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• What are the advantages of programming to under an OS as opposed to bare metal executive?

  - by gby

  Assume you are presented with an embedded system application to program, in C, on a multi-core environment (think a Cavium or Tilera) and need to choose between two environments: Code the application under Linux in SMP mode or code the application under a thin bare metal executive (something like a very minimal RTOS), perhaps with a single core running UP Linux that can serve control tasks. For the purpose of this question, assume that both environment provide the same level of performance guarantees in any measurable aspects of run time performance, including number of meaningful action per second, jitter, latency, real time considerations - the works. (and yes, I realize this is by far not a trivial assumption at all, bare with me). How would you justify going with a Linux SMP based solution rather then a bare metal thin executive solution? The question may seems silly. It certainly seems obvious to me - but I have to convince someone that does not think the same. Could you help make a list of arguments in favor of choosing a real SMP aware OS (Linux) vs. a bare metal executive assuming performance guarantees are NOT an issue? Many thanks

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• RPi and Java Embedded GPIO: Java code to blink more LEDs

  - by hinkmond

  Now, it's time to blink the other GPIO ports with the other LEDs connected to them. This is easy using Java Embedded, since the Java programming language is powerful and flexible. Embedded developers are not used to this, since the C programming language is more popular but less easy to develop in. We just need to use a dynamic Java String array to map to the pinouts of the GPIO port names from the previous diagram posted. This way we can address each "channel" with an index into that String array. static String[] GpioChannels = { "0", "1", "4", "17", "21", "22", "10", "9" }; With this new dynamic array, we can streamline the main() of this Java program to activate all the ports. /** * @param args the command line arguments */ public static void main(String[] args) { FileWriter[] commandChannels; try { /*** Init GPIO port for output ***/ // Open file handles to GPIO port unexport and export controls FileWriter unexportFile = new FileWriter("/sys/class/gpio/unexport"); FileWriter exportFile = new FileWriter("/sys/class/gpio/export"); for (String gpioChannel : GpioChannels) { System.out.println(gpioChannel); // Reset the port unexportFile.write(gpioChannel); unexportFile.flush(); // Set the port for use exportFile.write(gpioChannel); exportFile.flush(); // Open file handle to port input/output control FileWriter directionFile = new FileWriter("/sys/class/gpio/gpio" + gpioChannel + "/direction"); // Set port for output directionFile.write(GPIO_OUT); directionFile.flush(); } And, then simply add array code to where we blink the LED to make it blink all the LEDS on and off at once. /*** Send commands to GPIO port ***/ commandChannels = new FileWriter[GpioChannels.length]; for (int channum=0; channum It's easier than falling off a log... or at least easier than C programming. Hinkmond

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• Sucking Less Every Year?

  - by AdityaGameProgrammer

  Sucking Less Every Year -Jeff Atwood I had come across this insightful article.Quoting directly from the post I've often thought that sucking less every year is how humble programmers improve. You should be unhappy with code you wrote a year ago. If you aren't, that means either A) you haven't learned anything in a year, B) your code can't be improved, or C) you never revisit old code. All of these are the kiss of death for software developers. How often does this happen or not happen to you? How long before you see an actual improvement in your coding ? month, year? Do you ever revisit Your old code? How often does your old code plague you? or how often do you have to deal with your technical debt. It is definitely very painful to fix old bugs n dirty code that we may have done to quickly meet a deadline and those quick fixes ,some cases we may have to rewrite most of the application/code. No arguments about that. Some of the developers i had come across argued that they were already at the evolved stage where their coding doesn't need improvement or cant get improved anymore. Does this happen? If so how many years into coding on a particular language does one expect this to happen? Related: Ever look back at some of your old code and grimace in pain? Star Wars Moment in Code "Luke! I am your code!" "No! Impossible! It can't be!"

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• How do I disable all lid close processes?

  - by Mat

  I want to be able to close my laptop without Ubuntu registering it. I've been looking everywhere and I've found plenty of people with the same problem but no real solutions. Obviously I have set the lid close setting to 'do nothing' for both AC and battery, but when I close the lid it still blanks the screen, disconnects from external monitors, and brings up the lock screen when I reopen it. Some people have suggested disabling the lock screen, but this doesn't stop the screen blanking and external displays disconnecting, and I don't want to disable the lock anyway, as I still want it when I tell Ubuntu to lock or sleep or whatever else. Others have suggested it's something to do with ACPI support, but I have tried changing some ACPI scripts, and even removed them completely (e.g. /etc/acpi/lid.sh and /etc/acpi/events/lidbtn) and it makes no difference. There must be a bit of code somewhere that can just be removed or commented out or altered to prevent any lid close actions - does anyone know where? I know this has been asked before, but I'm getting really frustrated with this problem. I'm disappointed to say that I'm actually using Windows 7 more often just because it's quite happy to completely ignore the closed lid. So I just wanted to check, are we any closer to a real solution for this problem?

