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  • What to answer to a customer who asks which one of two equivalent technologies must be used?

    - by MainMa
    As a freelancer, I am often asked by my customers what they must choose between similar elements, neither of which being better than another. Examples: “Do I need my e-commerce website be in PHP or ASP.NET?” “Do I need to host this ordinary web service in Cloud or use an ordinary hosting service?” “Which one is better for my new website: MySQL or Oracle?” etc. There is maybe at most 1% of cases where the choice is relevant, and there is a real, objective reason to use one over another, based on the precise metrics and studies. In all other cases, it doesn't matter at all. It is totally, completely irrelevant, either because there are no implications¹, or because those implications are too small to be taken in account², or, finally, because it's impossible to predict those implications³. If you know one thing and not another one, the answer to those questions is easy: “You can either write the application in C# or Java, both being probably equivalent in your case. Note that I'm a C# developer, so if you choose Java, I would not be able to work on your project and you would need to find another freelancer.” When you know both technologies, you can't answer that. In this case, how to explain to the customer that the question he asks is subject to flamewar and has no real consequences on his project? In other words, how to explain that you've chosen to use one technology rather than an equivalent one for the reasons related to human resources, without giving the impression to be unprofessional or to not care about the project? ¹ Example: Is MySQL better (worse?), performance-wise, compared to Oracle, for a personal website which will be accessed by, oh, let's be optimistic, two people per day? ² Example: for a given project, I was asked to asset if Windows Azure hosting would be cheaper than the hosting of the same application on a well-known ASP.NET hosting provider. The cost revealed to be exactly the same. ³ Example: your customer have an idea of a future application (the idea itself being extremely vague). There is no business plan, no requirements, nothing at all. Just an idea. You are asked if Java is better than C# for this app. What do you answer?

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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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  • Is slower performance, of programming languages, really, a bad thing?

    - by Emanuil
    Here's how I see it. There's machine code and it's all that computers needs in order to run something. Computers don't care about programming languages. It doesn't matter to them whether the machine code comes from Perl, Python or PHP. Programming languages don't serve computers. They serve programmers. Some programming languages run slower than others but that's not necessarily because there is something wrong with them. In many cases, it's because they do more things that programmers would otherwise have to do (i.e. memory management) and by doing these things, they are better in what they are supposed to do - serve programmers. So, is slower performance, of programming languages, really, a bad thing?

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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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  • 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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  • Making money from a custom built interpreter?

    - by annoying_squid
    I have been making considerable progress lately on building an interpreter. I am building it from NASM assembly code (for the core engine) and C (cl.exe the Microsoft compiler for the parser). I really don't have a lot of time but I have a lot of good ideas on how to build this so it appeals to a certain niche market. I'd love to finish this but I need to face reality here ... unless I can make some good monetary return on my investment, there is not a lot of time for me to invest. So I ask the following questions to anyone out there, especially those who have experience in monetizing their programs: 1) How easy is it for a programmer to make good money from one design? (I know this is vague but it will be interesting to hear from those who have experience or know of others' experiences). 2) What are the biggest obstacles to making money from a programming design? 3) For the parser, I am using the Microsoft compiler (no IDE) I got from visual express, so will this be an issue? Will I have to pay royalties or a license fee? 4) As far as I know NASM is a 2-clause BSD licensed application. So this should allow me to use NASM for commericial development unless I am missing something? It's good to know these things before launching into the meat and potatoes of the project.

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  • I'm Sick of Web Development - What avenues are open to me ...?

    - by 5arx
    I've been working as a web developer since 1998, mostly with ASP/ASP.Net/C# but began as a Java coder (JSP mostly). Its been fun but now I'm feeling jaded and can see the need for a change. I've considered iOS/Cocoa development and Android development recently (Objective-C looks hard while I'm a former Java developer) but I'm not sure of Career opportunities being proficient in either would afford The incline of the learning curve - I just turned 40 and I know I'm not as sharp or as quick as I once was. Does anyone have any experiences/ opinions/ advice for me? Thanks.

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  • How do I add English-UK thesaurus in LibreOffice?

    - by Chethan S.
    I have been trying to use English-UK thesaurus in LibreOffice but so far cannot get it to work. I have installed mythes-en-us as only it was available in repos. As suggested in some forums I searched for openoffice.org thesaurus, but again US version was available. As a result I can't enable thesaurus when I choose English UK: As instructed elsewhere I tried this: cd /usr/share/myspell/dicts sudo ln -s th_en_US_v2.dat th_en_GB_v2.dat sudo ln -s th_en_US_v2.idx th_en_GB_v2.idx Still the result is same as shown in above screenshots. What can be done now?

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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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  • Is there a phrase or word to describe an algorithim or programme is complete in that given any value for its arguments there is a predictable outcome?

    - by Mrk Mnl
    Is there a phrase to describe an algorithim or programme is complete in that given any possible value for its arguments there is a predicatable outcome? i.e. all the ramifications have been considered whatever the context? A simple example would be the below function: function returns string get_item_type(int type_no) { if(type_no < 10) return "hockey stick" else if (type_no < 20) return "bulldozer" else return "unknown" } (excuse the dismal pseudo code) No matter what number is supplied all possibiblites are catered for. My question is: is there a word to fill the blank here: "get_item_type() is ______ complete" ? (The answer is not Turing Complete - that is something quite different - but I annoyingly always think of something as "Turing Complete" when I am thinking of the above).

