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• Requiring multithreading/concurrency for implementation of scripting language

  - by Ricky Stewart

  Here's the deal: I'm looking at designing my own scripting/interpreted language for fun. I'm only in the planning stages right now; I want to make sure I have a very strong hold on exactly how I will implement everything before I start coding. What I'm currently struggling with is concurrency. It seems to me like an easy way to avoid the unpredictable performance that comes with garbage collection would be to put the garbage collector in its own thread, and have it run concurrently with the interpreter itself. (To be clear, I don't plan to allow the scripts to be multithreaded themselves; I would simply put a garbage collector to work in a different thread than the interpreter.) This doesn't seem to be a common strategy for many popular scripting languages, probably for portability reasons; I would probably write the interpreter in the UNIX/POSIX threading framework initially and then port it to other platforms (Windows, etc.) if need be. Does anyone have any thoughts in this issue? Would whatever gains I receive by exploiting concurrency be nullified by the portability issues that will inevitably arise? (On that note, am I really correct in my assumption that I would experience great performance gains with a concurrent garbage collector?) Should I move forward with this strategy or step away from it?

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• Open Source Web-based CMS for writing and managing API documentation

  - by netcoder

  This is a question that have somewhat been asked before (i.e.: How to manage an open source project's documentation). However, my question is a little different because: We're not developing open source software, but proprietary software The documentation has to be hand-written, because we do not want to publish the actual software API documentation, but only the public API documentation I do want developers and project managers to write the documentation collaboratively Obviously, wikis are a solution, but they're very generic. I'm looking for a more specialized tool for this job. I've looked around and found a few like Adobe Robohelp, SaaS solutions and such, but I'd like to know if any open source software exists for that purpose. Do you know any Open Source Web-based CMS for writing and managing API and software documentation?

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• Is it bad idea to use flag variable to search MAX element in array?

  - by Boris Treukhov

  Over my programming career I formed a habit to introduce a flag variable that indicates that the first comparison has occured, just like Msft does in its linq Max() extension method implementation public static int Max(this IEnumerable<int> source) { if (source == null) { throw Error.ArgumentNull("source"); } int num = 0; bool flag = false; foreach (int num2 in source) { if (flag) { if (num2 > num) { num = num2; } } else { num = num2; flag = true; } } if (!flag) { throw Error.NoElements(); } return num; } However I have met some heretics lately, who implement this by just starting with the first element and assigning it to result, and oh no - it turned out that STL and Java authors have preferred the latter method. Java: public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) { Iterator<? extends T> i = coll.iterator(); T candidate = i.next(); while (i.hasNext()) { T next = i.next(); if (next.compareTo(candidate) > 0) candidate = next; } return candidate; } STL: template<class _FwdIt> inline _FwdIt _Max_element(_FwdIt _First, _FwdIt _Last) { // find largest element, using operator< _FwdIt _Found = _First; if (_First != _Last) for (; ++_First != _Last; ) if (_DEBUG_LT(*_Found, *_First)) _Found = _First; return (_Found); } Are there any preferences between one method or another? Are there any historical reasons for this? Is one method more dangerous than another?

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• PHP MYSQL loop to check if LicenseID Values are contained in mysql DB [closed]

  - by Jasper

  I have some troubles to find the right loop to check if some values are contained in mysql DB. I'm making a software and I want to add license ID. Each user has x keys to use. Now when the user start the client, it invokes a PHP page that check if the Key sent in the POST method is stored in DB or not. If that key isn't store than I need to check the number of his keys. If it's than X I'll ban him otherwise i add the new keys in the DB. I'm new with PHP and MYSQL. I wrote this code and I would know if I can improve it. <?php $user = POST METHOD $licenseID = POST METHOD $resultLic= mysql_query("SELECT id , idUser , idLicense FROM license WHERE idUser = '$user'") or die(mysql_error()); $resultNumber = mysql_num_rows($resultLic); $keyFound = '0'; // If keyfound is 1 the key is stored in DB while ($rows = mysql_fetch_array($resultLic,MYSQL_BOTH)) { //this loop check if the $licenseID is stored in DB or not for($i=0; $i< $resultNumber ; i++) { if($rows['idLicense'] === $licenseID) { //Just for the debug echo("License Found"); $keyFound = '1'; break; } //If key isn't in DB and there are less than 3 keys the new key will be store in DB if($keyfound == '0' && $resultNumber < 3) { mysql_query( Update users set ...Store $licenseID in Table) } // Else mean that the user want user another generated key (from the client) in the DB and i will be ban (It's wrote in TOS terms that they cant use the software on more than 3 different station) else { mysql_query( update users set ban ='1'.....etc ); } } ?> I know that this code seems really bad so i would know how i can improve it. Someone Could give me any advice? I choose to have 2 tables: users where all information about the users is, with fields id, username, password and another table license with fields id, idUsername, idLicense (the last one store license that the software generate)

