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• JAVA vs .NET - Choice for way to go further [closed]

  - by Sarang

  I have my subject .Net acedemically. I also learned core Java and did a project as well. I took training from a Java firm. Now, as a skill I do have knowledge as both language. But, it is creating a large problem to me that, which field I should chhose? Even if having better OOP fundamentals, will it be easier for me to transfer from one to another in the future ? Please suggest me a way. Also, we do have may technologies available at both side, like JSP, JSF, J2ME, Share Point, SilverLight etc. Which is better as per their reliabity point of view? Which are fast growing and useful technologies used mostly in current IT corporate world ? Are they easier to learn at fresher's point of view? Please answer. Perhaps, this answer may help me mostly to create my way to learn them and go further. Every IT developer, please help to find me my way.

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• SQL Stored Queries - use result of query as boolean based on existence of records

  - by Christian Mann

  Just getting into SQL stored queries right now... anyway, here's my database schema (simplified for YOUR convenience): member ------ id INT PK board ------ id INT PK officer ------ id INT PK If you're into OOP, Officer Inherits Board Inherits Member. In other words, if someone is listed on the officer table, s/he is listed on the board table and the member table. I want to find out the highest privilege level someone has. So far my SP looks like this: DELIMITER // CREATE PROCEDURE GetAuthLevel(IN targetID MEDIUMINT) BEGIN IF SELECT `id` FROM `member` WHERE `id` = targetID; THEN IF SELECT `id` FROM `board` WHERE `id` = targetID; THEN IF SELECT `id` FROM `officer` WHERE `id` = targetID; THEN RETURN 3; /*officer*/ ELSE RETURN 2; /*board member*/ ELSE RETURN 1; /*general member*/ ELSE RETURN 0; /*not a member*/ END // DELIMITER ; The exact text of the error is #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT id FROM member WHERE id = targetID; THEN IF SEL' at line 4 I suspect the issue is in the arguments for the IF blocks. What I want to do is return true if the result-set is at least one -- i.e. the id was found in the table. Do any of you guys see anything to do here, or should I reconsider my database design into this:? person ------ id INT PK level SMALLINT

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• Alternative Python standard library reference

  - by Ender

  I love Python; I absolutely despise its official documentation. Tutorials do not count as library references, but that appears to be what they're attempting. What I really want is the ability to find a class in the standard library and view documentation for all of its properties and methods. Actionscript, MSDN, and Java all do this just fine (although each with their odd quirks). Where is this for python? For example, I wanted to sort a list. mylist.sort(). Awesome. But what if I wanted it sorted in descending order? Official documentation is not - much - help. Or what if I wanted to specify a key function? That's also supported: mylist.sort(key=lamba item: item.customVar)- but documented...where? I understand that Python's approach to OOP may not be equivalent to Java et. al. Maybe list isn't actually a class - maybe it's just a function that returns an iterable when the tachyon beams are set to glorious and the unboxed hyper enumeration is quantized, but...I don't care. I just want to know how to sort lists. (Apologies for the angst - too much caffeine today)

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• Programming Technique: How to create a simple card game

  - by Shyam

  Hi, As I am learning the Ruby language, I am getting closer to actual programming. So I was thinking of creating a simple card game. My question isn't Ruby orientated, but I do know want to learn how to solve this problem with a genuine OOP approach. In my card game I want to have four players. Using a standard deck with 52 cards, no jokers/wildcards. In the game I won't use the Ace as a dual card, it is always the highest card. So, the programming problems I wonder about are the following: How can I sort/randomize the deck of cards? There are four types, each having 13 values. Eventually there can be only unique values, so picking random values could generate duplicates. How can I implement a simple AI? As there are tons of card games, someone would have figured this part out already, so references would be great. I am a truly Ruby nuby, and my goal here is to learn to solve problems, so pseudo code would be great, just to understand how to solve the problem programmatically. I apologize for my grammar and writing style if it's unclear, for it is not my native language. Also pointers to sites where such challenges are explained, would be a great resource! Thank you for your comments, answers and feedback!

