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• System that splits passwords across two servers

  - by Burning the Codeigniter

  I stumbled upon this news article on BBC, RSA splits passwords in two to foil hackers' attacks tl;dr - a (randomized) password is split in half and is stored across two separate servers, to foil hackers that gained access to either server upon a security breach. Now the main question is, how would this kind of system would be made... codespeaking, for PHP which I commonly develop on my web applications, the database password is normally stored in a configuration file, i.e. config.php with the username and password, in that case it is understandable that the passwords can be stolen if the security was compromised. However when splitting and sending the other half to the other server, how would this go on when making a communication to the other server (keeping in mind with PHP) since the other server password would be stored in a configuration file, wouldn't it? In terms of security is to keep the other server password away from the main one, just exactly how would the main server communicate, without exposing any other password, apart from the first server. This certainly makes me think...

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• I've been told that Exceptions should only be used in exceptional cases. How do I know if my case is exceptional?

  - by tieTYT

  My specific case here is that the user can pass in a string into the application, the application parses it and assigns it to structured objects. Sometimes the user may type in something invalid. For example, their input may describe a person but they may say their age is "apple". Correct behavior in that case is roll back the transaction and to tell the user an error occurred and they'll have to try again. There may be a requirement to report on every error we can find in the input, not just the first. In this case, I argued we should throw an exception. He disagreed, saying, "Exceptions should be exceptional: It's expected that the user may input invalid data, so this isn't an exceptional case" I didn't really know how to argue that point, because by definition of the word, he seems to be right. But, it's my understanding that this is why Exceptions were invented in the first place. It used to be you had to inspect the result to see if an error occurred. If you failed to check, bad things could happen without you noticing. Without exceptions every level of the stack needs to check the result of the methods they call and if a programmer forgets to check in one of these levels, the code could accidentally proceed and save invalid data (for example). Seems more error prone that way. Anyway, feel free to correct anything I've said here. My main question is if someone says Exceptions should be exceptional, how do I know if my case is exceptional?

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• internal error message pops up after each time system is rebooted

  - by Biju

  I had installed ubuntu 12.04 using wubi. But each time i boot the system an internal error message pops up. As show below:- Executable path /usr/share/apport/apport-gpu-error-intel.py Package xserver-xorg-video-intel 2:2.17.0-1ubuntu4 Problem Type crash Apportversion 2.0.1-0ubuntu7 and so on.. I had earlier upgraded to ubuntu 12.04 from ubuntu 11.10. And encountered the same issue. Hence i uninstalled the OS and reinstalled using wubi. I had posted the same query in ubuntu.com/support (Question Number: 195525) But couldnt find a solution. I am using dell inspiron with intel pentium. Need ur help in resolving this issue. thanking u, Biju

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• Harmful temptations in programming

  - by gaearon

  Just curious, what kinds of temptations in programming turned out to be really harmful in your projects? Like when you really feel the urge to do something and you believe it's going to benefit the project or else you just trick yourself into believing it is, and after a week you realize you haven't solved any real problems but instead created new ones or, in the best case, pleased your inner beast with no visible impact. Personally, I find it very hard to not refactor bad code. I work with a lot of bad legacy code, and it takes some deep breaths to not touch it when I have no tests to prove my refactoring doesn't not break anything. Another demon for me in user interface, I can literally spend hours changing UI layout just because I enjoy doing it. Sometimes I tell myself I'm working on usability, but the truth is just I love moving buttons around. What are your programming demons, and how do you avoid them?

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• If the model is validating the data, shouldn't it throw exceptions on bad input?