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• Complex algorithm for complex problem

  - by Locaaaaa

  I got this question in an interview and I was not able to solve it. You have a circular road, with N number of gas stations. You know the ammount of gas that each station has. You know the ammount of gas you need to GO from one station to the next one. Your car starts with 0. The question is: Create an algorithm, to know from which gas station you must start driving. As an exercise to me, I would translate the algorithm to C#.

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• Separating a "wad of stuff" utility project into individual components with "optional" dependencies

  - by romkyns

  Over the years of using C#/.NET for a bunch of in-house projects, we've had one library grow organically into one huge wad of stuff. It's called "Util", and I'm sure many of you have seen one of these beasts in your careers. Many parts of this library are very much standalone, and could be split up into separate projects (which we'd like to open-source). But there is one major problem that needs to be solved before these can be released as separate libraries. Basically, there are lots and lots of cases of what I might call "optional dependencies" between these libraries. To explain this better, consider some of the modules that are good candidates to become stand-alone libraries. CommandLineParser is for parsing command lines. XmlClassify is for serializing classes to XML. PostBuildCheck performs checks on the compiled assembly and reports a compilation error if they fail. ConsoleColoredString is a library for colored string literals. Lingo is for translating user interfaces. Each of those libraries can be used completely stand-alone, but if they are used together then there are useful extra features to be had. For example, both CommandLineParser and XmlClassify expose post-build checking functionality, which requires PostBuildCheck. Similarly, the CommandLineParser allows option documentation to be provided using the colored string literals, requiring ConsoleColoredString, and it supports translatable documentation via Lingo. So the key distinction is that these are optional features. One can use a command line parser with plain, uncolored strings, without translating the documentation or performing any post-build checks. Or one could make the documentation translatable but still uncolored. Or both colored and translatable. Etc. Looking through this "Util" library, I see that almost all potentially separable libraries have such optional features that tie them to other libraries. If I were to actually require those libraries as dependencies then this wad of stuff isn't really untangled at all: you'd still basically require all the libraries if you want to use just one. Are there any established approaches to managing such optional dependencies in .NET?

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• Should all new web projects build their backend based on xml/json result sets?

  - by Blankman

  If you were building a new Saas project, would it make sense to start with all of the backend services returning xml/json? Because these days you need to build for both the web and mobile devices, and having a backend that is build from the start to return xml and json, you are ready to go mobile (all services have the business logic, so you won't be repeating anything). Now the web would be MVC, so the controller would just be routing the request to your service backend, and converting the json or xml to html. The obviousl downside is that you have to build a backend, and then another web project that calls your backend. But this also goes to you favor as it forces you to seperate your concerns, and not leak business logic in your controller/view layer. Thoughts?

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• May I use full-texted feed for my News Reader app?

  - by Mahdi Ghiasi

  I'm creating a news reader app. (Users will choose sources, but not the exact feed addresses. for example, they can choose Gizmodo but they will not see the exact url of Gizmodo's feed) Some of sources are giving partial feeds, and user must go to their website to read the complete article. My question is, May I make a fulltext version of their feed (for example, using this service) and use it instead of their feed in my News reader categories? Am I legally/ethically allowed to do this? What about using some other service like Readability? (Readability gives HTML page instead of feed as input, but anyway, output will be clean article without any advertises or such) Please note that some of these partial feeds may have some advertises inside, but the fulltext feed generators usually remove that advertises.