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• Objective-C Simple Inheritance and OO Principles

  - by bleeckerj

  I have a subclass SubClass that inherits from baseclass BaseClass. BaseClass has an initializer, like so: -(id)init { self = [super init]; if(self) { [self commonInit]; } return self; } -(void)commonInit { self.goodStuff = [[NSMutableArray alloc]init]; } SubClass does its initializer, like so: -(id)init { self = [super init]; if(self) { [self commonInit]; } return self; } -(void)commonInit { self.extraGoodStuff = [[NSMutableArray alloc]init]; } Now, I've *never taken a proper Objective-C course, but I'm a programmer more from the Electrical Engineering side, so I make do. I've developed server-side applications mostly in Java though, so I may be seeing the OO world through Java principles. When SubClass is initialized, it calls the BaseClass init and my expectation would be — because inheritance to me implies that characteristics of a BaseClass pass through to SubClass — that the commonInit method in BaseClass would be called during BaseClass init. It is not. I can *sorta understand maybe-possibly-stretch-my-imagination why it wouldn't be. But, then — why wouldn't it be based on the principles of OOP? What does "self" represent if not the instance of the class of the running code? Okay, so — I'm not going to argue that what a well-developed edition of Objective-C is doing is wrong. So, then — what is the pattern I should be using in this case? I want SubClass to have two main bits — the goodStuff that BaseClass has as well as the extraGoodStuff that it deserves as well. Clearly, I've been using the wrong pattern in this type of situation. Am I meant to expose commonInit (which makes me wonder about encapsulation principles — why expose something that, in the Java world at least, would be considered "protected" and something that should only ever be called once for each instance)? I've run into a similar problem in the recent past and tried to muddle through it, but now — I'm really wondering if I've got my principles and concepts all straight in my head. Little help, please.

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• Disassembling with python - no easy solution?

  - by Abc4599

  Hi, I'm trying to create a python script that will disassemble a binary (a Windows exe to be precise) and analyze its code. I need the ability to take a certain buffer, and extract some sort of struct containing information about the instructions in it. I've worked with libdisasm in C before, and I found it's interface quite intuitive and comfortable. The problem is, its Python interface is available only through SWIG, and I can't get it to compile properly under Windows. At the availability aspect, diStorm provides a nice out-of-the-box interface, but it provides only the Mnemonic of each instruction, and not a binary struct with enumerations defining instruction type and what not. This is quite uncomfortable for my purpose, and will require a lot of what I see as spent time wrapping the interface to make it fit my needs. I've also looked at BeaEngine, which does in fact provide the output I need, a struct with binary info concerning each instruction, but its interface is really odd and counter-intuitive, and it crashes pretty much instantly when provided with wrong arguments. The CTypes sort of ultimate-death-to-your-python crashes. So, I'd be happy to hear about other solutions, which are a little less time consuming than messing around with djgcc or mingw to make SWIGed libdisasm, or writing an OOP wrapper for diStorm. If anyone has some guidance as to how to compile SWIGed libdisasm, or better yet, a compiled binary (pyd or dll+py), I'd love to hear/have it. :) Thanks ahead.

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• How to make Doxygen ignore specific PHP functions, when generating documentation from a purely proce

  - by Senthil

  I am writing a PHP Library and I am trying out Doxygen to generate the API documentation. My library does not use OOP. All code is procedural. I use lot of helper functions which have an _ (underscore) prefix in their names. They are not part of the publicly exposed API. They are just used internally. Even though they are commented just like the API functions, I don't want them included when giving out the documentation for the API. I want Doxygen to ignore these functions. I can think of two solutions for this, but I am not able to implement either one of them. First is, I can set some configuration in Doxygen to make it ignore specific function name patterns. I went through Doxygen help documentation and searched the web. There seems to be options to ignore file and folder name patterns. But I am not able to find an option to specify a function name pattern and make it ignore those functions. Second is, along with all the other content in the comments above functions, I could add some other keyword or something and make Doxygen ignore those functions. I haven't been able to find out how to do that either. How can I make Doxygen ignore specific PHP functions when generating documentation? Update I searched within Stack Overflow and came across this question. It looked similar to my question. I found out about EXCLUDE_SYMBOLS config option in one of the answers. You can use that to exclude function names too. More importantly, wildcards were supported. So I am able to ignore all my functions with _ as the prefix :) This ridiculous! I should've done more research :| Someone please delete this question or add this answer as an answer.

