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  • I don't know C. And why should I learn it?

    - by Stephen
    My first programming language was PHP (gasp). After that I started working with JavaScript. I've recently done work in C#. I've never once looked at low or mid level languages like C. The general consensus in the programming-community-at-large is that "a programmer who hasn't learned something like C, frankly, just can't handle programming concepts like pointers, data types, passing values by reference, etc." I do not agree. I argue that: Because high level languages are easily accessible, more "non-programmers" dive in and make a mess In order to really get anything done in a high level language, one needs to understand the same similar concepts that most proponents of "learn-low-level-first" evangelize about. Some people need to know C; those people have jobs that require them to write low to mid-level code. I'm sure C is awesome, and I'm sure there are a few bad programmers who know C. Why the bias? As a good, honest, hungry programmer, if I had to learn C (for some unforeseen reason), I would learn C. Considering the multitude of languages out there, shouldn't good programmers focus on learning what advances us? Shouldn't we learn what interests us? Should we not utilize our finite time moving forward? Why do some programmers disagree with this? I believe that striving for excellence in what you do is the fundamental deterministic trait between good programmers and bad ones. Does anyone have any real world examples of how something written in a high level language—say Java, Pascal, PHP, or Javascript—truely benefitted from a prior knowledge of C? Examples would be most appreciated.

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  • How to write constructors which might fail to properly instantiate an object

    - by whitman
    Sometimes you need to write a constructor which can fail. For instance, say I want to instantiate an object with a file path, something like obj = new Object("/home/user/foo_file") As long as the path points to an appropriate file everything's fine. But if the string is not a valid path things should break. But how? You could: 1. throw an exception 2. return null object (if your programming language allows constructors to return values) 3. return a valid object but with a flag indicating that its path wasn't set properly (ugh) 4. others? I assume that the "best practices" of various programming languages would implement this differently. For instance I think ObjC prefers (2). But (2) would be impossible to implement in C++ where constructors must have void as a return type. In that case I take it that (1) is used. In your programming language of choice can you show how you'd handle this problem and explain why?

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  • Misconceptions about purely functional languages?

    - by Giorgio
    I often encounter the following statements / arguments: Pure functional programming languages do not allow side effects (and are therefore of little use in practice because any useful program does have side effects, e.g. when it interacts with the external world). Pure functional programming languages do not allow to write a program that maintains state (which makes programming very awkward because in many application you do need state). I am not an expert in functional languages but here is what I have understood about these topics until now. Regarding point 1, you can interact with the environment in purely functional languages but you have to explicitly mark the code (functions) that introduces them (e.g. in Haskell by means of monadic types). Also, AFAIK computing by side effects (destructively updating data) should also be possible (using monadic types?) but is not the preferred way of working. Regarding point 2, AFAIK you can represent state by threading values through several computation steps (in Haskell, again, using monadic types) but I have no practical experience doing this and my understanding is rather vague. So, are the two statements above correct in any sense or are they just misconceptions about purely functional languages? If they are misconceptions, how did they come about? Could you write a (possibly small) code snippet illustrating the Haskell idiomatic way to (1) implement side effects and (2) implement a computation with state?

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  • Can higher-order functions in FP be interpreted as some kind of dependency injection?

    - by Giorgio
    According to this article, in object-oriented programming / design dependency injection involves a dependent consumer, a declaration of a component's dependencies, defined as interface contracts, an injector that creates instances of classes that implement a given dependency interface on request. Let us now consider a higher-order function in a functional programming language, e.g. the Haskell function filter :: (a -> Bool) -> [a] -> [a] from Data.List. This function transforms a list into another list and, in order to perform its job, it uses (consumes) an external predicate function that must be provided by its caller, e.g. the expression filter (\x -> (mod x 2) == 0) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] selects all even numbers from the input list. But isn't this construction very similar to the pattern illustrated above, where the filter function is the dependent consumer, the signature (a -> Bool) of the function argument is the interface contract, the expression that uses the higher-order is the injector that, in this particular case, injects the implementation (\x -> (mod x 2) == 0) of the contract. More in general, can one relate higher-order functions and their usage pattern in functional programming to the dependency injection pattern in object-oriented languages? Or in the inverse direction, can dependency injection be compared to using some kind of higher-order function?

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  • What do you wish language designers paid attention to?

    - by Berin Loritsch
    The purpose of this question is not to assemble a laundry list of programming language features that you can't live without, or wish was in your main language of choice. The purpose of this question is to bring to light corners of languge design most language designers might not think about. So, instead of thinking about language feature X, think a little more philisophically. One of my biases, and perhaps it might be controversial, is that the softer side of engineering--the whys and what fors--are many times more important than the more concrete side. For example, Ruby was designed with a stated goal of improving developer happiness. While your opinions may be mixed on whether it delivered or not, the fact that was a goal means that some of the choices in language design were influenced by that philosophy. Please do not post: Syntax flame wars (I could care less whether you use whitespace [Python], keywords [Ruby], or curly braces [Java, C/C++, et. al.] to denote program blocks). That's just an implementation detail. "Any language that doesn't have feature X doesn't deserve to exist" type comments. There is at least one reason for all programming languages to exist--good or bad. Please do post: Philisophical ideas that language designers seem to miss. Technical concepts that seem to be poorly implemented more often than not. Please do provide an example of the pain it causes and if you have any ideas of how you would prefer it to function. Things you wish were in the platform's common library but seldom are. One the same token, things that usually are in a common library that you wish were not. Conceptual features such as built in test/assertion/contract/error handling support that you wish all programming languages would implement properly--and define properly. My hope is that this will be a fun and stimulating topic.