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• Auto update for application hosted on multiple servers on cloud

  - by mots_g

  I'm working on an application which will run on multiple Amazon EC2 instances. I wish to incorporate auto update feature for my application. The updater should update all the Ec2 instances. Also, there is a central server which governs the creation/termination of EC2 instances as per load. The central server creates a EC2 new instance from a pre-configured custom AMI (custom image which has our application pre-installed). Also, once there is an update, the pre-configured AMI needs to be updated too else it would create new instances which are not updated. Should the central server notify all the ec2 instances for an update and then the instances update themselves?Or should the application on Ec2 instance have a check for periodically updating themselves? Also how should the Amazon custom AMI be updated? Should a new instance be created from it, updated and then a new AMI be re-created and then new images be created from this AMI? What is the best way to incorporate an auto update feature for this architecture? The central server is written in Java and the application running on the cloud is written in C++. Is there a good framework available that can be used for this architecture? Please let me know on what I could be missing in the design and how it would help me to have a nice, extensible and fail safe auto update architecture. Thanks

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• Which of these design patterns is superior?

  - by durron597

  I find I tend to design class structures where several subclasses have nearly identical functionality, but one piece of it is different. So I write nearly all the code in the abstract class, and then create several subclasses to do the one different thing. Does this pattern have a name? Is this the best way for this sort of scenario? Option 1: public interface TaxCalc { String calcTaxes(); } public abstract class AbstractTaxCalc implements TaxCalc { // most constructors and fields are here public double calcTaxes(UserFinancials data) { // code double diffNumber = getNumber(data); // more code } abstract protected double getNumber(UserFinancials data); protected double initialTaxes(double grossIncome) { // code return initialNumber; } } public class SimpleTaxCalc extends AbstractCalc { protected double getNumber(UserFinancials data) { double temp = intialCalc(data.getGrossIncome()); // do other stuff return temp; } } public class FancyTaxCalc extends AbstractTaxCalc { protected double getNumber(UserFinancials data) { int temp = initialCalc(data.getGrossIncome()); // Do fancier math return temp; } } Option 2: This version is more like the Strategy pattern, and should be able to do essentially the same sorts of tasks. public class TaxCalcImpl implements TaxCalc { private final TaxMath worker; public DummyImpl(TaxMath worker) { this.worker = worker; } public double calcTaxes(UserFinancials data) { // code double analyzedDouble = initialNumber; int diffNumber = worker.getNumber(data, initialNumber); // more code } protected int initialTaxes(double grossIncome) { // code return initialNumber; } } public interface TaxMath { double getNumber(UserFinancials data, double initial); } Then I could do: TaxCalc dum = new TaxCalcImpl(new TaxMath() { @Override public double getNumber(UserFinancials data, double initial) { double temp = data.getGrossIncome(); // do math return temp; }); And I could make specific implementations of TaxMath for things I use a lot, or I could make a stateless singleton for certain kinds of workers I use a lot. So the question I'm asking is: Which of these patterns is superior, when, and why? Or, alternately, is there an even better third option?

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• How do functional languages handle random numbers?

  - by Electric Coffee

  What I mean about that is that in nearly every tutorial I've read about functional languages, is that one of the great things about functions, is that if you call a function with the same parameters twice, you'll always end up with the same result. How on earth do you then make a function that takes a seed as a parameter, and then returns a random number based on that seed? I mean this would seem to go against one of the things that are so good about functions, right? Or am I completely missing something here?

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• Any language where every class instance is a class too?

  - by Dokkat

  Taking inspiration from Javascript prototypes, I had the idea of a language where every instance can be used as a class. Before I potentially reinvent the wheel, I would like to ask if there is a language already using this concept: //To declare a Class, extend the base class (in this case, Type) Type(Weapon,{price:0}); //Same syntax to inherit; simply extend the parent: Weapon(Sword,{price:3}); Weapon(Axe,{price:4}); Sword(Katana,{price:7}); Sword(Dagger,{price:3}); //And the same to create an instance: Katana(myKatana,{nickname:"Leon"}); myKatana.price; // 7 myKatana.nickname; // Leon // An operator to return children of a class; Sword_; // [Katana, Dagger] // An operator to return array of descendants; Sword__; // [Katana, Dagger, myKatana] // An operator to return array of parents; Sword^; // Weapon // Arrays can be used as elements Sword__.price += 1; //increases price of Sword's descendants by 1 mySword.price; //8 // And to access specific element (using its name instead of index) var name = "mySword" Katana_[name]; // [mySword] Katana_[name].nickname; // Leon Has this kind of approach been already studied/implemented?