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• How to convince someone, that reading programming related books(blogs, so..) is important? [closed]

  - by hgulyan

  Dear all, please, help me to convince, that no matter what you're doing, you need to read some stuff, try to learn something new. They say, that they don't want to sit in front of computer in the end of a day and they don't have opportunity to read in working hours, or they're too tired for doing something. Have you faced this kind of situation? What did you do? What if you want to help them? What methodology you'd suggest? How to open their eyes? EDIT I'm really concerned about this people. EDIT 2 Just to be clear, I'm not talking about one person or two. Some of them, just do their job good. Company doesn't motivate them to learn something. They're not bad people, not bad developers, they just need something or someone to help, show another view, but you can't just describe this new view or say smth like "You need to learn!" and that's it, you'll start to learn or you're not a good programmer. I started to learn OOP, DB structure 6 years ago and I had someone who had guided me. He told me to learn Java and MySQL, gave me some manuals and API's. That's how I started. What if they don't have that kind person or something else?

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• Why is VB6 still so widely used?

  - by Uri

  Note that this question is not meant to start an argument, I am genuinely curious: Back in the 90s I used to work for a large CPU maker and we were building some debuggers. All our core logic was in C++, but the GUI was made in VB6. We couldn't figure out MFC and it was too much a hassle. We glued together VB6 and C++ using COM which we created via ATL. Fast forward to 2009, having been mostly in the Java world I am looking at job boards and seeing more VB6 jobs than I expected. I genuinely thought that VB6 was extinct, especially since VB.NET supposedly solved a lot of the problems with the VB6 which at the time felt a lot like a scripting language than a true OOP language. So what happened? Why is new code still written in it? Isn't there a better way to glue C++ and VB.NET? Note that I haven't used VB.NET, I just understand that it is a much more "stricter" language than VB6 was. Even with Option Explicit or whatever it was.

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• How do I get an overview and a methodology for programming in Python

  - by Peter Nielsen

  I've started to learn Python and programming from scratch. I have not programmed before so it's a new experience. I do seem to grasp most of the concepts, from variables to definitions and modules. I still need to learn a lot more about what the different libraries and modules do and also I lack knowledge on OOP and classes in Python. I see people who just program in Python like that's all they have ever done and I am still just coming to grips with it. Is there a way, some tools, a logical methodology that would give me an overview or a good hold of how to handle programming problems ? For instance, I'm trying to create a parser which we need at the office . I also need to create a spider that would collect links from various websites. Is there a formidable way of studying the various modules to see what is needed ? Or is it just nose to the grind stone and understand what the documentation says ? Sorry for the lengthy question..

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• PHP syntax for referencing self with late static binding

  - by Chris

  When I learned PHP it was pretty much in procedural form, more recently I've been trying to adapt to the OOP way of doing things. Hoever the tutorials I've been following were produced before PHP 5.3 when late static binding was introduced. What I want to know is how do I reference self when calling a function from a parent class. For example these two methods were written for a User class which is a child of DatabaseObject. Right now they're sitting inside the User class, but, as they're used in other child classes of DatabaseObject I'd like to promote them to be included inside DatabaseObject. public static function find_all() { global $database; $result_set = self::find_by_sql("select * from ".self::$table_name); return $result_set; } and: protected function cleaned_attributes() { global $database; $clean_attributes = array(); foreach($this->attributes() as $key => $value) { $clean_attributes[$key] = $database->escape_value($value); } return $clean_attributes; } So I have three questions: 1) How do I change the self:: reference when I move it to the parent. Is it static:: or something similar? 2) When calling the function from my code do I call it in the same way, as a function of the child class eg User::find_all() or is there a change there also? 3) Is there anything else I need to know before I start chopping bits up?

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• Php: Overriding abstract method goes wrong