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• Performing client-side OAuth authorized Twitter API calls versus server side, how much of a difference is there in terms of performance?

  - by Terence Ponce

  I'm working on a Twitter application in Ruby on Rails. One of the biggest arguments that I have with other people on the project is the method of calling the Twitter API. Before, everything was done on the server: OAuth login, updating the user's Twitter data, and retrieving tweets. Retrieving tweets was the heaviest thing to do since we don't store the tweets in our database, so viewing the tweets means that we have to call the API every time. One of the people in the project suggested that we call the tweets through Javascript instead to lessen the load on the server. We used GET search, which, correct me if I'm wrong, will be removed when v1.0 becomes completely deprecated, but that really isn't a concern now. When the Twitter API has migrated completely to v1.1 (again, correct me if I'm wrong), every calls to the API must be authenticated, so we have to authenticate our Javascript requests to the API. As said here: We don't support or recommend performing OAuth directly through Javascript -- it's insecure and puts your application at risk. The only acceptable way to perform it is if you kept all keys and secrets server-side, computed the OAuth signatures and parameters server side, then issued the request client-side from the server-generated OAuth values. If we do exactly what Twitter suggests, the only difference between this and doing everything server-side is that our server won't have to contact the Twitter API anymore every time the user wants to view tweets. Here's how I would picture what's happening every time the user makes a request: If we do it through Javascript, it would be harder on my part because I would have to create the signatures manually for every request, but I will gladly do it if the boost in performance is worth all the trouble. Doing it through Ruby on Rails would be very easy since the Twitter gem does most of the grunt work already, so I'm really encouraging the other people in the project to agree with me. Is the difference in performance trivial or is it significant enough to switch to Javascript?

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• Can I set my Optimus Nvidia card to run Unity3D with bumblebee?

  - by manuhalo

  I'd like to know whether I can run compiz on my Nvidia card to speed things up. It's a Dell XPS15 laptop but I'm mostly using it as a desktop, so battery life is not important. Apparently my Intel integrated card is able to run unity 3D, but my Nvidia GT 420M is not. Here's the output of unity_support_test, both with optirun and without it: manuhalo@Ubuntu-XPS-L501X:~$ optirun /usr/lib/nux/unity_support_test -p OpenGL vendor string: NVIDIA Corporation OpenGL renderer string: GeForce GT 420M/PCI/SSE2 OpenGL version string: 4.1.0 NVIDIA 280.13 Not software rendered: yes Not blacklisted: yes GLX fbconfig: yes GLX texture from pixmap: no GL npot or rect textures: yes GL vertex program: yes GL fragment program: yes GL vertex buffer object: yes GL framebuffer object: yes GL version is 1.4+: yes Unity 3D supported: no manuhalo@Ubuntu-XPS-L501X:~$ /usr/lib/nux/unity_support_test -p OpenGL vendor string: Tungsten Graphics, Inc OpenGL renderer string: Mesa DRI Intel(R) Ironlake Mobile OpenGL version string: 2.1 Mesa 7.11 Not software rendered: yes Not blacklisted: yes GLX fbconfig: yes GLX texture from pixmap: yes GL npot or rect textures: yes GL vertex program: yes GL fragment program: yes GL vertex buffer object: yes GL framebuffer object: yes GL version is 1.4+: yes Unity 3D supported: yes Any ideas of why this is happening? Thanks in advance to anyone able to shed some light on this. What I have tried: Installed the v290 drivers from the x-stable PPA. Tried forcing Unity-3D to work by telling Unity to ignore the unity-support-test results i.e. gksudo gedit /etc/environment add the following UNITY_FORCE_START=1 to the end of the file.

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• Tender vs. Requirements vs. Solution Design

  - by Tom Tom

  Conventionally, which of the above documents is deemed to hold the most weight when it comes to system acceptance? I recently had a conversation along these lines: It was argued that the initial requirements / tender documentation should be used to determine system acceptance. It was said that the solution design only serves to describe the way in which the system will solve the problem, not the problem it will solve. Furthermore, it was argued that if requirements are missed during solution design, the requirements should be referenced during system acceptance and that if any requirements were missed then the original tender should be referenced. Conversely, I suggested that - while requirements may be based on the original tender - they supersede it once agreed with the stakeholders. Furthermore, during solution design, analysis is performed to address and refine these initial requirements, translating them into a system capable of meeting the actual requirements. Once signed off by the relevant users, this solution design should absolutely represent the requirements (by virtue of the fact that it's designed upon them) but actually supersedes them as the basis for system acceptance. Is one of the above arguments more valid than the other?