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• How to practice object oriented programming?

  - by user1620696

  I've always programmed in procedural languages and currently I'm moving towards object orientation. The main problem I've faced is that I can't see a way to practice object orientation in an effective way. I'll explain my point. When I've learned PHP and C it was pretty easy to practice: it was just matter of choosing something and thinking about an algorithm for that thing. In PHP for example, it was matter os sitting down and thinking: "well, just to practice, let me build one application with an administration area where people can add products". This was pretty easy, it was matter of thinking of an algorithm to register some user, to login the user, and to add the products. Combining these with PHP features, it was a good way to practice. Now, in object orientation we have lots of additional things. It's not just a matter of thinking about an algorithm, but analysing requirements deeper, writing use cases, figuring out class diagrams, properties and methods, setting up dependency injection and lots of things. The main point is that in the way I've been learning object orientation it seems that a good design is crucial, while in procedural languages one vague idea was enough. I'm not saying that in procedural languages we can write good software without design, just that for sake of practicing it is feasible, while in object orientation it seems not feasible to go without a good design, even for practicing. This seems to be a problem, because if each time I'm going to practice I need to figure out tons of requirements, use cases and so on, it seems to become not a good way to become better at object orientation, because this requires me to have one whole idea for an app everytime I'm going to practice. Because of that, what's a good way to practice object orientation?

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• Do ASP.Net Web Forms actually produce ADA compliant HTML? Does the ASP/AJAX toolkit undermine the goal of ADA compliance?

  - by Justin984

  I'm trying to convince my employer to let us use the Microsoft ASP/AJAX toolkit since it simplifies the implementation of many controls. However they have rejected the idea on the grounds that it produces "AJAX code" which is not ADA compliant. However the same employer requires webpages to be written in ASP.NET Web Forms which, as far as I can tell from the source, is very very far from ADA compliance. I am new to both web programming and ADA compliance. My questions are: Do ASP.Net Web Forms actually produce ADA compliant HTML? Will the ASP/AJAX toolkit undermine the goal of ADA compliance?

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• Design pattern for client/server sessions?

  - by nonot1

  Are there any common patterns or general guidance I can learn from for how to design a client/server system where the both the client and server must maintain some kind per-client session state? I've found any number of libraries that can help with some of the plumbing, but it's the overall design I'm wondering about. Open issues in my mind: How to structure the client/server communication so that bidirectional synchronous and asynchronous requests are possible? The server side needs to spawn a couple of per-connected-client session-long helper process. How to manage that? How to manage the mapping from a given client (and any of it's requests) to server state and helper process instances in the face of multiple clients and intermittent network connectivity. Most communication can be simple blocking request/reply, but some will be long running processing tasks that the client will want to keep tabs on. To the extent that it matters, the platform is Linux/C/C++. Not web based. Just an existing thick-client software app being modified to talk to backend servers for some tasks.

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• What are the design decisions involved in choosing how to expose a Java web application?

  - by Gary Rowe

  There are many ways to expose a Java web application to the consumer: application container (JBoss etc), servlet container (Tomcat etc), OSGi (Knopflerfish etc), self-executable WAR (Winstone etc) and so on. Are there any clear considerations where one approach should be favoured over another? As an example, could a collection of self-executable WARs running as raw Unix processes outperform the same applications deployed within Tomcat taking into account administration and scalability concerns?

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• Data migration - dangerous or essential?

