 11. now we trying to find a way continue use our existing LINQ code. We wish we can still use L2S? If cannot, we wish we can use L2E, then we have to change to ADO. how to generate dbml file from Sybase Anywhere 11? after that can we use sqlmetal to generate .cs files?

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• Querying a Cassandra column family for rows that have not been updated in X days

  - by knorv

  I'm moving an existing MySQL based application over to Cassandra. So far finding the equivalent Cassandra data model has been quite easy, but I've stumbled on the following problem for which I'd appreciate some input: Consider a MySQL table holding millions of entities: CREATE TABLE entities ( id INT AUTO_INCREMENT NOT NULL, entity_information VARCHAR(...), entity_last_updated DATETIME, PRIMARY KEY (id), KEY (entity_last_updated) ); The table is regularly queried for entities that need to be updated: SELECT id FROM entities WHERE entity_last_updated IS NULL OR entity_last_updated < DATE_ADD(NOW(), INTERVAL -7*24 HOUR) ORDER BY entity_last_updated ASC; The entities returned by this queries are then updated using the following query: UPDATE entities SET entity_information = ?, entity_last_updated = NOW() WHERE id = ?; What would be the corresponding Cassandra data model that would allow me to store the given information and effectively query the entities table for entities that need to be updated (that is: entities that have not been updated in the last seven days)?

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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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• Are SOLID principles really solid?

  - by Arseny

  The first pattern stands for this acronym is SRP. Here is a quote. the single responsibility principle states that every object should have a single responsibility, and that responsibility should be entirely encapsulated by the class. That's is simple and clear till we start to code ) Suppose we have a class with well defined SRP. To serialize this class instances we need to add special atrributes to that class. So now the class have other responsibility. Dosen't it violate SRP? Let's see other story. Interface implementation. Then we implement an interface we simply add other responsibility say dispose its resorces or compare its instances or whatever. So my question. Is it possible to keep SRP complete? How can we do it?

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• Ideas for web development practical jokes?

  - by Ellie P.

  I am a web developer for a Django-based site for a student organization, and I have the opportunity to make the website temporarily absurd for a day of general campus-wide debauchery and chaos (long story, doesn't matter.) What are your best ideas for web development practical jokes (that you could never use in the real world)? For example, one idea we had was to use a client-side script to convert each character to its upside down equivalent in Unicode, si?? ??i? ?ui????os. I'm not necessarily looking for Django-specific solutions. I imagine most of these things would happen on the front-end. I am also quite aware that usability will suffer considerably--the point is to be fun for a day, and there will always be a link to the normal version of the site. Also, everything must be relatively cosmetic and easily reversible--I'm happy to swap out static CSS/JS/HTML/templates/images, and even temporarily add a django view, but no messing with the data level!

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• Is DataAdapter use facade pattern or Adapter pattern.

  - by Krirk

  When i see Update(),Fill() method of DataAdapter object I always think Is DataAdapter use facade pattern ? It looks like behind the scenes It will create Command object, Connection object and execute it for us. Or DataAdapter use Adapter pattern because it is adapter between Dataset and Comamand object ,Connection object ?

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• XML flat file vs. relational database backend

  - by donpal

  Most projects now need some form of a database. When someone says database, I usually think relational databases, but I still hear about flat file XML databases. What parameters do you take into consideration when deciding between a "real" database and a flat-file XML database. When should one be used over the other, and under what circumstances should I never consider using a flat file (or vice versa a relational) database?

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• Method signature Vs function prototype

  - by Maroloccio

  A formal definition of the two? Current Wiki articles denote their different contexts and applications, such as internal type signature "strings" in Java VMs (1) and C/C++ function prototypes informing compilers of upcoming method definitions (2) but... 1) http://en.wikipedia.org/wiki/Type_signature 2) http://en.wikipedia.org/wiki/Function_prototype ... where to look for a definition which clearly and formally distinguished one from the other? There is literature using the words prototype and signature almost interchangeably yet other uses appear strict and consistent, if language-specific. Background: I am writing documentation for a sample compiler written for a University project.

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• Do fluent interfaces violate the Law of Demeter?

  - by Jakub Šturc

  The wikipedia article about Law of Demeter says: The law can be stated simply as "use only one dot". However a simple example of a fluent interface may look like this: static void Main(string[] args) { new ZRLabs.Yael.Pipeline("cat.jpg") .Rotate(90) .Watermark("Monkey") .RoundCorners(100, Color.Bisque) .Save("test.png"); } So does this goes together?

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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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• Stack and Hash joint

  - by Alexandru

  I'm trying to write a data structure which is a combination of Stack and HashSet with fast push/pop/membership (I'm looking for constant time operations). Think of Python's OrderedDict. I tried a few things and I came up with the following code: HashInt and SetInt. I need to add some documentation to the source, but basically I use a hash with linear probing to store indices in a vector of the keys. Since linear probing always puts the last element at the end of a continuous range of already filled cells, pop() can be implemented very easy without a sophisticated remove operation. I have the following problems: the data structure consumes a lot of memory (some improvement is obvious: stackKeys is larger than needed). some operations are slower than if I have used fastutil (eg: pop(), even push() in some scenarios). I tried rewriting the classes using fastutil and trove4j, but the overall speed of my application halved. What performance improvements would you suggest for my code? What open-source library/code do you know that I can try?

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• Loose Coupling vs. Information Hiding and Ease of Change

  - by cretzel

  I'm just reading Code Complete by Steve McConell and I'm thinking of an Example he gives in a section about loose coupling. It's about the interface of a method that calculates the number of holidays for an employee, which is calculated from the entry date of the employee and her sales. The author suggests a to have entry date and sales as the parameters of the method instead of an instance of the employee: int holidays(Date entryDate, Number sales) instead of int holidays(Employee emp) The argument is that this decouples the client of the method because it does not need to know anything about the Employee class. Two things came to my mind: Providing all the parameters that are needed for the calculation breaks encapsulation. It shows the internals of the method on how it computes the result. It's harder to change, e.g. when someone decides that also the age of the employee should be included in the calculation. One would have to change the signature. What's your opinion?