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• CodePlex Daily Summary for Monday, October 21, 2013

  CodePlex Daily Summary for Monday, October 21, 2013Popular ReleasesVirtual Wifi Hotspot for Windows 7 & 8: Virtual Router Plus 2.6.0: Virtual Router Plus 2.6.0Fast YouTube Downloader: Fast YouTube Downloader 2.3.0: Fast YouTube DownloaderABCat: ABCat v.2.0a: ?????? ????? ??? ????????? ????????????. ???????? ???, ?? ?? ????? ???? :) ?? ??????? ??????????? ???????? ?? Windows 7 - ????? ??????? ????????? ?? ???? ??? ?????? ??????.Magick.NET: Magick.NET 6.8.7.101: Magick.NET linked with ImageMagick 6.8.7.1. Breaking changes: - Renamed Matrix classes: MatrixColor = ColorMatrix and MatrixConvolve = ConvolveMatrix. - Renamed Depth method with Channels parameter to BitDepth and changed the other method into a property.VidCoder: 1.5.9 Beta: Added Rip DVD and Rip Blu-ray AutoPlay actions for Windows: now you can have VidCoder start up and scan a disc when you insert it. Go to Start -> AutoPlay to set it up. Added error message for Windows XP users rather than letting it crash. Removed "quality" preset from list for QSV as it currently doesn't offer much improvement. Changed installer to ignore version number when copying files over. Should reduce the chances of a bug from me forgetting to increment a version number. Fixed ...MSBuild Extension Pack: October 2013: Release Blog Post The MSBuild Extension Pack October 2013 release provides a collection of over 480 MSBuild tasks. A high level summary of what the tasks currently cover includes the following: System Items: Active Directory, Certificates, COM+, Console, Date and Time, Drives, Environment Variables, Event Logs, Files and Folders, FTP, GAC, Network, Performance Counters, Registry, Services, Sound Code: Assemblies, AsyncExec, CAB Files, Code Signing, DynamicExecute, File Detokenisation, GUI...VG-Ripper & PG-Ripper: VG-Ripper 2.9.49: changes NEW: Added Support for "ImageTeam.org links NEW: Added Support for "ImgNext.com" links NEW: Added Support for "HostUrImage.com" links NEW: Added Support for "3XVintage.com" linksMedia Companion: Media Companion MC3.583b: As before release but fixed for no movie poster sourcesNew* Both - Added 'An' as option to ignore in title * Movie - Renaming - added %Z - Sorttitle to Legend * Movie - Renaming - added %O - Audio Channels to Legend * Movie - Remove a poster source from priority list. Reset List back to defaults. * Made Media Companion truly portable application. Fixed* Movie - browse for Poster Or Fanart, allows for jpg, tbn, png and bmp images * Movie - Alt Fanart Browser - Url or Browse window now fully...MoreTerra (Terraria World Viewer): MoreTerra 1.11.3.1: Release 1.11.3.1 ================ = New Features = ================ Added markers for Copper Cache, Silver Cache and the Enchanted Sword. ============= = Bug Fixes = ============= Use Official Colors now no longer tries to change the Draw Wires option instead. World reading was breaking for people with a stock 1.2 Terraria version. Changed world name reading so it does not crash the program if you load MoreTerra while Terraria is saving the world. =================== = Feature Removal = =...patterns & practices - Windows Azure Guidance: Cloud Design Patterns: 1st drop of Cloud Design Patterns project. It contains 14 patterns with 6 related guidance.Player Framework by Microsoft: Player Framework for Windows and WP (v1.3): Includes all changes in v1.3 beta 1 and v1.3 beta 2 Support for Windows 8.1 RTM and VS2013 RTM Xaml: New property: AutoLoadPluginTypes to help control which stock plugins are loaded by default (requires AutoLoadPlugins = true). Support for SystemMediaTransportControls on Windows 8.1 JS: Support for visual markers in the timeline. JS: Support for markers collection and markerreached event. JS: New ChaptersPlugin to automatically populate timeline with chapter tracks. JS: Audio an...Json.NET: Json.NET 5.0 Release 8: Fix - Fixed not writing string quotes when QuoteName is falsePowerShell Community Extensions: 3.1 Production: PowerShell Community Extensions 3.1 Release NotesOct 17, 2013 This version of PSCX supports Windows PowerShell 3.0 and 4.0 See the ReleaseNotes.txt download above for more information.SQL Power Doc: Version 1.0.2.1: Misc. bug fixes Added logic to resolve members of a Windows Group server login Added columns to Excel workbooks to show definitions for server permissions, server roles, database permissions, and database rolesSocial Network Importer for NodeXL: SocialNetImporter(v.1.9): This new version includes: - Download latest status update and use it as vertex tooltip - Limit the timelines to parse to me, my friends or both - Fixed some reported bugs about the fan page and group importer - Fixed the login bug reported latelyTerrariViewer: TerrariViewer v7.1 [Terraria Inventory Editor]: You can now backspace in number fields Items added in 1.2.0.3 no longer corrupt player files Buff durations capped at 9999999 Item stacks capped at 9999999 Version info added Prefix IDs corrected Shoe and Eye color box are now properly clickable Moved Bank and Safe into their own tab Users will now be notified of new updatesPython Tools for Visual Studio: 2.0: PTVS 2.0 We’re pleased to announce the release of Python Tools for Visual Studio 2.0 RTM. Python Tools for Visual Studio (PTVS) is an open-source plug-in for Visual Studio which supports programming with the Python language. PTVS supports a broad range of features including CPython/IronPython, Edit/Intellisense/Debug/Profile, Cloud, IPython, and cross platform and cross language debugging support. QUICK VIDEO OVERVIEW For a quick overview of the general IDE experience, please watch this v...LINQ to Twitter: LINQ to Twitter v2.1.09: Supports .NET 3.5, .NET 4.0, .NET 4.5, Silverlight 4.0, Windows Phone 7.1, Windows Phone 8, Client Profile, Windows 8, and Windows Azure. 100% Twitter API coverage. Also supports Twitter API v1.1! Also on NuGet.Sandcastle Help File Builder: SHFB v1.9.8.0 with Visual Studio Package: General InformationIMPORTANT: On some systems, the content of the ZIP file is blocked and the installer may fail to run. Before extracting it, right click on the ZIP file, select Properties, and click on the Unblock button if it is present in the lower right corner of the General tab in the properties dialog. This new release contains bug fixes and feature enhancements. There are some potential breaking changes in this release as some features of the Help File Builder have been moved into...C++ REST SDK (codename "Casablanca"): C++ REST SDK 1.3.0: This release fixes multiple customer reported issues as well as the following: Full support for Dev12 binaries and project files Full support for Windows XP New sample highlighting the Client and Server APIs : BlackJack Expose underlying native handle to set custom options on http_client Improvements to Listener Library Note: Dev10 binaries have been dropped as of this release, however the Dev10 project files are still available in the Source CodeNew Projects4Elements game project: Project for a game were players will be able to earn money by just playingBible: This project aims to deliver an awesome Bible application for as many platforms as possible.cIFrex: cIFrexConnecting SharePoint with Exchange Server 2010/2013 using remote sessions: The project focuses on connecting SharePoint 2013 with Exchange Server 2010/2013 via Remote PowerShell with C# API Crzy Cms: Crzy CMS is a content management system created in ASP.NET using MVC/Entity Framework.DownloadsArchiver: Kann automatisch das Downloads-Verzeichnis aufräumen.GatePass: Gatepass SystemGenerate PowerShell scripts for SharePoint 2010 Site Collection Administration: Winform tool to generate PowerShell scripts, to move, create, backup and restore site collections It needs to be run on SharePoint Server 2010Generate PowerShell scripts for SharePoint 2013 Site Collection Administration: Winform tool to generate PowerShell scripts, to move, create, backup and restore site collections It needs to be run on SharePoint Server 2013GTerm: GTerm is alternative Terminal for Windows Vista/XP/7 and 8.Ignitron Chess: A newly created software product for playing chess by Ignitron Development Team.Introduccion a C# con VS2012: El curso de Introducción a C# con Visual Studio 2012, tiene como objetivo principal enseñar al estudiante los conceptos básicos de programación utilizando C#Punch Clock: Punch Clock is a online tool for any employee to sign up and calculate their daily,weekly monthly hours and download the report in PDF/Excel format. PVMonitor: This project will provide a monitoring dashboard for PV systems.qttexteditor: qttexteditorRegister Interest app: Register Interest is an app template where you can use to record interest of attendees, useful in marketing distribution.SharePoint Simple Developer: Project allows to simply SharePoint 2010 and SharePoint 2013 daily developers tasks. Main goal is to implement validation of built solutions. Silverlight QB Rating Calculator: Silverlight QB Rating Calculator is a Silverlight 5 App that calculates a QB's NFL and NCAA passing efficiency ratings.SimpleAdditionPage: This projects consists of a simple ASP.NET in VB.NET page that allows users to enter 2 numbers, and display their sum.SP SIN Store: SP SIN Store is an extension to SP SIN that allows users to install solutions in SharePoint similar to the WordPress plugins. Project is in Alpha stage.