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  • Hobbyist transitioning to earn money on paid work?

    - by Chelonian
    I got into hobbyist Python programming some years ago on a whim, having never programmed before other than BASIC way back when, and little by little have cobbled together a, in my opinion, nice little desktop application that I might try to get out there in some fashion someday. It's roughly 15,000 logical lines of code, and includes use of Python, wxPython, SQLite, and a number of other libraries, works on Win and Linux (maybe Mac, untested) and I've gotten some good feedback about the application's virtues from non-programmer friends. I've also done a small application for data collection for animal behavior experiments, and an ad hoc tool to help generate a web page...and I've authored some tutorials. I consider my Python skills to be appreciably limited, my SQL skills to be very limited, but I'm not totally out to sea, either (e.g. I did FizzBuzz in a few minutes, did a "Monty Hall Dilemma" simulator in some minutes, etc.). I also put a strong premium on quality user experience; that is, the look and feel matters much to me and the software looks quite good, I feel. I know no other programming languages yet. I also know the basics of HTML/CSS (not considering them programming languages) and have created an artist's web page (that was described by a friend as "incredibly slick"...it's really not, though), and have a scientific background. I'm curious: Aside from directly selling my software, what's roughly possible--if anything--in terms of earning either side money on gigs, or actually getting hired at some level in the software industry, for someone with this general skill set?

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  • Do we ethically have the right to use the MAC Address for verification purposes?

    - by Matt Ridge
    I am writing a program, or starting at the very beginning of it, and I am thinking of purchase verification systems as a final step. I will be catering to Macs, PCs, and possibly Linux if all is said and done. I will also be programming this for smartphones as well using C++ and Objective-C. (I am writing a blueprint before going head first into it) That being said, I am not asking for help on doing it yet, but what I’m looking for is a realistic measurement for what could be expected as a viable and ethical option for purchase verification systems. Apple through the Apple Store, and some other stores out there have their own "You bought it" check. I am looking to use a three prong verification system. Email/password 16 to 32 character serial number using alpha/numeric and symbols with Upper and lowercase variants. MAC Address. The first two are in my mind ok, but I have to ask on an ethical standpoint, is a MAC Address to lock the software to said hardware unethical, or is it smart? I understand if an Ethernet card changes if not part of the logic board, or if the logic board changes so does the MAC address, so if that changes it will have to be re-verified, but I have to ask with how everything is today... Is it ethical to actually use the MAC address as a validation key or no? Should I be forward with this kind of verification system or should I keep it hidden as a secret? Yes I know hackers and others will find ways of knowing what I am doing, but in reality this is why I am asking. I know no verification is foolproof, but making it so that its harder to break is something I've always been interested in, and learning how to program is bringing up these questions, because I don't want to assume one thing and find out it's not really accepted in the programming world as a "you shouldn't do that" maneuver... Thanks in advance... I know this is my first programming question, but I am just learning how to program, and I am just making sure I'm not breaking some ethical programmer credo I shouldn't...

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  • How often do you review fundamentals?

    - by mlnyc
    So I've been out of school for a year and a half now. In school, of course we covered all the fundamentals: OS, databases, programming languages (i.e. syntax, binding rules, exception handling, recursion, etc), and fundamental algorithms. the rest were more in-depth topics on things like NLP, data mining, etc. Now, a year ago if you would have told me to write a quicksort, or reverse a singly-linked list, analyze the time complexity of this 'naive' algorithm vs it's dynamic programming counterpart, etc I would have been able to give you a decent and hopefully satisfying answer. But if you would have asked me more real world questions I might have been stumped (things like how would handle logging for an application, or security difference between GET and POST, differences between SQL Server and Oracle SQL, anything I list on my resume as currently working with [jQuery questions, ColdFusion questions, ...] etc) Now, I feel things are the opposite. I haven't wrote my own sort since graduating, and I don't really have to worry much about theoretical things that do not naturally fall into problems I am trying to solve. For example, I might give you some great SQL solutions using an analytical function that I would have otherwise been stumped on or write a cool web application using angular or something but ask me to write an algo for insertAfter(Element* elem) and I might not be able to do it in a reasonable time frame. I guess my question here to the experienced programmers is how do you balance the need to both learn and experiment with new technologies (fun!), working on personal projects (also fun!) working and solving real world problems in a timeboxed environment (so I might reach out to a library that does what I want rather than re-invent the wheel so that I can focus on the problem I am trying to solve) (work, basically), and refreshing on old theoretical material which is still valid for interviews and such (can be a drag)? Do you review older material (such as famous algorithms, dynamic programming, Big-O analysis, locking implementations) regularly or just when you need it? How much time do you dedicate to both in your 'deliberate practice' and do you have a certain to-do list of topics that you want to work on?

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  • What kinds of languages would be most useful for this kind of webapp?

    - by Caedar
    I've had some experience with programming in the past (2-3 years of C++ self-teaching), so I'm no stranger to the programming process, but there are so many languages out there that I'm lost when thinking about this project idea that's been floating around my head: I would like to create a webapp that would be used for helping somebody figure out what kinds of productivity tools would suit them. The first part of the app would basically be a survey with a variety of questions that would help weed out tools that wouldn't be useful for them. (Slider bar between minimalist and maximizer, slider bar between all free apps and no cost limit, checkboxes on what platforms are required, etc.) While the person is filling out the survey, they will see a web of applications, webapps, and other tools forming on the screen with links showing the relationships the programs have with eachother (syncing supported, good combinations of apps, etc.), along with a list of applications below sorted by general use (notetaking, document organization, storage, etc.) I would imagine that each program entered into the database that will be accessed would have a certain set of characteristics, ie. price, user friendliness, platforms supported, general uses, etc. and the survey would be designed to correlate to those elements and remove programs that don't match the criteria set. The difficult part of this entire process would be getting the web of applications to arrange itself and render properly. Now that I've finished mind-dumping, onto my question: What kinds/combinations of programming languages would you imagine being useful for this kind of project, and why? I learn best by setting up a project for myself like this one and tinkering with the languages, so I don't mind if the end product is out of reach from my current skill level. I'd just like some guidance so I don't fumble in the dark for too long.