  - by MRalwasser

  The software development department of my company is facing with the problem that data migrations are considered as potentially dangerous, especially for my managers. The background is that our customers are using a large amount of data with poor quality. The reasons for this is only partially related to our software quality, but rather to the history of the data: Most of them have been migrated from predecessor systems, some bugs caused (mostly business) inconsistencies in the data records or misentries by accident on the customer's side (which our software allowed by error). The most important counter-arguments from my managers are that faulty data may turn into even worse data, the data troubles may awake some managers at the customer and some processes on the customer's side may not work anymore because their processes somewhat adapted to our system. Personally, I consider data migrations as an integral part of the software development and that data migration can been seen to data what refactoring is to code. I think that data migration is an essential for creating software that evolves. Without it, we would have to create painful software which somewhat works around a bad data structure. I am asking you: What are your thoughts to data migration, especially for the real life cases and not only from a developer's perspecticve? Do you have any arguments against my managers opinions? How does your company deal with data migrations and the difficulties caused by them? Any other interesting thoughts which belongs to this topics?

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• How to know which fields of a record are updated in saving the edit? [closed]

  - by Luiz Maffort

  I'm recording in a log table all that is changed in a given table, so this need to know when for example the User to change the status from active to inactive. With this information I will write in my log table information of which record was changed, by whom and what was the value of old and new. If I instantiate an object before: db.Entry(chamados).State = EntityState.Modified; I can even compare, but this error appears at runtime. *An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key. * Podem me ajudar por favor?

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• When is a 'core' library a bad idea?

  - by Alex Angas

  When developing software, I often have a centralised 'core' library containing handy code that can be shared and referenced by different projects. Examples: a set of functions to manipulate strings commonly used regular expressions common deployment code However some of my colleagues seem to be turning away from this approach. They have concerns such as the maintenance overhead of retesting code used by many projects once a bug is fixed. Now I'm reconsidering when I should be doing this. What are the issues that make using a 'core' library a bad idea?

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• Approaching Java/JVM internals

  - by spinning_plate

  I've programmed in Java for about 8 years and I know the language quite well as a developer, but my goal is to deepen my knowledge of the internals. I've taken undergraduate courses in PL design, but they were very broad academic overviews (in Scheme, IIRC). Can someone suggest a route to start delving into the details? Specifically, are there particular topics (say, garbage collection) that might be more approachable or be a good starting point? Is there a decent high-level book on the internals of the JVM and the design of the Java programming language? My current approach is going to be to start with the JVM spec and research as needed.

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• Video documentary on the open source culture ?

  - by explorest

  Hello, I'm looking for some videos on these subjects: A movie/documentary detailing the origin, history, and current state of open source culture A movie/documentary on how open source software actually gets developed. What are the technical workflows. How do people create projects, recruit contributors, build a community, assign roles, track issues, assimilate new comers ... etc etc. Could someone suggest a title?

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• What should you say in post-interview?

  - by ??? Shengyuan Lu

  When you are leaving your company, you will be post-interviewed. As best practice, you shouldn't say something bad about your company, because it will "burn your bridge", another best practice is to keep silence if the company really sucks. I think if you decide to leave, there must be a reason(s) making you really unhappy, and I am sure you will have something really important to tell your employer. Then what is your attitude about post-interview?

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• Designing Mobile SMS text advertising system

