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  • How do I create a 12.04 LiveUSB for a non-PAE machine?

    - by DrSkylaser
    I'm trying to create a dual-boot laptop with Ubuntu 12.04 and some flavor of Windows (TBD). To do that, I need to do some work on partitions & install 12.04. To do that, I need to create a bootable USB that will work with my non-PAE-capable CPU. Someone pointed me to a mini.iso that was allegedly non-PAE-friendly, but it gave me the same error as the straightup 12.04 desktop ISO. What version do I actually need? (This isn't going to be a virtual machine--I don't think the laptop has the RAM to handle that happily--so enabling PAE in the virtual machineware doesn't help me.)

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  • Teaching: How can you motivate students to comment?

    - by keflavich
    I remember when I was taught, "comments are the most important part of code." Or rather, when I was told that comments are the most important part of the code. I don't think I was convinced, and I still see common cases where programmers are not convinced of the necessity of good & thorough comments. I am certainly convinced myself at this point - trying to read, in particular, complex formulae that call functions that call other functions that I don't understand - but I don't know how to convey this to students.

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  • Should I extract specific functionality into a function and why?

    - by john smith optional
    I have a large method which does 3 tasks, each of them can be extracted into a separate function. If I'll make an additional functions for each of that tasks, will it make my code better or worse and why? Edit: Obviously, it'll make less lines of code in the main function, but there'll be additional function declarations, so my class will have additional methods, which I believe isn't good, because it'll make the class more complex. Edit2: Should I do that before I wrote all the code or should I leave it until everything is done and then extract functions?

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  • ALL, ALLEXCEPT and VALUES in DAX

    - by Marco Russo (SQLBI)
    When you use CALCULATE in DAX you are creating a new filter context for the calculation, based on the existing one. There are a few functions that are used to clear or preserve a column filter. These functions are: ALL – it can be used with one or more columns from a table, or with the name of a table. It returns all the values from the column(s) or all the rows from the table, ignoring any existing filter context. In other words, ALL clear an existing filter context on columns or table. We can use...(read more)

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  • How to control fan speed and temperatures on Asus A8Js laptop?

    - by Azeworai
    I have tried installing asusfan and lm-sensors but I'm unable to control my fans to cool my laptop down sufficiently. Currently it overheats at about 100 degrees celsius and my sensors output somehow does not have any fan information on it: jackson@OLYMPIA:~$ sensors acpitz-virtual-0 Adapter: Virtual device temp1: +69.0°C (crit = +110.0°C) coretemp-isa-0000 Adapter: ISA adapter Core 0: +66.0°C (high = +100.0°C, crit = +100.0°C) coretemp-isa-0001 Adapter: ISA adapter Core 1: +66.0°C (high = +100.0°C, crit = +100.0°C) I have checked my bios and there isn't any fan settings there. I can consistently overheat just by converting a video via Handbrake. I have ubuntu-desktop installed for a GUI. Is there a way for me to control my fans to start spinning before it reaches a critical temperature and kills itself?

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  • Does the Ubuntu mini.iso work with EFI?

    - by jean388
    I have to install Ubuntu 11.10 from the AMD64 mini.iso on a system with UEFI BIOS motherboard. I have configured a virtual machine in VirtualBox for making a test install before I setup the real system. In VirtualBox I have enabled EFI. When the virtual machine is powered on and boot mini.iso the Grub commandline is shown. If I try to boot the normal Ubuntu CD it works fine and I get the normal boot options "Install Ubuntu" etc. Does Ubuntu mini.iso not work with EFI?

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  • Problem with WindowsXp on VirtualBox in 12.10

    - by umpirsky
    When I try to start it I get: Failed to open a session for the virtual machine WindowsXp. The virtual machine 'WindowsXp' has terminated unexpectedly during startup with exit code 1. Result Code: NS_ERROR_FAILURE (0x80004005) Component: Machine Interface: IMachine {5eaa9319-62fc-4b0a-843c-0cb1940f8a91} and in another dialog: Kernel driver not installed (rc=-1908) The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a permission problem with /dev/vboxdrv. Please reinstall the kernel module by executing '/etc/init.d/vboxdrv setup' as root. If it is available in your distribution, you should install the DKMS package first. This package keeps track of Linux kernel changes and recompiles the vboxdrv kernel module if necessary. When I try to run: $ sudo /etc/init.d/vboxdrv setup [sudo] password for umpirsky: sudo: /etc/init.d/vboxdrv: command not found Any idea?