  - by Carlos Campderrós

  Reading this SO question it seems that throwing exceptions for validating user input is frowned upon. But who should validate this data? In my applications, all validations are done in the business layer, because only the class itself really knows which values are valid for each one of its properties. If I were to copy the rules for validating a property to the controller, it is possible that the validation rules change and now there are two places where the modification should be made. Is my premise that validation should be done on the business layer wrong? What I do So my code usually ends up like this: <?php class Person { private $name; private $age; public function setName($n) { $n = trim($n); if (mb_strlen($n) == 0) { throw new ValidationException("Name cannot be empty"); } $this->name = $n; } public function setAge($a) { if (!is_int($a)) { if (!ctype_digit(trim($a))) { throw new ValidationException("Age $a is not valid"); } $a = (int)$a; } if ($a < 0 || $a > 150) { throw new ValidationException("Age $a is out of bounds"); } $this->age = $a; } // other getters, setters and methods } In the controller, I just pass the input data to the model, and catch thrown exceptions to show the error(s) to the user: <?php $person = new Person(); $errors = array(); // global try for all exceptions other than ValidationException try { // validation and process (if everything ok) try { $person->setAge($_POST['age']); } catch (ValidationException $e) { $errors['age'] = $e->getMessage(); } try { $person->setName($_POST['name']); } catch (ValidationException $e) { $errors['name'] = $e->getMessage(); } ... } catch (Exception $e) { // log the error, send 500 internal server error to the client // and finish the request } if (count($errors) == 0) { // process } else { showErrorsToUser($errors); } Is this a bad methodology? Alternate method Should maybe I create methods for isValidAge($a) that return true/false and then call them from the controller? <?php class Person { private $name; private $age; public function setName($n) { $n = trim($n); if ($this->isValidName($n)) { $this->name = $n; } else { throw new Exception("Invalid name"); } } public function setAge($a) { if ($this->isValidAge($a)) { $this->age = $a; } else { throw new Exception("Invalid age"); } } public function isValidName($n) { $n = trim($n); if (mb_strlen($n) == 0) { return false; } return true; } public function isValidAge($a) { if (!is_int($a)) { if (!ctype_digit(trim($a))) { return false; } $a = (int)$a; } if ($a < 0 || $a > 150) { return false; } return true; } // other getters, setters and methods } And the controller will be basically the same, just instead of try/catch there are now if/else: <?php $person = new Person(); $errors = array(); if ($person->isValidAge($age)) { $person->setAge($age); } catch (Exception $e) { $errors['age'] = "Invalid age"; } if ($person->isValidName($name)) { $person->setName($name); } catch (Exception $e) { $errors['name'] = "Invalid name"; } ... if (count($errors) == 0) { // process } else { showErrorsToUser($errors); } So, what should I do? I'm pretty happy with my original method, and my colleagues to whom I have showed it in general have liked it. Despite this, should I change to the alternate method? Or am I doing this terribly wrong and I should look for another way?

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• What is the single most effective thing you did to improve your programming skills?

  - by Oded

  Looking back at my career and life as a programmer, there were plenty of different ways I improved my programming skills - reading code, writing code, reading books, listening to podcasts, watching screencasts and more. My question is: What is the most effective thing you have done that improved your programming skills? What would you recommend to others that want to improve? I do expect varied answers here and no single "one size fits all" answer - I would like to know what worked for different people. Edit: Wow - what great answers! Keep 'em coming people!!!

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• How do I access the system tray?

  - by Jon

  So I'm messing around with Natty a little, and I noticed that all the apps that would normally use the system tray (or "notification area"?) aren't displaying there. Is that a bug, or is that the way it's going to be? I heard something about Ubuntu getting rid of that feature entirely. Is there a way to add it back? I mean, I didn't really like it, either, especially when there were apps that used it unnecessarily, but I can't use CryptKeeper at all now, or easycrypt, and I don't know whether Dropbox has synced without opening Nautilus.

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• Preferred lambda syntax?

  - by Roger Alsing

  I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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• Why appending to a list in Scala should have O(n) time complexity?

  - by Jubbat

  I am learning Scala at the moment and I just read that the execution time of the append operation for a list (:+) grows linearly with the size of the list. Appending to a list seems like a pretty common operation. Why should the idiomatic way to do this be prepending the components and then reversing the list? It can't also be a design failure as implementation could be changed at any point. From my point of view, both prepending and appending should be O(1). Is there any legitimate reason for this?