  - by Ramraj Edagutti

  Currently, I am working on a product where we have an SMS text advertising system, and using this, we setup advertising campaigns for clients, and later these campaigns are sent to the end users. This is very similar to Google Adwords, but targeted to Mobile users via SMS. Just to give an overview of the system Each Campaign is mapped to an advertiser Campaign has start date and end date Campaign has a filter condition(s) or query to select the target user base from our database (to whom we send Campaigns) Target user base can be fixed, for e.g send campaign to 10000 users Target user base can also be dynamic based on query condition, for e.g send campaign to users who are active and from a particular state, district, town etc. (this way user base will be keep changing on daily basis) Campaign can have multiple campaign messages Each campaign message has start date and end date Each campaign message can have multiple message texts for different locales, for e.g English,Hindi,Telugu etc After creating an advertisement campaign, we run daily night job to provision the target user base for that a particular campaign in a separate table, and another daily job runs on morning times and checks provisioned table for campaigns and targeted users and sends the campaign to users via SMS. Problem is, current UI for creating advertising campaigns is designed in a very technical manner, I mean, normal user or business owner or clients can not use the UI to create a campaign. Below are reasons why the UI is very technical in nature Filter condition(s) or query input filed, takes user ids or mobile numbers or SQL queries. Most of times or almost every time, we use big SQL queries So we end up storing SQL queries in a database for a campaign, later we use this SQL query to fetch targeted user base. For scheduling these campaigns, we have input filed on UI which takes quartz cron expression(s) ( for e.g. send campaign on "0 0 9 1-10 MAR 2012" ), again very technical in nature Normal user or business owner, can not use the UI for creating campaigns for reasons mentioned above, Currently, we ourself (developers) helping clients to setup/create campaigns. we are trying to re-design the UI to make it more user friendly so that any user can go to UI and create an advertisement campaign by himself. I am thinking of re-designing the current UI similar to Google Adwords interface, especially for selecting target users based on user geography like country, state, city etc. I also need to select users based user subscription(s), which might make system even more complex. And also, for campaign scheduling, I am thinking of using weekdays with hours. For example, I will shows Monday to Sunday on UI, and user can select the from hours, to hours etc. Any better ideas or suggestion on how to design UI in very user friendly manner and what design should be followed on server side code (we write backend code on java/jpa/spring/quartz)? And I am looking for ideas or design patterns on how to build SQL queries (using JPA/Hinernate) programmatically on server side, based on varies conditions like based on country, state, town, village, and user subscriptions.

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• How much is modern programming still tied to underyling digital logic?

  - by New Talk

  First of all: I've got no academic background. I'm working primarily with Java and Spring and I'm also fond of web programming and relational databases. I hope I'm using the right terms and I hope that this vague question makes some sense. Today the following question came to my mind: How much is modern programming still tied to the underlying digital logic? With modern programming I mean concepts like OOP, AOP, Java 7, AJAX, … I hope you get the idea. Do they no longer need the digital logic with which computers are working internally? Or is binary logic still ubiquitous when programming this way? If I'd change the inner workings of a computer overnight, would it matter, because my programming techniques are already that abstract? P. S.: With digital logic I mean the physical representation of everything "inside" the computer as zeroes and ones. Changed "binary" to "digital".

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• Adding complexity to remove duplicate code

  - by Phil

  I have several classes that all inherit from a generic base class. The base class contains a collection of several objects of type T. Each child class needs to be able to calculate interpolated values from the collection of objects, but since the child classes use different types, the calculation varies a tiny bit from class to class. So far I have copy/pasted my code from class to class and made minor modifications to each. But now I am trying to remove the duplicated code and replace it with one generic interpolation method in my base class. However that is proving to be very difficult, and all the solutions I have thought of seem way too complex. I am starting to think the DRY principle does not apply as much in this kind of situation, but that sounds like blasphemy. How much complexity is too much when trying to remove code duplication? EDIT: The best solution I can come up with goes something like this: Base Class: protected T GetInterpolated(int frame) { var index = SortedFrames.BinarySearch(frame); if (index >= 0) return Data[index]; index = ~index; if (index == 0) return Data[index]; if (index >= Data.Count) return Data[Data.Count - 1]; return GetInterpolatedItem(frame, Data[index - 1], Data[index]); } protected abstract T GetInterpolatedItem(int frame, T lower, T upper); Child class A: public IGpsCoordinate GetInterpolatedCoord(int frame) { ReadData(); return GetInterpolated(frame); } protected override IGpsCoordinate GetInterpolatedItem(int frame, IGpsCoordinate lower, IGpsCoordinate upper) { double ratio = GetInterpolationRatio(frame, lower.Frame, upper.Frame); var x = GetInterpolatedValue(lower.X, upper.X, ratio); var y = GetInterpolatedValue(lower.Y, upper.Y, ratio); var z = GetInterpolatedValue(lower.Z, upper.Z, ratio); return new GpsCoordinate(frame, x, y, z); } Child class B: public double GetMph(int frame) { ReadData(); return GetInterpolated(frame).MilesPerHour; } protected override ISpeed GetInterpolatedItem(int frame, ISpeed lower, ISpeed upper) { var ratio = GetInterpolationRatio(frame, lower.Frame, upper.Frame); var mph = GetInterpolatedValue(lower.MilesPerHour, upper.MilesPerHour, ratio); return new Speed(frame, mph); }

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