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• Help in decide the partition to install ubuntu

  - by G.Ashwin kumar

  I have a PC running with windows 7 ultimate 64 bit version with 4 gig Ram. I have a 320 gig hard disk , in which I have allocated 120 gig for windows 7, 100 gig for NY files(named ashwin in windows) and rest 80-90 gig partitioned but empty NTFS partition.Now where do I install Ubuntu so that windows and data is safe. I got the option install with windows I selected it , it then shows select drive(SCSI1 (0,0,0) (sda) -320.1 GB ATA WDC WD3200AAJS-6) and allocate driver by dragging the divider below which shows 66.5gb and 59.3 GB respectively. Which one do I go with? I clicked advance partitioning it shows five devices: device , type, m.point ,size.(mb), used(mb)......... /dev/sda1, NTFS, 104 , 35 (windows 7 loader) /dev/sda2, NTFS, 104752, 23604 /dev/sda3, NTFS, 125829, 10161 /dev/sda5, NTFS, 89382, 3221 when I checked size in properties it showed name of drive according to windows, used.Gb, free, total. ashwin, 10.2, 115.7, 125.8 c drive, 23.6, 81.1, 104.8 new volume, 92.6mb, 89.3, 89.4 except mentioned everything in gigabytes.ignore the last dots. I want to install it in new volume or using that space how do I do it? Explain in detail I'm a beginner.