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  • What is upcasting/downcasting?

    - by acidzombie24
    When learning about polymorphism you commonly see something like this class Base { int prv_member; virtual void fn(){} } class Derived : Base { int more_data; virtual void fn(){} } What is upcasting or downcasting? Is (Derived*)base_ptr; an upcast or downcast? I call it upcast because you are going away from the base into something more specific. Other people told me it is a downcast because you are going down a hierarchy into something specific with the top being the root. But other people seem to call it what i call it. When converting a base ptr to a derived ptr is it called upcasting or downcasting? and if someone can link to an official source or explain why its called that than great.

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  • Is there a name for this functional programming construct/pattern?

    - by dietbuddha
    I wrote a function and I'd like to find out if it is an implementation of some functional programming pattern or construct. I'd like to find out the name of this pattern or construct (if it exists)? I have a function which takes a list of functions and does this to them: wrap(fn1, fn2, fn3, fn4) # returns partial(fn4, partial(fn3, partial(fn2, fn1))) There are strong similarities to compose, reduce, and other fp metaprogramming constructs, since the functions are being arranged together and returned as one function. It also has strong similarities to decorators and Python context managers since it provides a way to encapsulate pre and post execution behaviors in one function. Which was the impetus for writing this function. I wanted the ability that context managers provide, but I wanted to be able to have it defined in one function, and to be able to layer function after function on top.

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  • Bullet Physics implementing custom MotionState class

    - by Arosboro
    I'm trying to make my engine's camera a kinematic rigid body that can collide into other rigid bodies. I've overridden the btMotionState class and implemented setKinematicPos which updates the motion state's tranform. I use the overridden class when creating my kinematic body, but the collision detection fails. I'm doing this for fun trying to add collision detection and physics to Sean O' Neil's Procedural Universe I referred to the bullet wiki on MotionStates for my CPhysicsMotionState class. If it helps I can add the code for the Planetary rigid bodies, but I didn't want to clutter the post. Here is my motion state class: class CPhysicsMotionState: public btMotionState { protected: // This is the transform with position and rotation of the camera CSRTTransform* m_srtTransform; btTransform m_btPos1; public: CPhysicsMotionState(const btTransform &initialpos, CSRTTransform* srtTransform) { m_srtTransform = srtTransform; m_btPos1 = initialpos; } virtual ~CPhysicsMotionState() { // TODO Auto-generated destructor stub } virtual void getWorldTransform(btTransform &worldTrans) const { worldTrans = m_btPos1; } void setKinematicPos(btQuaternion &rot, btVector3 &pos) { m_btPos1.setRotation(rot); m_btPos1.setOrigin(pos); } virtual void setWorldTransform(const btTransform &worldTrans) { btQuaternion rot = worldTrans.getRotation(); btVector3 pos = worldTrans.getOrigin(); m_srtTransform->m_qRotate = CQuaternion(rot.x(), rot.y(), rot.z(), rot.w()); m_srtTransform->SetPosition(CVector(pos.x(), pos.y(), pos.z())); m_btPos1 = worldTrans; } }; I add a rigid body for the camera: // Create rigid body for camera btCollisionShape* cameraShape = new btSphereShape(btScalar(5.0f)); btTransform startTransform; startTransform.setIdentity(); // forgot to add this line CVector vCamera = m_srtCamera.GetPosition(); startTransform.setOrigin(btVector3(vCamera.x, vCamera.y, vCamera.z)); m_msCamera = new CPhysicsMotionState(startTransform, &m_srtCamera); btScalar tMass(80.7f); bool isDynamic = (tMass != 0.f); btVector3 localInertia(0,0,0); if (isDynamic) cameraShape->calculateLocalInertia(tMass,localInertia); btRigidBody::btRigidBodyConstructionInfo rbInfo(tMass, m_msCamera, cameraShape, localInertia); m_rigidBody = new btRigidBody(rbInfo); m_rigidBody->setCollisionFlags(m_rigidBody->getCollisionFlags() | btCollisionObject::CF_KINEMATIC_OBJECT); m_rigidBody->setActivationState(DISABLE_DEACTIVATION); This is the code in Update() that runs each frame: CSRTTransform srtCamera = CCameraTask::GetPtr()->GetCamera(); Quaternion qRotate = srtCamera.m_qRotate; btQuaternion rot = btQuaternion(qRotate.x, qRotate.y, qRotate.z, qRotate.w); CVector vCamera = CCameraTask::GetPtr()->GetPosition(); btVector3 pos = btVector3(vCamera.x, vCamera.y, vCamera.z); CPhysicsMotionState* cameraMotionState = CCameraTask::GetPtr()->GetMotionState(); cameraMotionState->setKinematicPos(rot, pos);