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  • If you had to go back and re-learn your skill set, how would you do it?

    - by vorbb
    My younger brother is looking to start programming. He's 14, and technically-inclined, but no real experience programming. He's looking to me for guidance, and I don't feel as if my experience is enough, so I figured I'd ask here. He's more interested in web programming, but also has an interest in desktop/mobile/server applications. What would be a good learning path for him to take? I'm going to buy him a bunch of books for Christmas to get him started; the question is, what should he learn, and in which order? The way I see it, he needs to learn theory and code. I'd like to start him off with Python or Ruby or PHP. If he wants to get in to web, he's also going to need to learn HTML, CSS, Javascript, etc. Out of those three domains (Languages, Theory, Markup/Etc.), what is the best order do you think to learn in? Also, am I missing anything? Thanks!

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  • Programming doesn&rsquo;t have to be Magic

    - by Wes McClure
    In the show LOST, the Swan Station had a button that “had to be pushed” every 100 minutes to avoid disaster.  Several characters in the show took it upon themselves to have faith and religiously push the button, resetting the clock and averting the unknown “disaster”.  There are striking similarities in this story to the code we write every day.  Here are some common ones that I encounter: “I don’t know what it does but the application doesn’t work without it” “I added that code because I saw it in other similar places, I didn’t understand it, but thought it was necessary.” (for consistency, or to make things “work”) “An error message recommended it” “I copied that code” (and didn’t look at what it was doing) “It was suggested in a forum online and it fixed my problem so I left it” In all of these cases we haven’t done our due diligence to understand what the code we are writing is actually doing.  In the rush to get things done it seems like we’re willing to push any button (add any line of code) just to get our desired result and move on.  All of the above explanations are common things we encounter, and are valid ways to work through a problem we have, but when we find a solution to a task we are working on (whether a bug or a feature), we should take a moment to reflect on what we don’t understand.  Remove what isn’t necessary, comprehend and simplify what is.  Why is it detrimental to commit code we don’t understand? Perpetuates unnecessary code If you copy code that isn’t necessary, someone else is more likely to do so, especially peers Perpetuates tech debt Adding unnecessary code leads to extra code that must be understood, maintained and eventually cleaned up in longer lived projects Tech debt begets tech debt as other developers copy or use this code as guidelines in similar situations Increases maintenance How do we know the code is simplified if we don’t understand it? Perpetuates a lack of ownership Makes it seem ok to commit anything so long as it “gets the job done” Perpetuates the notion that programming is magic If we don’t take the time to understand every line of code we add, then we are contributing to the notion that it is simply enough to make the code work, regardless of how. TLDR Don’t commit code that you don’t understand, take the time to understand it, simplify it and then commit it!

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  • Programming Windows 8 Apps with HTML, CSS, and JavaScript - All you need in one title

    It took me a while to work through the 800+ pages of this title. And yes, I really mean working not reading... Since the release of Windows 8 it should be obvious to any Windows software developer that there are new ways to develop, deploy and market applications for a broader audience. Interestingly, Microsoft started to narrow the technological gap between the various platforms - desktop, web, smartphone and XBox - and development of modern apps with HTML, CSS and JavaScript couldn't be easier. Kraig covers all facets of modern Windows 8 apps from the basic building blocks and project templates in Visual Studio 2012 over to the thoughtful use of specific APIs to finally proper deployment in the App Store and potential monetization. The organisation of the book is lied out like step by step instructions or a tutorial. Kraig literally takes the reader by the hand and explains in detail in his examples about the reasons, the pros, and the cons of a certain way of implementation. Thanks to cross-references to other chapters he leaves the choice to the reader to dig deeper right now or to catch up at some time later. Personally, I have to admit that I really enjoyed the relaxed writing style. App development is not dust-dry rocket science and it should be joyful to learn about new technologies. And thanks to the richness of the various chapters and samples you could easily adapt and transfer the knowledge gained in this title to other platforms like Windows Phone 8. And last but not least: The ebook is freely available at Amazon, Microsoft Press and O'Reilly. Don't think about it, just get the book. Now. Update: I already mentioned this title in other blog entries which are related to Microsoft certification. Feel free to read on and to discover more online resources: Learning content for MCSDs: Web Applications and Windows Store Apps using HTML5 More content for MCSDs: Web Applications and Windows Store Apps using HTML5 O'Reilly offers free webcasts on their site, too. And in case that you would like to know more about Kraig's book and his experience with various development teams, please checkout this one: Zero to App in Two Weeks: Programming Windows 8 Apps in HTML, CSS, and JavaScript. The recording should be available soon.