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• Is a disk/ata timeout exception dangerous?

  - by j-g-faustus

  I have a few hard drives in mdadm RAID 5 configured to go to standby after a few minutes of inactivity. (Using hdparm.conf spindown_time.) At irregular intervals I get messages like these in dmesg: [ 1840.251661] ata4.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [ 1840.251722] ata4.00: failed command: SMART [ 1840.251758] ata4.00: cmd b0/d5:01:06:4f:c2/00:00:00:00:00/00 tag 0 pio 512 in [ 1840.251759] res 40/00:14:50:2e:04/00:00:02:00:00/40 Emask 0x4 (timeout) [ 1840.251858] ata4.00: status: { DRDY } [ 1840.251888] ata4: hard resetting link [ 1840.600742] ata4: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [ 1840.601521] ata4.00: configured for UDMA/133 [ 1840.601547] ata4: EH complete [337877.713988] ata4.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [337877.714019] ata4.00: failed command: SMART [337877.714038] ata4.00: cmd b0/d5:01:06:4f:c2/00:00:00:00:00/00 tag 0 pio 512 in [337877.714039] res 40/00:04:90:10:81/00:00:00:00:00/40 Emask 0x4 (timeout) [337877.714089] ata4.00: status: { DRDY } [337877.714107] ata4: hard resetting link [337878.063085] ata4: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [337878.063743] ata4.00: configured for UDMA/133 [337878.063764] ata4: EH complete I think the exception is caused by smartd when a drive does not wake up quickly enough. There are no issues (that I can tell) in accessing the drives normally through the file system - it takes a few seconds longer than normal when they are asleep, but there are no exceptions. Is this something I should worry about, as a potential symptom on something that could corrupt a drive over time? Or can I safely ignore it as part of normal operation? Edit: By request: smartctl -a for sdaand sde, both disks are members of the array. If ata4is the same as scsi-4 then sde is the one that gave the error above, according to /dev/disk/by-path.

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• How to fix "Disk drive for /boot/efi is not ready or not present"?

  - by N.N.

  After I updated BIOS/UEFI version to 1101 on an Asus P8Z68-V PRO motherboard Ubuntu (11.10) did not boot. After POST all I saw was a black screen with a blinking cursor in the top left corner. I booted an Ubuntu 11.10 live-CD and set the flag for the 20 MB partition before my boot partition to "bios_grub". Then I was able to boot and login. But now every time I boot and Ubuntu loads I get the following message: Disk drive for /boot/efi is not ready or not present. Continue waiting or press s to skip or m for manual recovery. I am able to login if I choose to ignore it by pressing s, but what does this message mean? How can I fix what the message warns about? After logging in I have noticed that /boot/efi is empty. The following forum post speaks of the same issue ubuntuforums.org/showthread.php?t=1893030. Updating to the latest BIOS/UEFI - version 3203, did not have any effect on this issue.

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• Setting up dual monitors, Xorg.conf issues

  - by JTS

  I just got a new computer (W520, Graphics card nVidia GF106 [Quadro 2000]) and installed ubuntu on it using wubi. I have everything working, so I wanted to set it up to be able to use two monitors with an extended screen. I figured I had to edit Xorg.conf, but the file didnt exist. So I tried to create it by booting in recovery mode, and executing Xorg -configure but I am getting these errors: (EE) Failed to load module "vmwgfx" (module does not exist, 0) (EE) vmware: Please ignore the above warnings about not being able to load module/driver vmwgfx (++) Using config file: "/root/xorg.conf.new" (==) Using system config directory "/usr/share/X11/xorg.conf.d" (EE) [drm] No DRICreatedPCIBusID symbol Number of created screens does not match number of detected devices. Configuration failed. ddxSigGiveUp: Closing log Any idea how I can get Xorg -configure to work, so that I can have an xorg.conf file that I can edit to enable twinview? EDIT: Another way I could ask the same question to solve this problem is, why can't I boot with an xorg.conf file generated by nvidia-xconfig? Is there something in the generated xorg.conf file that might need editing?

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• How to visualize the design of a program in order to communicate it to others

  - by Joris Meys

  I am (re-)designing some packages for R, and I am currently working out the necessary functions, objects, both internal and for the interface with the user. I have documented the individual functions and objects. So I have the description of all the little parts. Now I need to give an overview of how the parts fit together. The scheme of the motor so to say. I've started with making some flowchart-like graphs in Visio, but that quickly became a clumsy and useless collection of boxes, arrrows and-what-not. So hence the question: Is there specific software you can use for vizualizing the design of your program If so, care to share some tips on how to do this most efficiently If not, how do other designers create the scheme of their programs and communicate that to others? Edit: I am NOT asking how to explain complex processes to somebody, nor asking how to illustrate programming logic. I am asking how to communicate the design of a program/package, i.e.: the objects (with key features and representation if possible) the related functions (with arguments and function if possible) the interrelation between the functions at the interface and the internal functions (I'm talking about an extension package for a scripting language, keep that in mind) So something like this : But better. This is (part of) the interrelations between functions in the old package that I'm now redesigning for obvious reasons :-) PS : I made that graph myself, using code extraction tools on the source and feeding the interrelation matrix to yEd Graph Editor.