  - by Lu4

  Hi! I think there is a problem in php's OOP implementation. EDIT: Consider more illustrative example: abstract class Animal { public $name; // public function Communicate(Animal $partner) {} // Works public abstract function Communicate(Animal $partner); // Gives error } class Panda extends Animal { public function Communicate(Panda $partner) { echo "Hi {$partner->name} I'm a Panda"; } } class Human extends Animal { public function Communicate(Human $partner) { echo "Hi {$partner->name} I'm a Human"; } } $john = new Human(); $john->name = 'John'; $mary = new Human(); $mary->name = 'Mary'; $john->Communicate($mary); // should be ok $zuzi = new Panda(); $zuzi->name = 'Zuzi'; $zuzi->Communicate($john); // should give error The problem is that when Animal::Communicate is an abstract method, php tells that the following methods are illegal: "public function Communicate(Panda $partner)" "public function Communicate(Human $partner)" but when Animal::Communicate is non-abstract but has zero-implementation Php thinks that these methods are legal. So in my opinion it's not right because we are doing override in both cases, and these both cases are equal, so it seems like it's a bug... Older part of the post: Please consider the following code: Framework.php namespace A { class Component { ... } abstract class Decorator { public abstract function Decorate(\A\Component $component); } } Implementation.php namespace B { class MyComponent extends \A\Component { ... } } MyDecorator.php namespace A { class MyDecorator extends Decorator { public function Decorate(\B\MyComponent $component) { ... } } } The following code gives error in MyDecorator.php telling Fatal error: Declaration of MyDecorator::Decorate() must be compatible with that of A\Decorator::Decorate() in MyDecorator.php on line ... But when I change the Framework.php::Decorator class to the following implementation: abstract class Decorator { public function Decorate(\A\Component $component) {} } the problem disappears.

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• How large a role does subjectiveness play in programming?

  - by Bob

  I often read about the importance of readability and maintainability. Or, I read very strong opinions about which syntax features are bad or good. Or discussions about the values of certain paradigms, like OOP. Aside from that, this same question floats about in my mind whenever I read debates on SO or Meta about subjective questions. Or read questions about best practices and sometimes find myself or others disagreeing. What role does subjectiveness play within the programming realm? Sometimes I think it plays a large role. Software developers are engineers in a way, but also people. A large part of programming is dealing with code that's human readable. This is very different from Math or Physics or other disciplines with very exact and structured rules. Here the exact structure and rules are largely up in the air, changeable on a whim, and hence the amount of languages in existence. And one person may find one language very readable, and another person may find their own language the most comforting. The same with practices. One person may not like certain accepted practices. I myself find splitting classes into different files very unreadable, for instance. But, I can't say rules haven't helped in general. Certain practices have and do make life easier. And new languages have given rise to syntax and structure that make life easier. There's certainly been a progression towards code that is easier to read and maintain even given a largely diverse group of people. So maybe these things aren't as subjective as I thought. It reminds me, in a way, of UI design. Certainly it's subjective, but then there's an entire discipline involved in crafting good UI and it tends to work. Is there something non-subjective about the ideas behind maintainability, readability, and other best practices? Is there something tangible to grasp when one develops a new language or thinks of new practices?

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• Java (or possibly other languages) learning path

  - by bgo

  I am familiar (as a self-learner) with C, python and php such that i can solve some problems involving simple steps (for example, i easily do calculations for physics lab reports with python which normally would take 4x-5x times longer with a calculator). The point here is, as doing such things, i learnt the idea / concepts of programming language and problem solving along with oop or fuctional programming etc. Recently i have started Java and, with the familiarity of other languages, i am doing well for starters but i need guidence. -I am thinking of learning syntax from sun java tutorials and then practicing with codingbat.com or similar sites. I need a reference book that i can study deeper aspects of the topics i am learning. What do you suggest about these? -The problem is (and always have been) the lack of practice. I need coding and problem-solving practices sources. I stuck at the point where i can't figure out what to do next. Can you suggest any source (possibly like codingbat)? If i could plan a learning trail, i can progress faster and efficiently. So i need ideas, comments, suggestions. Thanks in advance.

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• COM-Objects containing maps / content error(0)

  - by Florian Berzsenyi

  I'm writing a small wrapper to get familiar with some important topics in C++ (WinAPI, COM, STL,OOP). For now, my class shall be able to create a (child) window. Mainly, this window is connected to a global message loop that distribute messages to a local loop of the right instance (global is static, local is virtual). Obviously, there are surely better ways to do that but I'm using std::maps to store HWND and their instance pointer in pairs (the Global loop looks for the pointer with the HWND-parameter, gets itself the pointer from the map and calls then the local loop). Now, it appears that the map does not accept any values because of a unknown reason. It seems to allocate enough space but something went wrong anyway [ (error) 0 is displayed instead of the entries in visual C++). I've looked that up in google as well and found out that maps cause some trouble when used in classes AND DLLs. May this be the reason and is there any solution?? Protected scope of class: static std::map<HWND,MAP_BASE_OBJECT*> m_LoopBuf Implementation in .cpp-file: std::map<HWND,MAP_BASE_OBJECT*> HWindow::m_LoopBuf;