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  • PC to USB transfer slow

    - by Vipin Ms
    I'm having trouble with USB transfer,not with external hard disk. Transfer starts with like, for the transfer of 700MB file it starts with 30mb/s and towards the end it stops at 0s and stays put for like 3-4 mins to transfer the last bit. I have tried different USB devices, but no luck. Is it a bug? Another important point is, in Kubuntu there is no such issue. So is it something related to Gnome? I'm using Ubuntu 11.10 64bit. Somebody please help, it's really annoying. Here are the details. PC all of my drives are in ext4. USB I tried ext3,ntfs and fat32. All having the same problem. Here are my USB controllers details: root@LAB:~# lspci|grep USB 00:1a.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 03) 00:1a.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 03) 00:1a.2 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 03) 00:1a.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 03) 00:1d.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 03) 00:1d.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 03) 00:1d.2 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 03) 00:1d.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 03) Here is an example of one transfer. I connected one of my 4GB usb device. Nov 24 12:01:25 LAB kernel: [ 1175.082175] userif-2: sent link up event. Nov 24 12:01:25 LAB kernel: [ 1695.684158] usb 2-2: new high speed USB device number 3 using ehci_hcd Nov 24 12:01:25 LAB mtp-probe: checking bus 2, device 3: "/sys/devices/pci0000:00/0000:00:1d.7/usb2/2-2" Nov 24 12:01:26 LAB mtp-probe: bus: 2, device: 3 was not an MTP device Nov 24 12:01:26 LAB kernel: [ 1696.132680] usbcore: registered new interface driver uas Nov 24 12:01:26 LAB kernel: [ 1696.142528] Initializing USB Mass Storage driver... Nov 24 12:01:26 LAB kernel: [ 1696.142919] scsi4 : usb-storage 2-2:1.0 Nov 24 12:01:26 LAB kernel: [ 1696.143146] usbcore: registered new interface driver usb-storage Nov 24 12:01:26 LAB kernel: [ 1696.143150] USB Mass Storage support registered. Nov 24 12:01:27 LAB kernel: [ 1697.141657] scsi 4:0:0:0: Direct-Access SanDisk U3 Cruzer Micro 8.02 PQ: 0 ANSI: 0 CCS Nov 24 12:01:27 LAB kernel: [ 1697.168827] sd 4:0:0:0: Attached scsi generic sg2 type 0 Nov 24 12:01:27 LAB kernel: [ 1697.169262] sd 4:0:0:0: [sdb] 7856127 512-byte logical blocks: (4.02 GB/3.74 GiB) Nov 24 12:01:27 LAB kernel: [ 1697.169762] sd 4:0:0:0: [sdb] Write Protect is off Nov 24 12:01:27 LAB kernel: [ 1697.169767] sd 4:0:0:0: [sdb] Mode Sense: 45 00 00 08 Nov 24 12:01:27 LAB kernel: [ 1697.171386] sd 4:0:0:0: [sdb] No Caching mode page present Nov 24 12:01:27 LAB kernel: [ 1697.171391] sd 4:0:0:0: [sdb] Assuming drive cache: write through Nov 24 12:01:27 LAB kernel: [ 1697.173503] sd 4:0:0:0: [sdb] No Caching mode page present Nov 24 12:01:27 LAB kernel: [ 1697.173510] sd 4:0:0:0: [sdb] Assuming drive cache: write through Nov 24 12:01:27 LAB kernel: [ 1697.175337] sdb: sdb1 After that I initiated one transfer. lsof -p 3575|tail -2 mv 3575 root 3r REG 8,8 1719599104 4325379 /media/Misc/The Tree of Life (2011) DVDRip XviD-MAXSPEED/The Tree of Life (2011) DVDRip XviD-MAXSPEED www.torentz.3xforum.ro.avi mv 3575 root 4w REG 8,17 1046347776 15 /media/SREE/The Tree of Life (2011) DVDRip XviD-MAXSPEED/The Tree of Life (2011) DVDRip XviD-MAXSPEED www.torentz.3xforum.ro.avi Here are the total time spent on that transfer. root@LAB:/media/SREE# time mv /media/Misc/The\ Tree\ of\ Life\ \(2011\)\ DVDRip\ XviD-MAXSPEED/ /media/SREE/ real 11m49.334s user 0m0.008s sys 0m5.260s root@LAB:/media/SREE# df -T|tail -2 /dev/sdb1 vfat 3918344 1679308 2239036 43% /media/SREE /dev/sda8 ext4 110110576 60096904 50013672 55% /media/Misc Do you think this is normal?? Approximately 12 minutes for 1.6Gb transfer? Thanks.

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  • Could spending time on Programmers.SE or Stack Overflow be substitute of good programming books for a non-beginner?

    - by Atul Goyal
    Could spending time (and actively participating) on Programmers.SE and Stack Overflow help me improve my programming skills any close to what spending time on reading a book like Code Complete 2 (which would otherwise be next in my reading list) will help. Ok, may be the answer to this question for someone who is beginning with programming might be a straight no, but I'd like to add that this question I'm asking in context when the person is familiar with programming languages but wants to improve his programming skills. I was reading this question on SO and also this book has been recommended by many others (including Jeff and Joel). To be more specific, I'd also add that even though I do programming in C, Java, Python,etc but still I'm not happy with my coding skills and reading the review of CC2 I realized I still need to improve a lot. So, basically I want to know what's the best way for me to improve programming skills - spend more time on here/SO or continue with CC2 and may be come here as and when time permits.

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  • How is programming affected by spatial aptitude?