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• Object-based content management system

  - by Adam Maras

  I remember hearing within the last year or two about a content management system either being released or developed that was centralized around product/item information. I'm aware that there are several CMSes that have this capability, but this particular one was built specifically for that task. Also, I remember it winning some sort of award or recognition for upcoming software products. However, I can't for the life of me remember what this CMS was called or who was developing it. Does anyone know what package I'm talking about?

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• Locomotion-system with irregular IK

  - by htaunay

  Im having some trouble with locomtions (Unity3D asset) IK feet placement. I wouldn't call it "very bad", but it definitely isn't as smooth as the Locomotion System Examples. The strangest behavior (that is probably linked to the problem) are the rendered foot markers that "guess" where the characters next step will be. In the demo, they are smooth and stable. However, in my project, they keep flickering, as if Locomotion changed its "guess" every frame, and sometimes, the automatic defined step is too close to the previous step, or sometimes, too distant, creating a very irregular pattern. The configuration is (apparently)Identical to the human example in the demo, so I guessing the problem is my model and/or animation. Problem is, I can't figure out was it is =S Has anyone experienced the same problem? I uploaded a video of the bug to help interpreting the issue (excuse the HORRIBLE quality, I was in a hurry).

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• Why don't languages include implication as a logical operator?

  - by Maciej Piechotka

  It might be a strange question, but why there is no implication as a logical operator in many languages (Java, C, C++, Python Haskell - although as last one have user defined operators its trivial to add it)? I find logical implication much clearer to write (particularly in asserts or assert-like expressions) then negation with or: encrypt(buf, key, mode, iv = null) { assert (mode != ECB --> iv != null); assert (mode == ECB || iv != null); assert (implies(mode != ECB, iv != null)); // User-defined function }

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• How to make a queue switches from FIFO mode to priority mode?

  - by enzom83

  I would like to implement a queue capable of operating both in the FIFO mode and in the priority mode. This is a message queue, and the priority is first of all based on the message type: for example, if the messages of A type have higher priority than the messages of the B type, as a consequence all messages of A type are dequeued first, and finally the messages of B type are dequeued. Priority mode: my idea consists of using multiple queues, one for each type of message; in this way, I can manage a priority based on the message type: just take first the messages from the queue at a higher priority and progressively from lower priority queues. FIFO mode: how to handle FIFO mode using multiple queues? In other words, the user does not see multiple queues, but it uses the queue as if it were a single queue, so that the messages leave the queue in the order they arrive when the priority mode is disabled. In order to achieve this second goal I have thought to use a further queue to manage the order of arrival of the types of messages: let me explain better with the following code snippet. int NUMBER_OF_MESSAGE_TYPES = 4; int CAPACITY = 50; Queue[] internalQueues = new Queue[NUMBER_OF_MESSAGE_TYPES]; Queue<int> queueIndexes = new Queue<int>(CAPACITY); void Enqueue(object message) { int index = ... // the destination queue (ie its index) is chosen according to the type of message. internalQueues[index].Enqueue(message); queueIndexes.Enqueue(index); } object Dequeue() { if (fifo_mode_enabled) { // What is the next type that has been enqueued? int index = queueIndexes.Dequeue(); return internalQueues[index].Dequeue(); } if (priority_mode_enabled) { for(int i=0; i < NUMBER_OF_MESSAGE_TYPES; i++) { int currentQueueIndex = i; if (!internalQueues[currentQueueIndex].IsEmpty()) { object result = internalQueues[currentQueueIndex].Dequeue(); // The following statement is fundamental to a subsequent switching // from priority mode to FIFO mode: the messages that have not been // dequeued (since they had lower priority) remain in the order in // which they were queued. queueIndexes.RemoveFirstOccurrence(currentQueueIndex); return result; } } } } What do you think about this idea? Are there better or more simple implementations?

