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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 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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• 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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• 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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• Expressions that are idiomatic in one language but not used or impossible in another

  - by Tungsten

  I often find myself working in unfamiliar languages. I like to read code written by others and then jump in and write something myself before going back and learning the corners of each language. To speed up this process, it really helps to know a few of the idioms you'll encounter ahead of time. Some of these, I've found are fairly unique. In Python you might do something like this: '\n'.join(listOfThings) Not all languages allow you to call methods on string literals like this. In C, you can write a loop like this: int i = 50; while(i--) { /* do something 50 times */ } C lets you decrement in the loop condition expression. Most more modern languages disallow this. Do you have any other good examples? I'm interested in often used constructions not odd corner cases.

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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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• 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 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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• 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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• Relationship between SOA and OOA

  - by TheSilverBullet

  Thomas Erl defines SOA as follows in his site: Service-oriented computing represents a new generation distributed computing platform. As such, it encompasses many things, including its own design paradigm and design principles, design pattern catalogs, pattern languages, a distinct architectural model, and related concepts, technologies, and frameworks. This definitely sounds like a whole new category which is parallel to object orientation. Almost one in which you would expect an entirely new language to exist for. Like procedural C and object oriented C#. Here is my understanding: In real life, we don't have entirely new language for SOA. And most application which have SOA architecture have an object oriented design underneath it. SOA is a "strategy" to make the entire application/service distributed and reliable. SOA needs OOPS working underneath it. Is this correct? Where does SOA (if at all it does) fit in with object oriented programming practices? Edit: I have learnt through answers that OOA and SOA work with each other and cannot be compared (in a "which is better" way). I have changed the title to "Relationship between SOA and OOA" rather than "comparison".

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• What is the annoying/lacking feature in C#, in your opinion?

  - by Vimvq1987

  To be honest, I'm working with C# everyday, and I can say that I love its elegant syntax. But no language is perfect, so does C#. In my opinion, these two features are missing: Full-featured enum. I was pretty happy with enum in C#, until I know about enum in Java. Of course, we can "simulate" a full-featured enum in C# by class, but it's much better if Microsoft simplify this. Immutable keyword. We are told to let a class/struct immutable whenever possible. But to do that, we have to add readonly keyword to every field, and then if we add setter by a mistake, our class will be mutable, and nobody knows. By immutable keyword, every field will be automatically readonly, and any setter will be prohibited (error when compile). It's like static keyword added to class in C# 2.0 well. what's is your annoying/lacking feature in C#?

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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 should NOT be included in comments? (opinion on a dictum by the inventor of Forth)

  - by AKE

  The often provocative Chuck Moore (inventor of the Forth language) gave the following advice (paraphrasing): "Use comments sparingly. Programs are self-documenting, with a modicum of help from mnemonics. Comments should say WHAT the program is doing, not HOW." My question: Should comments say WHY the program is doing what it is doing? Update: In addition to the answers below, these two provide additional insight. 1: Beginner's guide to writing comments? 2: http://programmers.stackexchange.com/a/98609/62203

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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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• 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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• Looking for terminology for the relation of a subject and a predicate

  - by kostja

  While writing some predicates for collection filtering I have stumbled over the choice of the right words for the relation of the subject and the predicate (English is a foreign language for me). What I ended up writing was "Subjects matching this predicate..." This seems to be incorrect, since predicates are functions and not regular expressions. But saying "Subjects for which this predicate returns true..." sounds awkward to me as well.. So what would be the correct term?

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• Do you write unit tests for all the time in TDD?

  - by mcaaltuntas

  I have been designing and developing code with TDD style for a long time. What disturbs me about TDD is writing tests for code that does not contain any business logic or interesting behaviour. I know TDD is a design activity more than testing but sometimes I feel it's useless to write tests in these scenarios. For example I have a simple scenario like "When user clicks check button, it should check file's validity". For this scenario I usually start writing tests for presenter/controller class like the one below. @Test public void when_user_clicks_check_it_should_check_selected_file_validity(){ MediaService service =mock(MediaService); View view =mock(View); when(view.getSelectedFile).thenReturns("c:\\Dir\\file.avi"); MediaController controller =new MediaController(service,view); controller.check(); verify(service).check("c:\\Dir\\file.avi"); } As you can see there is no design decision or interesting code to verify behaviour. I am testing values from view passed to MediaService. I usually write but don't like these kind of tests. What do yo do about these situations ? Do you write tests for all the time ? UPDATE : I have changed the test name and code after complaints. Some users said that you should write tests for the trivial cases like this so in the future someone might add interesting behaviour. But what about “Code for today, design for tomorrow.” ? If someone, including myself, adds more interesting code in the future the test can be created for it then. Why should I do it now for the trivial cases ?

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• What do you do when working with multiple languages with different capitalization schemes?

  - by dvcolgan

  I'm making a webapp using Django. The Python convention for naming variables is lowercase_with_underscores, but the Javascript convention is camelCase. In addition, I've seen many people use lowercase-with-hyphens for CSS identifiers. Would you suggest using all three naming conventions where appropriate, or picking one and using it, even if the other two recommend something else? Switching back and forth isn't a huge problem, but it can still be mental overhead.

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• How are we supposed to deal with Customers who don't give a damn?

  - by J.T.S.

  I have some customers, who expect everything for next to nothing. They also want things to be a certain way, or look a certain way, but when explaining to them why it's not a good idea, and offering suggestions, they don't listen. When things go wrong, they get moody, and demand I do something about it, but when told that it's because they wanted it that way, they don't listen. I've found that after years of being around these types of people, it's had a major impact on the way I deal with people I can't stand, and I've seriously run out of ideas. How do you deal with people who never listen, never learn, and want everything for free?

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• Why use other number bases when programming

  - by JMD

  My coworkers and I have been bending our minds to figuring out why anyone would go out of their way to program numbers in a base other than base 10. I suggested that perhaps you could optimize longer equations by putting the variables in the correct base you are working with (for instance, if you have only sets of 5 of something with no remainders you could use base 5), but I'm not sure if that's true. Any thoughts?

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• Most Useful New Technology?

  - by Craig Ferguson

  I'm looking to take a sort of sabbatical, and I'd love to use it to learn a new technology. My question is this: What's the most useful "new" technology for a software engineer to use? Node.js, iOS programming, Android, something else? I'd prefer to stay away from anything too new or experimental, since those are, in my experience, rarely actually used in professional production environments (for better or worse). Does anyone happen to have stats on how many jobs there are for each new technology or have anecdotes about how fun each one is? I've been using python/Django, so that's out, and it's similar to Ruby so i don't think learning Ruby would be that useful to expanding my skills. Anyone have any other ideas?

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• Does it really takes 5-10 years (or more) to be really good in programming?

  - by Ygam

  I don't get it. Why is there such a notion that it takes this long to be really proficient in a single language? I somehow think that this statement meant that it takes such a long time to master your language, and use it in a lot of context (web programming, desktop applications, mobile applications, etc.). Adding to that, sometimes you get stuck on a single language in your job and doing repetitive things and don't have much time to study other languages, thus for a certain amount of time, you don't really do much learning at all, and that adds to the amount of time. What do you think?

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