    - by natli
    The longer I work on a project, the less clear it becomes. It's like I cannot seperate various classes/objects anymore in my head. Everything starts mixing up, and it's extremely hard to take it all apart again. I start putting functions in classes where they really don't belong, and make silly mistakes such as writing code that I later find was 100% obsolete; things are no longer clearly mappable in my head. It isn't until I take a step back for several hours (or days somtimes!) that I can actually see what's going on again, and be productive. I usually try to fight through this, I am so passionate about coding that I wouldn't for the life of me know what else I could be doing. This is when stuff can get really weird, I get so up in my head that I sort of lose touch with reality (to some extent) in that various actions, such as pouring a glass of water, no longer happen on a concious level. It happens on auto pilot, during which pretty much all of my concious concentration (is that even a thing?) is devoted to borderline pointless problem solving (trying to seperate elements of code). It feels like a losing battle. So I took an IQ test a while ago (Wechsler Adult Intelligence Scale I believe it was) and it turned out my Spatial Aptitude was quite low. I still got a decent score, just above average, so I won't have to poke things with a stick for a living, but I am a little worried that this is such a handicap when writing/engineering computer programs that I won't ever be able to do it seriously or professionally. I am very much interested in what other people think of this.. could a low spatial aptitude be the cause of the above described problems? Maybe I should be looking more along the lines of ADD or something similar, because I did get diagnosed with ADD at the age of 17 (5 years ago) but the medicine I received didn't seem to affect me that much so I never took it all that serious. Sorry if I got a little off topic there, I know this is not a mental help board, the question should be clear; How is programming affected by spatial aptitude? As far as I know people are born with low/med/high spatial aptitude, so I think it's interesting to find out if the more fortunate are better programmers by birth right.

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  • Should I continue to pursue programming based on my experience?

    - by El Be
    The reason I ask this question is because I am not sure my troubles come from a lack of confidence, or something much deeper like lack of passion. I'm hoping experienced programmers and developers can help identify the cause of my troubles. To be brief my undergraduate major was in Computer Science, but in a small school and I had the highest gpa in my year in computer science. The first time I ever programmed was once in the 5th grade (using logo) and when I was a freshman in college. I enjoyed programming when I was in school. Then I did an internships where I was expected to produce image processing software and program microchips. I was unsuccessful and produced little results and I hated the job, because I had to figure out everything for myself, did not have any help, and there was a lot of pressure to produce results. Although I tried I could not figure out what to do and was stuck all the time and made me dislike the job. When the internship ended I went to a PhD program for computer science at a prestigious computer science school. I had a very hard time with the course, met people who have been programming since they were 6 and made plenty of applications in their spare time (which I never did, although I tried). I even met many sophomores who understood more than I did. The combination of this and other things have made me feel that programming is not for me, but sometimes I consider a career in programming. I still consider programming as a career because of the career potential (not only just because of money). Based on my experience do you believe my confidence has just been shaken and I should continue to prepare for a programming career, or do you see a lack of passion and it would make it tough to continue programming. thank you for reading and for your advice Thank you for everyone's advice so far! Also: I dropped out of the ph.D program for computer science and switched to a master's in computer graphics. Its more applied, but I still find it hard to be motivated (due to either lack of confidence or passion), but since programming is such a big field I am looking for that niche area that I feel good programming in.

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  • Kernel Panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) after apt-get upgrade

    - by Edward
    I'm using Ubuntu 9.1 server edition, I get this error during boot time after I ran sudo apt-get upgrade when checking my kernel version, uname -r returns 2.6.31-14-generic but when i run dpkg -l 'linux-image*' | grep ^.i I cannot find 2.6.31-14 (only contains 2.6.32*) Following the solution in the thread: Kernel Panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) doesn't work for me I'm running the commands inside the Rescue mode by booting from the Ubuntu 9.1 Installation Disc Do I need to update my kernel and run update-initramfs + update-grub again? If so, how can I update the kernel? apt-get install any linux-headers/image cannot change the uname -r value Thanks!

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  • Can realtek 8192cu usb wireless card be used in ubuntu 12.04 with kernel 3.2.0?

    - by waterloo2005
    I do like the post RTL8188CUS Wireless USB Dongle doesn't work unless I disable wireless security . But when I plug my 8192cu usb wireless card, my computer screen is off. At that time I even can not use Alt SysRq k or Alt SysRq + reisub. I compile the latest driver of 8192cu on ubuntu 12.04 with kernel 3.2.0-34. In RealTek site, I download 8192cu drive which is for Linux Kernel 2.6.18~2.6.38 and Kernel 3.0.8. But now in Ubuntu12.04 my kernel is 3.2.0-34. Every time I plug the usb 8192cu wireless card my system halts. Now I try to blacklist both the system's rtl8192cu driver and the new 8192cu driver I compile, but the system still halts when I plug the usb driver. What about you ? Thanks!

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  • Flush kernel's TCP buffer with `MSG_MORE`-flagged packets

    - by timn
    send()'s man page reveals the MSG_MORE flag which is asserted to act like TCP_CORK. I have a wrapper function around send(): int SocketConnection_Write(SocketConnection *this, void *buf, int len) { errno = 0; int sent = send(this->fd, buf, len, MSG_NOSIGNAL); if (errno == EPIPE || errno == ENOTCONN) { throw(exc, &SocketConnection_NotConnectedException); } else if (errno == ECONNRESET) { throw(exc, &SocketConnection_ConnectionResetException); } else if (sent != len) { throw(exc, &SocketConnection_LengthMismatchException); } return sent; } Assuming I want to use the kernel buffer, I could go with TCP_CORK, enable whenever it is necessary and then disable it to flush the buffer. But on the other hand, thereby the need for an additional system call arises. Thus, the usage of MSG_MORE seems more appropriate to me. I'd simply change the above send() line to: int sent = send(this->fd, buf, len, MSG_NOSIGNAL | MSG_MORE); According to lwm.net, packets will be flushed automatically if they are large enough: If an application sets that option on a socket, the kernel will not send out short packets. Instead, it will wait until enough data has shown up to fill a maximum-size packet, then send it. When TCP_CORK is turned off, any remaining data will go out on the wire. But this section only refers to TCP_CORK. Now, what is the proper way to flush MSG_MORE packets? I can only think of two possibilities: Call send() with an empty buffer and without MSG_MORE being set Re-apply the TCP_CORK option as described on this page Unfortunately the whole topic is very poorly documented and I couldn't find much on the Internet. I am also wondering how to check that everything works as expected? Obviously running the server through strace' is not an option. So the only simplest way would be to usenetcat' and then look at its `strace' output? Or will the kernel handle traffic differently transmitted over a loopback interface?