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• Optimizing C# code in MVC controller

  - by cc0

  I am making a number of distinct controllers, one relating to each stored procedure in a database. These are only used to read data and making them available in JSON format for javascripts. My code so far looks like this, and I'm wondering if I have missed any opportunities to re-use code, maybe make some help classes. I have way too little experience doing OOP, so any help and suggestions here would be really appreciated. Here is my generalized code so far (tested and works); using System; using System.Configuration; using System.Web.Mvc; using System.Data; using System.Text; using System.Data.SqlClient; using Prototype.Models; namespace Prototype.Controllers { public class NameOfStoredProcedureController : Controller { char[] lastComma = { ',' }; String oldChar = "\""; String newChar = "&quot;"; StringBuilder json = new StringBuilder(); private String strCon = ConfigurationManager.ConnectionStrings["SomeConnectionString"].ConnectionString; private SqlConnection con; public StoredProcedureController() { con = new SqlConnection(strCon); } public string do_NameOfStoredProcedure(int parameter) { con.Open(); using (SqlCommand cmd = new SqlCommand("NameOfStoredProcedure", con)) { cmd.CommandType = CommandType.StoredProcedure; cmd.Parameters.AddWithValue("@parameter", parameter); using (SqlDataReader reader = cmd.ExecuteReader()) { while (reader.Read()) { json.AppendFormat("[{0},\"{1}\"],", reader["column1"], reader["column2"]); } } con.Close(); } if (json.Length.ToString().Equals("0")) { return "[]"; } else { return "[" + json.ToString().TrimEnd(lastComma) + "]"; } } //http://host.com/NameOfStoredProcedure?parameter=value public ActionResult Index(int parameter) { return new ContentResult { ContentType = "application/json", Content = do_NameOfStoredProcedure(parameter) }; } } }

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• How should a programmer go about getting started with Flash/Flex/ActionScript?

  - by Graphics Noob

  What is the shortest path between zero (ie no flash related development software on my computer or information about where to obtain it or get started) to running a "hello world" ActionScript? I'm hoping for an answer that gives step by step instructions about exactly what software is needed to get started, an example of some "hello world" code, and instructions for compiling and running the code. I've spent more time than I think should be necessary researching this question and not found much information. Hopefully this question will be found by programmers like me who want to get started with Flash/Flex/ActionScript (After my morning of researching I still don't even know what terminology to use so I'll just throw it all out there). ActionScript tutorials I've found are focused on programming concepts, ie logic, branching, OOP, etc, and some even have code examples to download, but not a single one I've found explains how to compile and run the code. They all seem to assume you have an IDE standing by but no knowledge of programming, exactly the opposite of the position I'm in. Here are the most related SO questions I've found: http://stackoverflow.com/questions/59083/what-is-adobe-flex-is-it-just-flash-ii http://stackoverflow.com/questions/554899/getting-started-with-flex-3-ui-actionscript-programming http://stackoverflow.com/questions/2123105/how-to-learn-flex

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• Methods and properties in scheme - is object oriented programming possible in scheme?

  - by incrediman

  I will use a simple example to illustrate my question. In Java, C, or any other OOP language, I could create a pie class in a way similar to this: class Apple{ public String flavor; public int pieces; private int tastiness; public goodness(){ return tastiness*pieces; } } What's the best way to do that with Scheme? I suppose I could do with something like this: (define make-pie (lambda (flavor pieces tastiness) (list flavor pieces tastiness))) (define pie-goodness (lambda (pie) (* (list-ref pie 1) (list-ref pie 2)))) (pie-goodness (make-pie 'cherry 2 5)) ;output: 10 ...where cherry is the flavor, 2 is the pieces, and 5 is the tastiness. However then there's no type-safety or visibility, and everything's just shoved in an unlabeled list. How can I improve that? Sidenote: The make-pie procedure expects 3 arguments. If I want to make some of them optional (like I'd be able to in curly-brace languages like Java or C), is it good practice to just take the arguments in as a list (that is treat the arguments as a list - not require one argument which is a list) and deal with them that way?