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  • VMMap - awesome memory analysis tool

    VMMap is a process virtual and physical memory analysis utility. It shows a breakdown of a process's committed virtual memory types as well as the amount of physical memory (working set) assigned by the operating system to those types. Besides graphical representations of memory usage, VMMap also shows summary information and a detailed process memory map. Powerful filtering and refresh capabilities allow you to identify the sources of process memory usage and the memory cost of application features. Besides flexible views for analyzing live processes, VMMap supports the export of data in multiple forms, including a native format that preserves all the information so that you can load back in. It also includes command-line options that enable scripting scenarios. VMMap is the ideal tool for developers wanting to understand and optimize their application's memory resource usage. span.fullpost {display:none;}

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  • Problem Trying to Install ROOT (by CERN) on Ubuntu 11.04 i386

    - by Jose Luis
    I hope you can help me with this problem I am trying to install root in my computer, but I have a problem and I don't know what to do to solve it I've downloaded the tar file with the root version that I want to install I've extracted the files in the tar file I've run the configure program succesfully, but when I run "make" command I get this result: cp /root/root/core/utils/src/RClStl.cxx core/utils/src/RClStl_tmp.cxx bin/rmkdepend -R -fcore/utils/src/RClStl_tmp.d -Y -w 1000 -- -pipe -m32 -Wall -W -Woverloaded-virtual -fPIC -Iinclude -DR__HAVE_CONFIG -pthread -UR__HAVE_CONFIG -DROOTBUILD -I/root/root/core/utils/src -D__cplusplus -- core/utils/src/RClStl_tmp.cxx g++ -O2 -pipe -m32 -Wall -W -Woverloaded-virtual -fPIC -Iinclude -DR__HAVE_CONFIG -pthread -UR__HAVE_CONFIG -DROOTBUILD -I/root/root/core/utils/src -o core/utils/src/RClStl_tmp.o -c core/utils/src/RClStl_tmp.cxx In file included from core/utils/src/RClStl.h:28:0, from core/utils/src/RClStl_tmp.cxx:16: core/utils/src/Scanner.h:16:27: fatal error: clang/AST/AST.h: No existe el fichero o el directorio compilation terminated. make: * [core/utils/src/RClStl_tmp.o] Error 1 rm core/utils/src/RClStl_tmp.cxx I don´t know what to do Please, help me thank you in advance

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  • VMMap - awesome memory analysis tool

    VMMap is a process virtual and physical memory analysis utility. It shows a breakdown of a process's committed virtual memory types as well as the amount of physical memory (working set) assigned by the operating system to those types. Besides graphical representations of memory usage, VMMap also shows summary information and a detailed process memory map. Powerful filtering and refresh capabilities allow you to identify the sources of process memory usage and the memory cost of application features. Besides flexible views for analyzing live processes, VMMap supports the export of data in multiple forms, including a native format that preserves all the information so that you can load back in. It also includes command-line options that enable scripting scenarios. VMMap is the ideal tool for developers wanting to understand and optimize their application's memory resource usage. span.fullpost {display:none;}

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  • How to export a C++ class library to C# using a dll?

    - by SICGames2013
    In my previous revision game engine I deported major functions for the game editor for C#. Now, I'm beginning to revise the game engine with a static library. There's a already dynamic library created in C++ to use DLLEXPORT for C#. Just now I want to test out the newer functions and created a DLL file from C++. Because the DLL contains classes I was wondering how would I be able to use DLL Export. Would I do this: [DLLEXPORT("GameEngine.dll", EntryPoint="SomeClass", Conventional=_stdcall)] static extern void functionFromClass(); I have a feeling it's probably DLLImport and not DLLExport. I was wondering how would I go about this? Another way I was thinking was because I already have the DLL in C++ prepared already to go the C# Class Library. I could just keep the new engine as a lib, and link the lib with the old DLL C++ file. Wouldn't the EntryPoint be able to point to the class the function is in?