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  • My kernel only works in block (0,0)

    - by ZeroDivide
    I am trying to write a simple matrixMultiplication application that multiplies two square matrices using CUDA. I am having a problem where my kernel is only computing correctly in block (0,0) of the grid. This is my invocation code: dim3 dimBlock(4,4,1); dim3 dimGrid(4,4,1); //Launch the kernel; MatrixMulKernel<<<dimGrid,dimBlock>>>(Md,Nd,Pd,Width); This is my Kernel function __global__ void MatrixMulKernel(int* Md, int* Nd, int* Pd, int Width) { const int tx = threadIdx.x; const int ty = threadIdx.y; const int bx = blockIdx.x; const int by = blockIdx.y; const int row = (by * blockDim.y + ty); const int col = (bx * blockDim.x + tx); //Pvalue stores the Pd element that is computed by the thread int Pvalue = 0; for (int k = 0; k < Width; k++) { Pvalue += Md[row * Width + k] * Nd[k * Width + col]; } __syncthreads(); //Write the matrix to device memory each thread writes one element Pd[row * Width + col] = Pvalue; } I think the problem may have something to do with memory but I'm a bit lost. What should I do to make this code work across several blocks?

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  • Using a 64bit Linux kernel, can't see more than 4GB of RAM in /proc/meminfo

    - by Chris Huang-Leaver
    I'm running my new computer which has 8GB of RAM installed, which is visable from BIOS page, does not show in /proc/meminfo uname -a Linux localhost 3.0.6-gentoo #2 SMP PREEMPT Sat Nov 19 10:45:22 GMT-- x86_64 AMD Phenom(tm) II X4 955 Processor AuthenticAMD GNU/Linux The result of /proc/meminfo is as follows: (thans Andrey) MemTotal: 4021348 kB MemFree: 1440280 kB Buffers: 23696 kB Cached: 1710828 kB SwapCached: 4956 kB Active: 1389904 kB Inactive: 841364 kB Active(anon): 1337812 kB Inactive(anon): 714060 kB Active(file): 52092 kB Inactive(file): 127304 kB Unevictable: 32 kB Mlocked: 32 kB SwapTotal: 8388604 kB SwapFree: 8047900 kB Dirty: 0 kB Writeback: 0 kB AnonPages: 492732 kB Mapped: 47528 kB Shmem: 1555120 kB Slab: 267724 kB SReclaimable: 177464 kB SUnreclaim: 90260 kB KernelStack: 1176 kB PageTables: 12148 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 10399276 kB Committed_AS: 3293896 kB VmallocTotal: 34359738367 kB VmallocUsed: 317008 kB VmallocChunk: 34359398908 kB AnonHugePages: 120832 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 23552 kB DirectMap2M: 3088384 kB DirectMap1G: 1048576 kB I have tried using mem=8G as a kernel boot parameter, I read a post about setting HIGHMEM64G to yes, before realising that only applies to 32bit kernels. Trying dmindecode -t memory SMBIOS 2.7 present. Handle 0x0026, DMI type 16, 23 bytes Physical Memory Array Location: System Board Or Motherboard Use: System Memory Error Correction Type: Multi-bit ECC Maximum Capacity: 32 GB Error Information Handle: Not Provided Number Of Devices: 4 Handle 0x0028, DMI type 17, 34 bytes Memory Device Array Handle: 0x0026 Error Information Handle: Not Provided Total Width: 64 bits Data Width: 64 bits Size: 4096 MB Form Factor: DIMM Set: None Locator: DIMM0 Bank Locator: BANK0 Type: <OUT OF SPEC> Type Detail: Synchronous Speed: 1333 MHz Manufacturer: Manufacturer0 Serial Number: SerNum0 Asset Tag: AssetTagNum0 Part Number: Array1_PartNumber0 Rank: Unknown Handle 0x002A, DMI type 17, 34 bytes Memory Device Array Handle: 0x0026 Error Information Handle: Not Provided Total Width: Unknown Data Width: 64 bits Size: No Module Installed Form Factor: DIMM Set: None Locator: DIMM1 Bank Locator: BANK1 Type: Unknown Type Detail: Synchronous Speed: Unknown Manufacturer: Manufacturer1 Serial Number: SerNum1 Asset Tag: AssetTagNum1 Part Number: Array1_PartNumber1 Rank: Unknown Handle 0x002C, DMI type 17, 34 bytes Memory Device Array Handle: 0x0026 Error Information Handle: Not Provided Total Width: 64 bits Data Width: 64 bits Size: 4096 MB Form Factor: DIMM Set: None Locator: DIMM2 Bank Locator: BANK2 Type: <OUT OF SPEC> Type Detail: Synchronous Speed: 1333 MHz Manufacturer: Manufacturer2 Serial Number: SerNum2 Asset Tag: AssetTagNum2 Part Number: Array1_PartNumber2 Rank: Unknown Handle 0x002E, DMI type 17, 34 bytes Memory Device Array Handle: 0x0026 Error Information Handle: Not Provided Total Width: Unknown Data Width: 64 bits Size: No Module Installed Form Factor: DIMM Set: None Locator: DIMM3 Bank Locator: BANK3 Type: Unknown Type Detail: Synchronous Speed: Unknown Manufacturer: Manufacturer3 Serial Number: SerNum3 Asset Tag: AssetTagNum3 Part Number: Array1_PartNumber3 Rank: Unknown