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• VB.net httpwebrequest For loop hangs every 10 or so iterations

  - by user574632

  Hello, I am trying to loop through an array and perform an httpwebrequest in each iteration. The code seems to work, however it pauses for a while (eg alot longer than the set timeout. Tried setting that to 100 to check and it still pauses) after every 10 or so iterations, then carries on working. Here is what i have so far: For i As Integer = 0 To numberOfProxies - 1 Try 'create request to a proxyJudge php page using proxy Dim request As HttpWebRequest = HttpWebRequest.Create("http://www.pr0.net/deny/azenv.php") request.Proxy = New Net.WebProxy(proxies(i)) 'select the current proxie from the proxies array request.Timeout = 10000 'set timeout Dim response As HttpWebResponse = request.GetResponse() Dim sr As StreamReader = New StreamReader(response.GetResponseStream()) Dim pageSourceCode As String = sr.ReadToEnd() 'check the downloaded source for certain phrases, each identifies a type of proxy 'HTTP_X_FORWARDED_FOR identifies a transparent proxy If pageSourceCode.Contains("HTTP_X_FORWARDED_FOR") Then 'delegate method for cross thread safe UpdateListbox(ListBox3, proxies(i)) ElseIf pageSourceCode.Contains("HTTP_VIA") Then UpdateListbox(ListBox2, proxies(i)) Else UpdateListbox(ListBox1, proxies(i)) End If Catch ex As Exception 'MessageBox.Show(ex.ToString) used in testing UpdateListbox(ListBox4, proxies(i)) End Try completedProxyCheck += 1 lblTotalProxiesChecked.CustomInvoke(Sub(l) l.Text = completedProxyCheck) Next I have searched all over this site and via google, and most responses to this type of question say the response must be closed. I have tried a using block, eg: Using response As HttpWebResponse = request.GetResponse() Using sr As StreamReader = New StreamReader(response.GetResponseStream()) Dim pageSourceCode As String = sr.ReadToEnd() 'check the downloaded source for certain phrases, each identifies a type of proxy 'HTTP_X_FORWARDED_FOR identifies a transparent proxy If pageSourceCode.Contains("HTTP_X_FORWARDED_FOR") Then 'delegate method for cross thread safe UpdateListbox(ListBox3, proxies(i)) ElseIf pageSourceCode.Contains("HTTP_VIA") Then UpdateListbox(ListBox2, proxies(i)) Else UpdateListbox(ListBox1, proxies(i)) End If End Using End Using And it makes no difference (though i may have implemented it wrong) As you can tell im very new to VB or any OOP so its probably a simple problem but i cant work it out. Any suggestions or just tips on how to diagnose these types of problems would be really appreciated.

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• How do interpreters functions written in the class C++ in the main

  - by T_Geek

  Hi I'm working on a project about Data structures. In the first , I wrote everything in main but it sounds like C . But as I learned, I tried to thinkk OOP and do as little as possible in my main() methods. I've implemented some opertation in my class like add,delet,find.it's too easy to implement its . class ARB { private: struct BT { int data; BT *l; BT *r; }; struct BT *p; public ARB(); ~ARB(); void del(int n); void add(int n); }; void ARB::del(int num) { //The code ,don't care about it }; main() { // BTR T; T.add(3); T.add(5); }; But I arrived to the big program How can I define a methode which have to use a binary tree and to get a stack STACK ARB::MyFunct(BT* p) { // The code don't care about it } How can I apply it in the main programme main() { // BT T; T.add(3); T.add(5); STACK S; BT* p S=T.MyFunct(p); // error C2664 cannot convert parametre 1 }; **mention :I implement STACK class

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• SQL, MVC, Entity Framework

  - by Anthony

  Hi Im using the above technologies and have ran into what I presume is a design issue I have made. I have an Artwork table in my DB and have been able to add art (I now think of these as Digital Products) to a shopping cart + CartLine table fine. The system I have that adds art to galleries and user accounts etc works fine. Now the client wants to sell T-shirts, Mugs and Pens etc, 'HardwareProducts' so I have created a 'HardwareProducts' table. Now I have two different product types in two tables. I use GUID's as the PK's in both the HardwareProducts table and Artwork table. When a customer adds an item to their cart I store the GUID in the ProductID column in the CartItems table. The issue is the database will not know which table to reference when I bring the LineItem object up through my ORM to the front end. In OOP I can see how you would have a base class of Product, and then a DigitalProduct class and HardwareProduct class drived from it, but how do you model this in SQL Server and the Entity Framework please, or is there another way?