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• Inheritance vs composition in this example

  - by Gerenuk

  I'm wondering about the differences between inheritance and composition examined with concrete code relevant arguments. In particular my example was Inheritance: class Do: def do(self): self.doA() self.doB() def doA(self): pass def doB(self): pass class MyDo(Do): def doA(self): print("A") def doB(self): print("B") x=MyDo() vs Composition: class Do: def __init__(self, a, b): self.a=a self.b=b def do(self): self.a.do() self.b.do() x=Do(DoA(), DoB()) (Note for composition I'm missing code so it's not actually shorter) Can you name particular advantages of one or the other? I'm think of: composition is useful if you plan to reuse DoA() in another context inheritance seems easier; no additional references/variables/initialization method doA can access internal variable (be it a good or bad thing :) ) inheritance groups logic A and B together; even though you could equally introduce a grouped delegate object inheritance provides a preset class for the users; with composition you'd have to encapsule the initialization in a factory so that the user does have to assemble the logic and the skeleton ... Basically I'd like to examine the implications of inheritance vs composition. I heard often composition is prefered, but I'd like to understand that by example. Of course I can always start with one and refactor later to the other.

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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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• Named output parameters vs return values

  - by Abyx

  Which code is better: // C++ void handle_message(...some input parameters..., bool& wasHandled) void set_some_value(int newValue, int* oldValue = nullptr) // C# void handle_message(...some input parameters..., out bool wasHandled) void set_some_value(int newValue, out int oldValue) or bool handle_message(...some input parameters...) ///< Returns -1 if message was handled //(sorry, this documentation was broken a year ago and we're too busy to fix it) int set_some_value(T newValue) // (well, it's obvious what this function returns, so I didn't write any documentation for it) The first one doesn't have and need any documentation. It's a self-documenting code. Output value clearly says what it means, and it's really hard to make a change like this: - void handle_message(Message msg, bool& wasHandled) { - wasHandled = false; - if (...) { wasHandled = true; ... + void handle_message(Message msg, int& wasHandled) { + wasHandled = -1; + if (...) { wasHandled = ...; With return values such change could be done easily /// Return true if message was handled - bool handle_message(Message msg) { + int handle_message(Message msg) { ... - return true; + return -1; Most of compilers don't (and can't) check documentation written in comments. Programmers also tend to ignore comments while editing code. So, again, the question is: if subroutine has single output value, should it be a procedure with well-named self-documenting output parameter, or should it be a function which returns an unnamed value and have a comment describing it?

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• Impossible to boot Ubuntu on a USB stick (OS X Montain Lion)

  - by user109513

  I know this has been discussed over and over but I still cannot run Ubuntu on a USB stick. Here's the step I followed: 1. I downloaded Ubuntu 12.10 (ubuntu-12.10-desktop-i386.iso) from http://www.ubuntu.com/download/desktop which I renamed 'ubuntu.iso'. I bought my Mac mid-2010, it has an Intel processor. 2. I formated my 16GB USB stick with HFS+ File System following this tutorial: http://www.switchingtomac.com/tutorials/how-to-format-a-drive-or-partition-with-the-hfs-file-system 3. I opened a terminal and typed: hdiutil convert -format UDRW -o ~/Downloads/ubuntu.img ~/Downloads/ubuntu.iso It created ubuntu.iso.dmg 4. I ran 'diskutil list' and identified the device node assigned to the USB. 5. I unmounted it: diskutil unmountDisk /dev/disk2 6. Then, I entered the command: sudo dd if=~/Downloads/ubuntu.img.dmg of=/dev/rdisk2 bs=1m. It seemed to work. A Mac message poped up saying that the system doesn't recognized the disk, I pressed 'ignore'. 7. I ejected the USB using diskutil eject /dev/disk2, then removed the USB. 8. I rebooted the computer, plugged the USB key, pressed ALT.I could see my Macintosh partition and my Windows partition, but couldn't see my USB stick. Any help will be very appreciated :) Victor

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• I don't understand the definition of side effects

  - by Chris Okyen

  I don't understand the wikipedia article on Side Effects: In computer science, a function or expression is said to have a side effect if, in addition to returning a value, it also 1.) Modifies some state or 2.) Has an observable interaction with calling functions or the outside world. I know an example of the first thing that causes a function or expression to have side effects - modifying a state Function and Expression modifying a state : 1.) foo(int X) { return x = x % x; } a = a + 1; What does 2.) - Has an observable interaction with calling functions or the outside world," mean? - Please give an example. The article continues on to say, "For example, a function might modify a global or static variable, modify one of its arguments, raise an exception, write data to a display or file, read data, or call other side-effecting functions...." Are all these examples, examples of 1.) - Modifiying some state , or are they also part of 2.) - Has an observable interaction with calling functions or the outside world?