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  • iotop for Linux kernel 2.6.18

    - by Lightsauce
    So it has to come to my attention that iotop isn't availalbe for 2.6.18 since it's less than 2.6.20 and requires Python 2.6+. I've done some research and came across this article: http://lserinol.blogspot.com/2009/09/io-usage-per-process-on-linux.html According to this, if these process have io stats in /proc/pid#/io (where pid# is the process #) it's doable regardless of the kernel version. So, in reality, I could upgrade Python to 2.6 and test out iotop. However, my flavor of Linux, CentOS release 5.5 (Final), only supports Python 2.4.3-44.el5 currently. If I were to do uninstall from yum, it doesn't look so pretty. It ends up wanting to uninstall 235 packages, most of which are very important! I read in one place, online (I forget the URL from yesterday), that you can install Python 2.6+ parallel to this one, and have the rpm install for iotop use that. Well, I didn't choose that route. I figured, what the heck, lets write iotop (not copying it, but reverse engineering it without actually looking at it's code/it in use) in bash. I thought it would just grab the /proc/pid#/io file and parse stats. So I wrote a script to grab the top 10 rchar, wchar, read_bytes, and write_bytes by collecting all these stats from all the /proc/pid#/io files, sorting them by each metric, then grabbing the top 10 highest values. The conclusion, the data seems completely useless. Does anybody know any resources for advanced Linux where I can figure out how to take these /proc/pid#/ directories and figure out what the heck they are doing with io on the disk? My main goal is to figure out what exactly is causing high load on my disk. I just know it's on the / partition (/dev/sda2 in this case), and I'm not really sure how to narrow it down without the help of iotop. If I run iostat to grab metrics for 1 minute, every second, the first result it gives me shows a high 'kB_read/s', so that makes me think, it's reading mostly. However, if I watch the update it gives me every second, it's actually just showing values for kB_wrtn/s. This makes me think the initial value iostat gives me is misleading.

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  • How can we improve overall Programmer Education & Training?

    - by crosenblum
    Last week, I was just viewing this amazing interview by Kevin Rose of Phillip Rosedale, of Second Life. And they had an amazing discussion about how to find, hire and identify good programmer's, and how hard it is to find good ones. Which has lead me to really think about the way we programmer's learn, are taught. For a majority of us, myself included, we are self-taught. Which is great about being a programmer, anyone can learn and develop skills. But this also means, that there is no real standards of what a good programmer is/are, and what kind of environment's encourage the growth of programming skills. This isn't so much a question, but just a desire in me, to see how we can change the culture of programming, and the manager's of programming, so that education and self-improvement is encouraged. There are a lot of avenue's for continued education, youtube videos, books, conferences, but because of the experiental nature of what we do, it isn't always clear what's important to learn and to master. Let's look at the The Joel 12 Steps. The Joel Test Do you use source control? Can you make a build in one step? Do you make daily builds? Do you have a bug database? Do you fix bugs before writing new code? Do you have an up-to-date schedule? Do you have a spec? Do programmers have quiet working conditions? Do you use the best tools money can buy? Do you have testers? Do new candidates write code during their interview? Do you do hallway usability testing? I think all of these have important value, but because of something I call the Experiential Gap, if a programmer or manager has never experienced any of the negative consequences for not having done items on the list, they will never see the need to do any of them. The Experiental Gap, is my basic theory, that each of us has different jobs and different experiences. So for some of us, that have always worked with dozens of programmer's, source control is a must have. But for people who have always been the only programmer, they can not imagine the need for source control. And it's because of this major flaw in how we learn, that we evaluate people by what best practices they do or not do, and the reason for either can start a flame war. We always evaluate people in our field by what they do, and think "Oh if this guy/gal isn't doing xyz best practice, he/she can't be a good programmer, so let's not waste time or energy talking to them." This is exactly why we have so many programming flame wars, that it becomes, because of the Experiental Gap, we can't imagine people not having made the decisions that we have had to made. So this has lead me to think, that we totally need to rethink how we train, educate and manage programmer's. For example, what percentage of you have had encouragement by your manager's to go to conferences, and even have them pay for it? For me, and a lot of people, this is extremely rare, a lot of us would love to go to conferences, to learn more, but the money ain't there to do that. So the point of this question is really to spark a lot of how can we train, learn and manage better? How can we create a new culture of learning that doesn't insult people for not having the same job experiences. Yes we all have jobs and work to do, but our ability to do our jobs well, depends on our desire, interest and support in improving our mastery of our skills. Right now, I see our culture being rather disorganized, we support the elite, but those tons of us that want to get better, just don't have enough support to learn and improve ourselves. I mean, do we as an industry, want to be perceived as just replaceable cogs? Thank you...

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  • Collision between sprites in game programming?