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• C# using the "this" keyword in this situation?

  - by Alex

  Hi, I've completed a OOP course assignment where I design and code a Complex Number class. For extra credit, I can do the following: Add two complex numbers. The function will take one complex number object as a parameter and return a complex number object. When adding two complex numbers, the real part of the calling object is added to the real part of the complex number object passed as a parameter, and the imaginary part of the calling object is added to the imaginary part of the complex number object passed as a parameter. Subtract two complex numbers. The function will take one complex number object as a parameter and return a complex number object. When subtracting two complex numbers, the real part of the complex number object passed as a parameter is subtracted from the real part of the calling object, and the imaginary part of the complex number object passed as a parameter is subtracted from the imaginary part of the calling object. I have coded this up, and I used the this keyword to denote the current instance of the class, the code for my add method is below, and my subtract method looks similar: public ComplexNumber Add(ComplexNumber c) { double realPartAdder = c.GetRealPart(); double complexPartAdder = c.GetComplexPart(); double realPartCaller = this.GetRealPart(); double complexPartCaller = this.GetComplexPart(); double finalRealPart = realPartCaller + realPartAdder; double finalComplexPart = complexPartCaller + complexPartAdder; ComplexNumber summedComplex = new ComplexNumber(finalRealPart, finalComplexPart); return summedComplex; } My question is: Did I do this correctly and with good style? (using the this keyword)?

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• Ways to gain a deeper understanding of programming concepts?

  - by MrPlow

  I'm a marketer and have been messing around in PHP/MySQL for years. Recently (the last several months) I've been making my own scripts/programs in Python and I've really enjoyed the whole problem solving process. I've read(skimmed) some books and understand the basics of OOP, polymorphism, etc.. I have a general interest in AI and Natural Language in particular but it seems these things require a masters in Computer Science. My knowledge of math is poor. The last class I took was calculus, and I've forgotten the majority of it. Basically I'm looking for things to learn that will help me think in a more analytic way, and maybe see solutions where I didn't before. Improving my ability to program in Python would be nice too. I don't need to learn a specific language or something for employment, just enjoyment. Although my work often involves web development so some utility would be nice. I don't like learning concepts by just reading them. I need to apply them, even if the examples are contrived. A recommendation of a couple good books or other resources would be nice. :) Apologies if this is too vague/misplaced...

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• Avoid loading unnecessary data from db into objects (web pages)

  - by GmGr

  Really newbie question coming up. Is there a standard (or good) way to deal with not needing all of the information that a database table contains loaded into every associated object. I'm thinking in the context of web pages where you're only going to use the objects to build a single page rather than an application with longer lived objects. For example, lets say you have an Article table containing id, title, author, date, summary and fullContents fields. You don't need the fullContents to be loaded into the associated objects if you're just showing a page containing a list of articles with their summaries. On the other hand if you're displaying a specific article you might want every field loaded for that one article and maybe just the titles for the other articles (e.g. for display in a recent articles sidebar). Some techniques I can think of: Don't worry about it, just load everything from the database every time. Have several different, possibly inherited, classes for each table and create the appropriate one for the situation (e.g. SummaryArticle, FullArticle). Use one class but set unused properties to null at creation if that field is not needed and be careful. Give the objects access to the database so they can load some fields on demand. Something else? All of the above seem to have fairly major disadvantages. I'm fairly new to programming, very new to OOP and totally new to databases so I might be completely missing the obvious answer here. :)

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• Learning Haskell maps, folds, loops and recursion

  - by Darknight

  I've only just dipped my toe in the world of Haskell as part of my journey of programming enlightenment (moving on from, procedural to OOP to concurrent to now functional). I've been trying an online Haskell Evaluator. However I'm now stuck on a problem: Create a simple function that gives the total sum of an array of numbers. In a procedural language this for me is easy enough (using recursion) (c#) : private int sum(ArrayList x, int i) { if (!(x.Count < i + 1)) { int t = 0; t = x.Item(i); t = sum(x, i + 1) + t; return t; } } All very fine however my failed attempt at Haskell was thus: let sum x = x+sum in map sum [1..10] this resulted in the following error (from that above mentioned website): Occurs check: cannot construct the infinite type: a = a -> t Please bear in mind I've only used Haskell for the last 30 minutes! I'm not looking simply for an answer but a more explanation of it. Thanks in advanced.

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