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• Happy Tau Day! (Or: How Some Mathematicians Think We Should Retire Pi) [Video]

  - by Jason Fitzpatrick

  When you were in school you learned all about Pi and its relationship to circles and turn-based geometry. Some mathematicians are rallying for a new lesson, on about Tau. Michael Hartl is a mathematician on a mission, a mission to get people away from using Pi and to start using Tau. His manifesto opens: Welcome to The Tau Manifesto. This manifesto is dedicated to one of the most important numbers in mathematics, perhaps the most important: the circle constant relating the circumference of a circle to its linear dimension. For millennia, the circle has been considered the most perfect of shapes, and the circle constant captures the geometry of the circle in a single number. Of course, the traditional choice of circle constant is p—but, as mathematician Bob Palais notes in his delightful article “p Is Wrong!”,1 p is wrong. It’s time to set things right. Why is Pi wrong? Among the arguments is that Tau is the ration of a circumference to the radius of a circle and defining circles by their radius is more natural and that Pi is a 2-factor number but with Tau everything is based of a single unit–three quarters of a turn around a Tau-defined circle is simply three quarters of a Tau radian. Watch the video above to see the Tau sequence (which begins 6.2831853071…) turned into a musical composition. For more information about Tau hit up the link below to read the manifesto. The Tau Manifesto [TauDay] HTG Explains: Photography with Film-Based CamerasHow to Clean Your Dirty Smartphone (Without Breaking Something)What is a Histogram, and How Can I Use it to Improve My Photos?

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• How to create a copy of an instance without having access to private variables

  - by Jamie

  Im having a bit of a problem. Let me show you the code first: public class Direction { private CircularList xSpeed, zSpeed; private int[] dirSquare = {-1, 0, 1, 0}; public Direction(int xSpeed, int zSpeed){ this.xSpeed = new CircularList(dirSquare, xSpeed); this.zSpeed = new CircularList(dirSquare, zSpeed); } public Direction(Point dirs){ this(dirs.x, dirs.y); } public void shiftLeft(){ xSpeed.shiftLeft(); zSpeed.shiftRight(); } public void shiftRight(){ xSpeed.shiftRight(); zSpeed.shiftLeft(); } public int getXSpeed(){ return this.xSpeed.currentValue(); } public int getZSpeed(){ return this.zSpeed.currentValue(); } } Now lets say i have an instance of Direction: Direction dir = new Direction(0, 0); As you can see in the code of Direction, the arguments fed to the constructor, are passed directly to some other class. One cannot be sure if they stay the same because methods shiftRight() and shiftLeft could have been called, which changes thos numbers. My question is, how do i create a completely new instance of Direction, that is basically copy(not by reference) of dir? The only way i see it, is to create public methods in both CircularList(i can post the code of this class, but its not relevant) and Direction that return the variables needed to create a copy of the instance, but this solution seems really dirty since those numbers are not supposed to be touched after beeing fed to the constructor, and therefore they are private.

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• Serious error on first attempts to dual boot Ubuntu 14.04 with Win7

  - by beetle

  I downloaded Ubuntu 14.04 from the website which I saved to my desktop with WinRar. My trial with winrar had expired so I have now tried it with Active@Isoburner but I'm getting no further. I eventually got it burnt onto a DVD(4.7gb) and tried to boot from DVD and normally. Neither way works. It looks like its about to boot but then a message appears saying that a serious error has occurred...the disk drive for /tmp is not ready yet or not present...press I to ignore, s to skip or m for manual... At this point I'm lost and unsure what to do. My laptop Toshiba Equium A210-17I is over 5 or 6 years old. Available space on the Hard Drive is 24gb. 2gb RAM. It originally came with Windows Vista Home Premium edition but about a year ago or more a friend wiped it clean for me as I was having no end of problems with Vista. He installed Windows 7 Ultimate(which I don't have a disc for). How can I resolve this issue and get Ubuntu to boot up? Do I have to install a previous version of Ubuntu first? Any advice or help would be greatly appreciated. Kind regards. Beetle.