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  • Migrating R Scripts from Development to Production

    - by Mark Hornick
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 “How do I move my R scripts stored in one database instance to another? I have my development/test system and want to migrate to production.” Users of Oracle R Enterprise Embedded R Execution will often store their R scripts in the R Script Repository in Oracle Database, especially when using the ORE SQL API. From previous blog posts, you may recall that Embedded R Execution enables running R scripts managed by Oracle Database using both R and SQL interfaces. In ORE 1.3.1., the SQL API requires scripts to be stored in the database and referenced by name in SQL queries. The SQL API enables seamless integration with database-based applications and ease of production deployment. Loading R scripts in the repository Before talking about migration, we’ll first introduce how users store R scripts in Oracle Database. Users can add R scripts to the repository in R using the function ore.scriptCreate, or SQL using the function sys.rqScriptCreate. For the sample R script     id <- 1:10     plot(1:100,rnorm(100),pch=21,bg="red",cex =2)     data.frame(id=id, val=id / 100) users wrap this in a function and store it in the R Script Repository with a name. In R, this looks like ore.scriptCreate("RandomRedDots", function () { line-height: 115%; font-family: "Courier New";">     id <- 1:10     plot(1:100,rnorm(100),pch=21,bg="red",cex =2)     data.frame(id=id, val=id / 100)) }) In SQL, this looks like begin sys.rqScriptCreate('RandomRedDots',  'function(){     id <- 1:10     plot(1:100,rnorm(100),pch=21,bg="red",cex =2)     data.frame(id=id, val=id / 100)   }'); end; / The R function ore.scriptDrop and SQL function sys.rqScriptDrop can be used to drop these scripts as well. Note that the system will give an error if the script name already exists. Accessing R scripts once they’ve been loaded If you’re not using a source code control system, it is possible that your R scripts can be misplaced or files modified, making what is stored in Oracle Database to only or best copy of your R code. If you’ve loaded your R scripts to the database, it is straightforward to access these scripts from the database table SYS.RQ_SCRIPTS. For example, select * from sys.rq_scripts where name='myScriptName'; From R, scripts in the repository can be loaded into the R client engine using a function similar to the following: ore.scriptLoad <- function(name) { query <- paste("select script from sys.rq_scripts where name='",name,"'",sep="") str.f <- OREbase:::.ore.dbGetQuery(query) assign(name,eval(parse(text = str.f)),pos=1) } ore.scriptLoad("myFunctionName") This function is also useful if you want to load an existing R script from the repository into another R script in the repository – think modular coding style. Just include this function in the body of the other function and load the named script. Migrating R scripts from one database instance to another To move a set of functions from one system to another, the following script loads the functions from one R script repository into the client R engine, then connects to the target database and creates the scripts there with the same names. scriptNames <- OREbase:::.ore.dbGetQuery("select name from sys.rq_scripts where name not like 'RQG$%' and name not like 'RQ$%'")$NAME for(s in scriptNames) { cat(s,"\n") ore.scriptLoad(s) } ore.disconnect() ore.connect("rquser","orcl","localhost","rquser") for(s in scriptNames) { cat(s,"\n") ore.scriptDrop(s) ore.scriptCreate(s,get(s)) } Best Practice When naming R scripts, keep in mind that the name can be up to 128 characters. As such, consider organizing scripts in a directory structure manner. For example, if an organization has multiple groups or applications sharing the same database and there are multiple components, use “/” to facilitate the function organization: line-height: 115%;">ore.scriptCreate("/org1/app1/component1/myFuntion1", myFunction1) ore.scriptCreate("/org1/app1/component1/myFuntion2", myFunction2) ore.scriptCreate("/org1/app2/component2/myFuntion2", myFunction2) ore.scriptCreate("/org2/app2/component1/myFuntion3", myFunction3) ore.scriptCreate("/org3/app2/component1/myFuntion4", myFunction4) Users can then query for all functions using the path prefix when looking up functions. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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  • Is possible to write too many asserts?

    - by Lex Fridman
    I am a big fan of writing assert checks in C++ code as a way to catch cases during development that cannot possibly happen but do happen because of logic bugs in my program. This is a good practice in general. However, I've noticed that some functions I write (which are part of a complex class) have 5+ asserts which feels like it could potentially be a bad programming practice, in terms of readability and maintainability. I think it's still great, as each one requires me to think about pre- and post-conditions of functions and they really do help catch bugs. However, I just wanted to put this out there to ask if there is a better paradigms for catching logic errors in cases when a large number of checks is necessary.

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  • Are closures with side-effects considered "functional style"?