    - by Lyn Maxino
    I've since just started coding for an android game using eclipse. I've read Beginning Android Game Programming and various other e-books. Recently, I've encountered a problem with collision between sprites. I've used this code template for my program. package com.project.CAI_test; import java.util.Random; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Rect; public class Sprite { // direction = 0 up, 1 left, 2 down, 3 right, // animation = 3 back, 1 left, 0 front, 2 right int[] DIRECTION_TO_ANIMATION_MAP = { 3, 1, 0, 2 }; private static final int BMP_ROWS = 4; private static final int BMP_COLUMNS = 3; private static final int MAX_SPEED = 5; private GameView gameView; private Bitmap bmp; private int x = 0; private int y = 0; private int xSpeed; private int ySpeed; private int currentFrame = 0; private int width; private int height; public Sprite(GameView gameView, Bitmap bmp) { this.width = bmp.getWidth() / BMP_COLUMNS; this.height = bmp.getHeight() / BMP_ROWS; this.gameView = gameView; this.bmp = bmp; Random rnd = new Random(); x = rnd.nextInt(gameView.getWidth() - width); y = rnd.nextInt(gameView.getHeight() - height); xSpeed = rnd.nextInt(MAX_SPEED * 2) - MAX_SPEED; ySpeed = rnd.nextInt(MAX_SPEED * 2) - MAX_SPEED; } private void update() { if (x >= gameView.getWidth() - width - xSpeed || x + xSpeed <= 0) { xSpeed = -xSpeed; } x = x + xSpeed; if (y >= gameView.getHeight() - height - ySpeed || y + ySpeed <= 0) { ySpeed = -ySpeed; } y = y + ySpeed; currentFrame = ++currentFrame % BMP_COLUMNS; } public void onDraw(Canvas canvas) { update(); int srcX = currentFrame * width; int srcY = getAnimationRow() * height; Rect src = new Rect(srcX, srcY, srcX + width, srcY + height); Rect dst = new Rect(x, y, x + width, y + height); canvas.drawBitmap(bmp, src, dst, null); } private int getAnimationRow() { double dirDouble = (Math.atan2(xSpeed, ySpeed) / (Math.PI / 2) + 2); int direction = (int) Math.round(dirDouble) % BMP_ROWS; return DIRECTION_TO_ANIMATION_MAP[direction]; } public boolean isCollition(float x2, float y2) { return x2 > x && x2 < x + width && y2 > y && y2 < y + height; } } The above code only detects collision between the generated sprites and the surface border. What I want to achieve is a collision detection that is controlled by the update function without having to change much of the coding. Probably several lines placed in the update() function. Tnx for any comment/suggestion.

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  • Reading graph inputs for a programming puzzle and then solving it

    - by Vrashabh
    I just took a programming competition question and I absolutely bombed it. I had trouble right at the beginning itself from reading the input set. The question was basically a variant of this puzzle http://codercharts.com/puzzle/evacuation-plan but also had an hour component in the first line(say 3 hours after start of evacuation). It reads like this This puzzle is a tribute to all the people who suffered from the earthquake in Japan. The goal of this puzzle is, given a network of road and locations, to determine the maximum number of people that can be evacuated. The people must be evacuated from evacuation points to rescue points. The list of road and the number of people they can carry per hour is provided. Input Specifications Your program must accept one and only one command line argument: the input file. The input file is formatted as follows: the first line contains 4 integers n r s t n is the number of locations (each location is given by a number from 0 to n-1) r is the number of roads s is the number of locations to be evacuated from (evacuation points) t is the number of locations where people must be evacuated to (rescue points) the second line contains s integers giving the locations of the evacuation points the third line contains t integers giving the locations of the rescue points the r following lines contain to the road definitions. Each road is defined by 3 integers l1 l2 width where l1 and l2 are the locations connected by the road (roads are one-way) and width is the number of people per hour that can fit on the road Now look at the sample input set 5 5 1 2 3 0 3 4 0 1 10 0 2 5 1 2 4 1 3 5 2 4 10 The 3 in the first line is the additional component and is defined as the number of hours since the resuce has started which is 3 in this case. Now my solution was to use Dijisktras algorithm to find the shortest path between each of the rescue and evac nodes. Now my problem started with how to read the input set. I read the first line in python and stored the values in variables. But then I did not know how to store the values of the distance between the nodes and what DS to use and how to input it to say a standard implementation of dijikstras algorithm. So my question is two fold 1.) How do I take the input of such problems? - I have faced this problem in quite a few competitions recently and I hope I can get a simple code snippet or an explanation in java or python to read the data input set in such a way that I can input it as a graph to graph algorithms like dijikstra and floyd/warshall. Also a solution to the above problem would also help. 2.) How to solve this puzzle? My algorithm was: Find shortest path between evac points (in the above example it is 14 from 0 to 3) Multiply it by number of hours to get maximal number of saves Also the answer given for the variant for the input set was 24 which I dont understand. Can someone explain that also. UPDATE: I get how the answer is 14 in the given problem link - it seems to be just the shortest path between node 0 and 3. But with the 3 hour component how is the answer 24 UPDATE I get how it is 24 - its a complete graph traversal at every hour and this is how I solve it Hour 1 Node 0 to Node 1 - 10 people Node 0 to Node 2- 5 people TotalRescueCount=0 Node 1=10 Node 2= 5 Hour 2 Node 1 to Node 3 = 5(Rescued) Node 2 to Node 4 = 5(Rescued) Node 0 to Node 1 = 10 Node 0 to Node 2 = 5 Node 1 to Node 2 = 4 TotalRescueCount = 10 Node 1 = 10 Node 2= 5+4 = 9 Hour 3 Node 1 to Node 3 = 5(Rescued) Node 2 to Node 4 = 5+4 = 9(Rescued) TotalRescueCount = 9+5+10 = 24 It hard enough for this case , for multiple evac and rescue points how in the world would I write a pgm for this ?

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