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• Empty interface to combine multiple interfaces

  - by user1109519

  Suppose you have two interfaces: interface Readable { public void read(); } interface Writable { public void write(); } In some cases the implementing objects can only support one of these but in a lot of cases the implementations will support both interfaces. The people who use the interfaces will have to do something like: // can't write to it without explicit casting Readable myObject = new MyObject(); // can't read from it without explicit casting Writable myObject = new MyObject(); // tight coupling to actual implementation MyObject myObject = new MyObject(); None of these options is terribly convenient, even more so when considering that you want this as a method parameter. One solution would be to declare a wrapping interface: interface TheWholeShabam extends Readable, Writable {} But this has one specific problem: all implementations that support both Readable and Writable have to implement TheWholeShabam if they want to be compatible with people using the interface. Even though it offers nothing apart from the guaranteed presence of both interfaces. Is there a clean solution to this problem or should I go for the wrapper interface? UPDATE It is in fact often necessary to have an object that is both readable and writable so simply seperating the concerns in the arguments is not always a clean solution. UPDATE2 (extracted as answer so it's easier to comment on) UPDATE3 Please beware that the primary usecase for this is not streams (although they too must be supported). Streams make a very specific distinction between input and output and there is a clear separation of responsibilities. Rather, think of something like a bytebuffer where you need one object you can write to and read from, one object that has a very specific state attached to it. These objects exist because they are very useful for some things like asynchronous I/O, encodings,...

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• Why is Desktop Unity using the global application menu?

  - by Kazade

  It was announced in another question that the desktop version of Unity will keep the global menu by default. Here are the facts: The global menu was introduced into UNE to save vertical screen space because at Netbook resolutions the vertical space is limited. On a modern desktop with a high resolution, there is ample vertical space making this unnecessary On the announcement of UNE global menus, Mark Shuttleworth himself said the following: "There are outstanding questions about the usability of a panel-hosted menu on much larger screens, where the window and the menu could be very far apart." The benefits of a global menu don't seem to carry across to a high-resolution desktop and instead seem to bring draw backs (increased mouse travel, large distance between the menu and its associated window). The other worrying factor is that applications seem to be moving away from having a menu bar, and instead of innovating on this and defining new guidelines for moving away from the menu, we are giving it prime place right at the top of the desktop. If applications continue moving away from the desktop we will have an inconsistent experience concerning where to locate application related options/tools depending on which app you are using (e.g. Chrome). Finally, the current global menu bar implementation doesn't work for all apps, and doesn't even work for all apps in the default install. This means that the default desktop implementation will be inconsistent. So, there are a bunch of reasons why moving to a global menu is a bad idea, so we need some pretty convincing arguments for why it is a good idea. What are the reasons for the global menu implementation in the desktop version of Unity?

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• When mapping the surface of a sphere with tiles, how might you deal with polar distortion?

  - by clweeks

  It's easy to deal with the way locations interact on a clean Cartesian grid. It's just vanilla math. And you can kind of ignore the geometry of the sphere's surface for a bunch of it if you want to just truncate the poles or something. But I keep coming up with ideas for games where the polar space matters. Geo-coded ARGs and global roguelikes and stuff. I want square(ish?) locations -- reasonably representable by square tiles of the same size across the globe, anyway. This has to be a solved problem, right? What are the solutions? ETA: At the equator -- and assuming that your square locations are reasonably small, it's close enough to true that you can get away with having one square in the rows north and south of the most equatorial row. And you could probably get away with that by just hand-waving the difference up to like 45-degrees or so. But eventually, you need to have fewer squares in a pole-ward circumferential row. If I reduce the length of the row by one and offset the squares by 1/2 then they're just like hexes and it's relatively easy to do the coding to keep track of the connections. But as you get pole-ward, it gets more and more extreme. Projecting the surface of the world onto the surface of a cube is tempting. But I figured there must be more elegant solutions already in use. If I did the cube thing (not dissecting it further through geodesy) Are there any pros and cons related to placing the pole at the center of a face or at the vertex of three sides?

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• Problem inserting pre-ordered values to quadtree

  - by Lucas Corrêa Feijó

  There's this string containing B, W and G (standing for black, white and gray). It defines the pre-ordered path of the quadtree I want to build. I wrote this method for filling the QuadTree class I also wrote but it doesn't work, it inserts correctly until it reaches a point in the algorithm it needs to "return". I use math quadrants convention order for insertion, such as northeast, northwest, southwest and southeast. A quadtree has all it's leafs black or white and all the other nodes gray The node used in the tree is called Node4T and has a char as data and 4 references to other nodes like itself, called, respectively NE, NW, SW, SE. public void insert(char val) { if(root==null) { root = new Node4T(val); } else { insert(root, val); } } public void insert(Node4T n, char c) { if(n.data=='G') // possible to insert { if(n.NE==null) { n.NE = new Node4T(c); return; } else { insert(n.NE,c); } if(n.NW==null) { n.NW = new Node4T(c); return; } else { insert(n.NW,c); } if(n.SW==null) { n.SW = new Node4T(c); return; } else { insert(n.SW,c); } if(n.SE==null) { n.SE = new Node4T(c); return; } else { insert(n.SE,c); } } else // impossible to insert { } } The input "GWGGWBWBGBWBWGWBWBWGGWBWBWGWBWBGBWBWGWWWB" is given a char at a time to the insert method and then the print method is called, pre-ordered, and the result is "GWGGWBWBWBWGWBWBW". How do I make it import the string correctly? Ignore the string reading process, suppose the method is called and it has to do it's job.

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