    - by Giorgio
    Many modern programming languages support some concept of closure, i.e. of a piece of code (a block or a function) that Can be treated as a value, and therefore stored in a variable, passed around to different parts of the code, be defined in one part of a program and invoked in a totally different part of the same program. Can capture variables from the context in which it is defined, and access them when it is later invoked (possibly in a totally different context). Here is an example of a closure written in Scala: def filterList(xs: List[Int], lowerBound: Int): List[Int] = xs.filter(x => x >= lowerBound) The function literal x => x >= lowerBound contains the free variable lowerBound, which is closed (bound) by the argument of the function filterList that has the same name. The closure is passed to the library method filter, which can invoke it repeatedly as a normal function. I have been reading a lot of questions and answers on this site and, as far as I understand, the term closure is often automatically associated with functional programming and functional programming style. The definition of function programming on wikipedia reads: In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state. and further on [...] in functional code, the output value of a function depends only on the arguments that are input to the function [...]. Eliminating side effects can make it much easier to understand and predict the behavior of a program, which is one of the key motivations for the development of functional programming. On the other hand, many closure constructs provided by programming languages allow a closure to capture non-local variables and change them when the closure is invoked, thus producing a side effect on the environment in which they were defined. In this case, closures implement the first idea of functional programming (functions are first-class entities that can be moved around like other values) but neglect the second idea (avoiding side-effects). Is this use of closures with side effects considered functional style or are closures considered a more general construct that can be used both for a functional and a non-functional programming style? Is there any literature on this topic? IMPORTANT NOTE I am not questioning the usefulness of side-effects or of having closures with side effects. Also, I am not interested in a discussion about the advantages / disadvantages of closures with or without side effects. I am only interested to know if using such closures is still considered functional style by the proponent of functional programming or if, on the contrary, their use is discouraged when using a functional style.

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  • Public versus private inheritance when some of the parent's methods need to be exposed?

    - by Vorac
    Public inheritance means that all fields from the base class retain their declared visibility, while private means that they are forced to 'private' within the derived class's scope. What should be done if some of the parent's members (say, methods) need to be publicly exposed? I can think of two solution. Public inheritance somewhat breaks encapsulation. Furthermore, when you need to find out where is the method foo() defined, one needs to look at a chain of base classes. Private inheritance solves these problems, but introduces burden to write wrappers (more text). Which might be a good thing in the line of verbosity, but makes changes of interfaces incredibly cumbersome. What considerations am I missing? What constraints on the type of project are important? How to choose between the two (I am not even mentioning 'protected')? Note that I am targeting non-virtual methods. There isn't such a discussion for virtual methods (or is there).

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  • Java best practice Interface - subclasses and constants

    - by Taiko
    In the case where a couple of classes implements an interface, and those classes have a couple of constants in common (but no functions), were should I put this constant ? I've had this problem a couple of times. I have this interface : DataFromSensors that I use to hide the implementations of several sub classes like DataFromHeartRateMonitor DataFromGps etc... For some reason, those classes uses the same constants. And there's nowere else in the code were it is used. My question is, were should I put those constants ? Not in the interface, because it has nothing to do with my API Not in a static Constants class, because I'm trying to avoid those Not in a common abstract class, that would stand between the interface and the subclasses, because I have no functions in common, only a couple of constants (TIMEOUT_DURATION, UUID, those kind of things) I've read best practice for constants and interface to define constants but they don't really answer my question. Thanks !

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  • How to write comments to explain the "why" behind the callback function when the function and parameter names are insufficient for that?

    - by snowmantw
    How should I approach writing comments for callback functions? I want to explain the "why" behind the function when the function and parameter names are insufficient to explain what's going on. I have always wonder why comments like this can be so ordinary in documents of libraries in dynamic languages: /** * cb: callback // where's the arguments & effects? */ func foo( cb ) Maybe the common attitude is "you can look into source code on your own after all" which pushes people into leaving minimalist comments like this. But it seems like there should be a better way to comment callback functions. I've tried to comment callbacks in Haskell way: /** * cb: Int -> Char */ func foo(cb) And to be fair, it's usually neat enough. But it gets into trouble when I need to pass some complex structure. The problem being partly due to the lack of type system: /** * cb: Int -> { err: String -> (), success: () -> Char } // too long... */ func foo(cb) Or I have tried this too: /** * cb: Int -> { err: String -> (), * success: () -> Char } // better ? */ func bar(cb) The problem is that you may put the structure in somewhere else, but you must give it a name to reference it. But then when you name a structure you're about to use immediately looks so redundant: // Somewhere else... // ResultCallback: { err: String -> (), success: () -> Char } /** * cb: Int -> ResultCallback // better ?? */ func foo(cb) And it bothers me if I follow the Java-doc like commenting style since it still seems incomplete. The comments don't tell you anything that you couldn't immediately see from looking at the function. /** * @param cb {Function} yeah, it's a function, but you told me nothing about it... * @param err {Function} where should I put this callback's argument ?? * Not to mention the err's own arguments... */ func foo(cb) These examples are JavaScript like with generic functions and parameter names, but I've encountered similar problems in other dynamic languages which allow complex callbacks.