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• How to fix "error: unknown file system" on all available partitions

  - by Jonathan

  I've had a running problem with removing Linux from my Windows 7 laptop. Initially, it was installed as a dual-boot, and worked well. To remove, I deleted the partitions on my laptop. This removed grub, and I was left with needing to enter: set root=... set prefix=... insmod normal normal each restart. I didn't restore the Windows boot-loader and have since re-partitioned my drive. Now, upon reaching the command prompt screen, an ls query showshd0, with three partitions, but none of them have a recognizable boot-loader as each returns with error: unknown file system. Booting from a Windows 7 rescue disk doesn't seem to work, as it sends me to the same command prompt terminal. All I'm looking to do is restore the boot-loader, either grub or Windows 7. Any help would be appreciated. Thanks in advance.

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• wordpress hosting uk help [closed]

  - by Neenee Kale

  Hi so i am planning to develop a website (student information system) for my final year project. I am going to use wordpress and i am a beginner so i just found out i have to purchase a host if i am not going to use wordpress.com as my host. which i dont want to as there is loads of limitations if i want to build a website. so therefore i want to purchase my own host which is cheap and i pay for a year i the most i will pay is 50 pounds. could someone please recommend me a very good uk based word press host which will allow me to build a information system where people will be able to login and enter their details etc. I have researched many hosts by I need someone to recommend me what features are important to build a information system like this. I am a beginner in wordpress so therefore i dont have much idea on hostings.. thank you

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• System crashes when internet connection is unplugged

  - by Rincewind

  When i first tried to install any ubuntu newer than 10.04 on my netbook (Acer aspire one 722 11,6" WXGA - C-60 Dual Core APU - AMD Radeon HD 6250 - 1x HDMI - 2GB DDR3 - 320GB - 802.11bgN - 6CELL2.2 - BT 3.0 - VGA Webcam), it would fail to boot. I found out that the only fix to this was linking it to the internet via lan-cable during the installation. However, after installing ubuntu 12.04 successfully my system is crashing everytime i unplug the lan-cable. My first thought was disabling the netbook´s w-lan (via the band at the top) but it was not fixing the problem. Looking on the taskmanager ('top') during the process brought no further insight, no process was exploding or something like that. As i am out of guesses help would be really appreaciated. Lg Rincewind

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• Motivation Problems, Middle School Programmer [closed]

  - by Anonymous

  I'm in middle school at the moment and have been programming for about a year and a half. I mostly work with Python and Ruby, and am currently learning Rails. I know, you can never learn enough, it takes a looong time to master a subject, but I feel like I don't have much left to learn :(. I've learned many concepts in Python, learned basically the whole std lib and have written a ton of programs, same with Ruby. In Ruby I've also done a lot of metaprogramming. After I've learned all the concepts, and written a lot of programs, there is nothing really left for me to do! What can I do, now that I've learned all the concepts, and written some programs? I can't get a job working with real developers, and the programming camp I went to last year was far too easy.

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• How do I use an API?

  - by GRardB

  Background I have no idea how to use an API. I know that all APIs are different, but I've been doing research and I don't fully understand the documentation that comes along with them. There's a programming competition at my university in a month and a half that I want to compete in (revolved around APIs) but nobody on my team has ever used one. We're computer science majors, so we have experience programming, but we've just never been exposed to an API. I tried looking at Twitter's documentation, but I'm lost. Would anyone be able to give me some tips on how to get started? Maybe a very easy API with examples, or explaining essential things about common elements of different APIs? I don't need a full-blown tutorial on Stack Overflow; I just need to be pointed in the right direction. Update The programming languages that I'm most fluent in are C (simple text editor usually) and Java (Eclipse). In an attempt to be more specific with my question: I understand that APIs (and yes, external libraries are what I was referring to) are simply sets of functions. Question I guess what I'm trying to ask is how I would go about accessing those functions. Do I need to download specific files and include them in my programs, or do they need to be accessed remotely, etc.?

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• When should one use "out" parameters?