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• Create Class functions on the fly?

  - by JasonS

  Hi, i have a validation class which needs improving. If I require some custom validation I need to specify a custom function. It works a bit like this: The controller tells the validation that a custom validation function is required. The controller runs the validation. --- Gets iffy here --- Validation class creates a new instance of the controller class.... Validation class runs controller-custom_validation_function() Validation class returns true / false Is there someway that I can alter this to do something like this? $validation = new validation; // Insert rules here. $validation-function() = $this-function(); By doing this I could get rid of the step of creating an unneeded class instance.

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• Building big, immutable objects without constructors having long parameter lists

  - by Malax

  Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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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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• WPF: Sort of inconsistence in the visual appearence of WPF controls derived by Selector class

  - by msfanboy

  Hello, focused items == selected items but selected items != focused items. Have you ever wondered about that? Do you specially style the backcolor of a focused/selected item ? I ask this question because a user has an enabled button because some customer items are selected. The user is wondering now "why the heck can I delete this customers (button is enabled...) when I have just clicked on the orders control selecting some orders ready to delete (button is enabled too). The thing is the selected customer items are nearly looking grayed out in the default style... Well its sort of inconsistence to the user NOT to the programmer because WE know the behavior. Do you cope with stuff like that?

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• Google search results : How to find the minimum window that contains all the search keywords?

  - by Algorist

  Hi, I was wondering what will the complexity of the algorithm that is used to find the smallest snippet that contains all the search key words. Please explain the complexity, if non-trivial. Thanks Bala

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• best way to store 1:1 user relationships in relational database

  - by aharon

  What is the best way to store user relationships, e.g. friendships, that must be bidirectional (you're my friend, thus I'm your friend) in a rel. database, e.g. MYSql? I can think of two ways: Everytime a user friends another user, I'd add two rows to a database, row A consisting of the user id of the innitiating user followed by the UID of the accepting user in the next column. Row B would be the reverse. You'd only add one row, UID(initiating user) followed by UID(accepting user); and then just search through both columns when trying to figure out whether user 1 is a friend of user 2. Surely there is something better?

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• Semantic Grid System, Media Query issue

  - by Andy

  I'm using the Semantic Grid System to build a responsive site. However, something isn't quite right with the media queries that should obviously kick in once it hits a particular screen size. I'll reference what i mean with their example on the website : if I view this on my iPhone for example, given that it is supposed to adjust to a single column structure on a mobile device, it still throws out the web version of the page. That is true for both Safari and Chrome on my iPhone. However, if I use the RWD bookmarklet to check it's appearance at different resolutions it appears as expected for the mobile resolution. Also, ironically, if I resize the page in Safari on my desktop it also adjusts accordingly once I get down to the approriate screen size, but not in Firefox. The media query that it uses once it hits 720px is @media screen and (max-width: 720px) { #maincolumn, #sidebar { .column(12); margin-bottom: 1em; } } and I might be wide of the mark here but I think that must be the issue. But given that this is directly from the semantic.gs website I'm not inclined to question their own code. Any idea what the problem might be?

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• Modeling a Generic Relationship in a Database

  - by StevenH

  This is most likely one for all you sexy DBAs out there: How would I effieciently model a relational database whereby I have a field in an "Event" table which defines a "SportType". This "SportsType" field can hold a link to different sports tables E.g. "FootballEvent", "RubgyEvent", "CricketEvent" and "F1 Event". Each of these Sports tables have different fields specific to that sport. My goal is to be able to genericly add sports types in the future as required, yet hold sport specific event data (fields) as part of my Event Entity. Is it possible to use an ORM such as NHibernate / Entity framework which would reflect such a relationship? I have thrown together a quick C# example to express my intent at a higher level: public class Event<T> where T : new() { public T Fields { get; set; } public Event() { EventType = new T(); } } public class FootballEvent { public Team CompetitorA { get; set; } public Team CompetitorB { get; set; } } public class TennisEvent { public Player CompetitorA { get; set; } public Player CompetitorB { get; set; } } public class F1RacingEvent { public List<Player> Drivers { get; set; } public List<Team> Teams { get; set; } } public class Team { public IEnumerable<Player> Squad { get; set; } } public class Player { public string Name { get; set; } public DateTime DOB { get; set;} }

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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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• What is the best "forgot my password" method?

  - by Edward Tanguay

  I'm programming a community website. I want to build a "forgot my password" feature. Looking around at different sites, I've found they employ one of three options: send the user an email with a link to a unique, hidden URL that allows him to change his password (Gmail and Amazon) send the user an email with a new, randomly generated password (Wordpress) send the user his current password (www.teach12.com) Option #3 seems the most convenient to the user but since I save passwords as an MD5 hash, I don't see how option #3 would be available to me since MD5 is irreversible. This also seems to be insecure option since it means that the website must be saving the password in clear text somewhere, and at the least the clear-text password is being sent over insecure e-mail to the user. Or am I missing something here? So if I can't do option #1, option #2 seems to be the simplest to program since I just have to change the user's password and send it to him. Although this is somewhat insecure since you have to have a live password being communicated via insecure e-mail. However, this could also be misused by trouble-makers to pester users by typing in random e-mails and constantly changing passwords of various users. Option #1 seems to be the most secure but requires a little extra programming to deal with a hidden URL that expires etc., but it seems to be what the big sites use. What experience have you had using/programming these various options? Are there any options I've missed?

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