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  • Looking for a real-world example illustrating that composition can be superior to inheritance

    - by Job
    I watched a bunch of lectures on Clojure and functional programming by Rich Hickey as well as some of the SICP lectures, and I am sold on many concepts of functional programming. I incorporated some of them into my C# code at a previous job, and luckily it was easy to write C# code in a more functional style. At my new job we use Python and multiple inheritance is all the rage. My co-workers are very smart but they have to produce code fast given the nature of the company. I am learning both the tools and the codebase, but the architecture itself slows me down as well. I have not written the existing class hierarchy (neither would I be able to remember everything about it), and so, when I started adding a fairly small feature, I realized that I had to read a lot of code in the process. At the surface the code is neatly organized and split into small functions/methods and not copy-paste-repetitive, but the flip side of being not repetitive is that there is some magic functionality hidden somewhere in the hierarchy chain that magically glues things together and does work on my behalf, but it is very hard to find and follow. I had to fire up a profiler and run it through several examples and plot the execution graph as well as step through a debugger a few times, search the code for some substring and just read pages at the time. I am pretty sure that once I am done, my resulting code will be short and neatly organized, and yet not very readable. What I write feels declarative, as if I was writing an XML file that drives some other magic engine, except that there is no clear documentation on what the XML should look like and what the engine does except for the existing examples that I can read as well as the source code for the 'engine'. There has got to be a better way. IMO using composition over inheritance can help quite a bit. That way the computation will be linear rather than jumping all over the hierarchy tree. Whenever the functionality does not quite fit into an inheritance model, it will need to be mangled to fit in, or the entire inheritance hierarchy will need to be refactored/rebalanced, sort of like an unbalanced binary tree needs reshuffling from time to time in order to improve the average seek time. As I mentioned before, my co-workers are very smart; they just have been doing things a certain way and probably have an ability to hold a lot of unrelated crap in their head at once. I want to convince them to give composition and functional as opposed to OOP approach a try. To do that, I need to find some very good material. I do not think that a SCIP lecture or one by Rich Hickey will do - I am afraid it will be flagged down as too academic. Then, simple examples of Dog and Frog and AddressBook classes do not really connivence one way or the other - they show how inheritance can be converted to composition but not why it is truly and objectively better. What I am looking for is some real-world example of code that has been written with a lot of inheritance, then hit a wall and re-written in a different style that uses composition. Perhaps there is a blog or a chapter. I am looking for something that can summarize and illustrate the sort of pain that I am going through. I already have been throwing the phrase "composition over inheritance" around, but it was not received as enthusiastically as I had hoped. I do not want to be perceived as a new guy who likes to complain and bash existing code while looking for a perfect approach while not contributing fast enough. At the same time, my gut is convinced that inheritance is often the instrument of evil and I want to show a better way in a near future. Have you stumbled upon any great resources that can help me?

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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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  • 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 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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  • Designing call center applications, what to consider.

    - by Espen Schulstad
    We have customers calling in to place orders. What sort of considerations should I make when building a call center application. Speed is a factor here. We had a powerbuilder application that was extremly fast for a trained user. We want to have the same sort of speed in our new production system. So some thoughts I've made are: Hotkeys are important. Is it faster to use a "wizard", step by step, or should I try to place everything important about the order logically on one sceen and have another screen where you do all searches, pertinent for that order?

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Why do programming languages allow shadowing/hiding of variables and functions?

    - by Simon
    Many of the most popular programming languges (such as C++, Java, Python etc.) have the concept of hiding / shadowing of variables or functions. When I've encountered hiding or shadowing they have been the cause of hard to find bugs and I've never seen a case where I found it necessary to use these features of the languages. To me it would seem better to disallow hiding and shadowing. Does anybody know of a good use of these concepts?

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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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  • How did we get saddled with the (hierarchical) filesystem as the basic data structure?

    - by user1936
    I'm self-taught and I don't have a CS degree. The more I've been learning about data structure, the more I wonder, in this day and age, how are we still saddled with the filesystem, with directories and files, as the basic data storage structure on the OS? I understand the simplicity of it, but it seems nowadays that there could be more options available natively. As far as I'm aware, the only project to improve the basic functionality of the filesystem was ReiserFS, where you could tell what line of a file was changed by whom, and when. For instance, if I could have native tagging for files, where I could tag images, diagrams, word-processing documents, an entire code repository, all as belonging to a single project, that would really be helpful to me. Since I'm stuck in the filesystem paradigm, I know that I could put all those into a single folder/directory, but what if they already exist in disparate directories, and they need to stay there? I know there are programs out there that can do this, but why aren't they on the filesystem? Something that would be nice to have is some kind of relational feature in the filesystem, like you get with RDBMSes. I understand that that was supposed to be part of Vista/7, but that fell off the feature list too. Sure, any program can store a binary file and have any data structure it wants in it, by why couldn't the OS offer more complex ways of storing data, beyond the simple heirarchy of the filesystem?

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