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  • I loose some directories when i upgrade from Ubuntu 11.10 to 12.04

    - by maythux
    last day i upgraded my ubunut 11.10 desktop to ubuntu 12.04. I was running a KVM virtual about 7 machines and managed by virt-manage software.... anyway when i finished upgrading i found that virt-manager is not working so i have to reconfigure it again and install some other missing packages that was deleted!!!! anyway i solve this issue...then i started to restore my virtual machines i restore 2 machines without any problems the third and fourth ones (windows) make a check disk that takes more that 6 hours but finally it works... other machines i cant find their attached hard disks i don't know what happens but i cant found that files. 1- upgrading delete files!?!! 2- Is there anyway to restore those files? thanks in advance

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  • package update in ubuntu on vitual box

    - by Ayusman
    while following one of the tutorials I needed to install a curl package. Here are my system configuration: Virtualbox 4.1 on Windows 7 64 bit. I have installed ubuntu 12.04 on the virtual box. When I try the following: sudo apt-get install curl I see the following errors: [sudo] password for userMe: Reading package lists... Done Building dependency tree Reading state information... Done Package curl is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package 'curl' has no installation candidate userMe@userMe-ubuntu:~$ When I try the same on a direct installation of ubuntu on a laptop (not a virtual machine) there is no problem. I am assuming this may be because of network settings. Please note that my work PC is in a corporate network and uses auto proxy settings (using a .pac file) for internet access etc. Any help will be appreciated.

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  • Using static in PHP

    - by nischayn22
    I have a few functions in PHP that read data from functions in a class readUsername(int userId){ $reader = getReader(); return $reader->getname(userId); } readUserAddress(){ $reader = getReader(); return $reader->getaddress(userId); } All these make a call to getReader() { require_once("Reader.php"); static $reader = new Reader(); return $reader; } An overview of Reader class Reader{ getname(int id) { //if in-memory cache exists for this id return that //else get from db and cache it } getaddress(int id) { $this->getname(int id); //get address from name here } /*Other stuff*/ } Why is class Reader needed The Reader class does some in-memory caching of user details. So, I need only one object of class Reader and it will cache the user details instead of making multiple db calls. I am using static so that it the object gets created only once. Is this the right approach or should I do something else?

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  • Passing class names or objects?

    - by nischayn22
    I have a switch statement switch ( $id ) { case 'abc': return 'Animal'; case 'xyz': return 'Human'; //many more } I am returning class names,and use them to call some of their static functions using call_user_func(). Instead I can also create a object of that class, return that and then call the static function from that object as $object::method($param) switch ( $id ) { case 'abc': return new Animal; case 'xyz': return new Human; //many more } Which way is efficient? To make this question broader : I have classes that have mostly all static methods right now, putting them into classes is kind of a grouping idea here (for example the DB table structure of Animal is given by class Animal and so for Human class). I need to access many functions from these classes so the switch needs to give me access to the class

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  • Ubuntu boots into terminal

    - by DKuntz2
    When I turn on my computer (a CR-48), I keep loading tty1. I have tried xstart, and all I get is: Fatal server error: Could not create lock file in /tmp/.tX0-lock When I attempted to make the directory (both sudo and not), I received these two errors: sudo: Can't open /var/lib/sudo/don/tty2: Read-only file system (I've gotten other tty's for different virtual terminals) mkdir: cannot create directory '/tmp/tX0-lock': Read-only file system Before I got to the only terminal state, I had the computer moving a few files from a network server to the computer, I put it to sleep without stopping the transfers, and started the computer again away from my home network, and attempted to stop the transfers, the computer than restarted. Running sudo reboot puts me right back in the virtual terminal, and I can't get into any sort of x application.

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