  - by qegal

  In Objective-C, there are several methods like initWithContentsOfFile:encoding:error: where one passes in a reference to an NSError object for the error: parameter. In this example, the value of the NSError object passed in can change based on what goes on at runtime when the method is being called and whether the body of the method was executed in a certain way successfully. In a way I think of this NSError object as sort of like a second return value from the method, and only differs from an object anObject in the statement return anObject; in that when this statement is called, execution leaves the method. So my question is, not only in the context of error handling in Objective-C, but in general, when should one use an "out" parameter in place of returning said value in a return statement?

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• Why are slower programming languages considered worse than faster ones?

  - by Emanuil

  Here's how I see it. There's machine code and it's all that the computers needs in order to run something. The computers don't care about programming languages. It doesn't matter to them if the machine code comes from Perl, Python or PHP. Programming languages exist to serve programmers. Some programming languages run slower then others but that's not because there is something wrong with them. It's often because they do more things that otherwise programmers would do and by doing these things, they do better what they are supposed to do - serve programmers. So why are slower programming languages considered worse than faster ones?

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• What is the worst programmer habit?

  - by 0x4a6f4672

  Many people get into programming because programming is fun. At least in the beginning. After some time doing it professionally, programming is no longer fun, often just hard work. Sometimes we develop bad habits along the way to make it fun again. Some bad habits of programmers are well known, for example the "I fix that in a second" habit, the "reinvent the wheel" practice or the "all code except mine is crap" attitude (which often leads to "I will re-write the entire program from scratch" syndrome). There are things which a programmer should never do. What is the worst programmer habit?

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• Why the static data members have to be defined outside the class separately in C++ (unlike Java)?

  - by iammilind

  class A { static int foo () {} // ok static int x; // <--- needed to be defined separately in .cpp file }; I don't see a need of having A::x defined separately in a .cpp file (or same file for templates). Why can't be A::x declared and defined at the same time? Has it been forbidden for historical reasons? My main question is, will it affect any functionality if static data members were declared/defined at the same time (same as Java) ?

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• Reboot to fail safe mode when root file system is full

  - by Richard

  I have a system running on a 4GB Nandrive. When the drive is full, Ubuntu will not boot :( and I have to plug in a rescue thumbdrive to delete files. The problem is the hardware is not easily accessible except via network. Is there a sure-fire way to boot Ubuntu, say, to RAM or other means when the disk is full or on any other errors in the normal boot process? In other words, is there a fallback rescue boot mode with networking? Thanks for any advice.

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• TDD, new tests while old ones not implemented yet

  - by liori

  I am experimenting with test-driven development, and I found that I often come to a following situation: I write tests for some functionality X. Those tests fail. While trying to implement X, I see that I need to implement some feature Y in a lower layer of my code. So... I write tests for Y. Now both tests for X and Y fail. Once I had 4 features in different layers of code being worked on at the same time, and I was losing my focus on what I am actually doing (too many tests failing at the same time). I think I could solve this by putting more effort into planning my tasks even before I start writing tests. But in some cases I didn't know that I will need to go deeper, because e.g. I didn't know the API of lower layer very well. What should I do in such cases? Does TDD have any recommendations?

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• Inventory management system design problem

  - by Steve F

  What are the conventions for item batch identifiers in inventory management systems? For example: A retail supermarket can order 'Item X' from either 'Supplier A' or 'Supplier B'. When it completes an order for the item from either supplier, it needs to store the record of the receipt. Inventory quantity for the item is increased upon receipt of the order. However it is also required to store some record of the supplier. Thus some sort of batch identifier is required. This batch identifier will uniquely identify the item received and the supplier from whom it is received. A new batch is created each time items are received in stock (for example, after an order). Hence, for purposes of accounting / auditing, information available to identify an item after it was sold comprises of ITEM_CODE, ITEM_NAME, BATCH_CODE. The BATCH_CODE is unique and is associated with DATE_RECEIVED, SUPPLIER_CODE, QTY_RECEIVED. Is this a complete system specification for the above scenario or has anything significant been left out?

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