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  • What Precalculus knowledge is required before learning Discrete Math Computer Science topics?

    - by Ein Doofus
    Below I've listed the chapters from a Precalculus book as well as the author recommended Computer Science chapters from a Discrete Mathematics book. Although these chapters are from two specific books on these subjects I believe the topics are generally the same between any Precalc or Discrete Math book. What Precalculus topics should one know before starting these Discrete Math Computer Science topics?: Discrete Mathematics CS Chapters 1.1 Propositional Logic 1.2 Propositional Equivalences 1.3 Predicates and Quantifiers 1.4 Nested Quantifiers 1.5 Rules of Inference 1.6 Introduction to Proofs 1.7 Proof Methods and Strategy 2.1 Sets 2.2 Set Operations 2.3 Functions 2.4 Sequences and Summations 3.1 Algorithms 3.2 The Growths of Functions 3.3 Complexity of Algorithms 3.4 The Integers and Division 3.5 Primes and Greatest Common Divisors 3.6 Integers and Algorithms 3.8 Matrices 4.1 Mathematical Induction 4.2 Strong Induction and Well-Ordering 4.3 Recursive Definitions and Structural Induction 4.4 Recursive Algorithms 4.5 Program Correctness 5.1 The Basics of Counting 5.2 The Pigeonhole Principle 5.3 Permutations and Combinations 5.6 Generating Permutations and Combinations 6.1 An Introduction to Discrete Probability 6.4 Expected Value and Variance 7.1 Recurrence Relations 7.3 Divide-and-Conquer Algorithms and Recurrence Relations 7.5 Inclusion-Exclusion 8.1 Relations and Their Properties 8.2 n-ary Relations and Their Applications 8.3 Representing Relations 8.5 Equivalence Relations 9.1 Graphs and Graph Models 9.2 Graph Terminology and Special Types of Graphs 9.3 Representing Graphs and Graph Isomorphism 9.4 Connectivity 9.5 Euler and Hamilton Ptahs 10.1 Introduction to Trees 10.2 Application of Trees 10.3 Tree Traversal 11.1 Boolean Functions 11.2 Representing Boolean Functions 11.3 Logic Gates 11.4 Minimization of Circuits 12.1 Language and Grammars 12.2 Finite-State Machines with Output 12.3 Finite-State Machines with No Output 12.4 Language Recognition 12.5 Turing Machines Precalculus Chapters R.1 The Real-Number System R.2 Integer Exponents, Scientific Notation, and Order of Operations R.3 Addition, Subtraction, and Multiplication of Polynomials R.4 Factoring R.5 Rational Expressions R.6 Radical Notation and Rational Exponents R.7 The Basics of Equation Solving 1.1 Functions, Graphs, Graphers 1.2 Linear Functions, Slope, and Applications 1.3 Modeling: Data Analysis, Curve Fitting, and Linear Regression 1.4 More on Functions 1.5 Symmetry and Transformations 1.6 Variation and Applications 1.7 Distance, Midpoints, and Circles 2.1 Zeros of Linear Functions and Models 2.2 The Complex Numbers 2.3 Zeros of Quadratic Functions and Models 2.4 Analyzing Graphs of Quadratic Functions 2.5 Modeling: Data Analysis, Curve Fitting, and Quadratic Regression 2.6 Zeros and More Equation Solving 2.7 Solving Inequalities 3.1 Polynomial Functions and Modeling 3.2 Polynomial Division; The Remainder and Factor Theorems 3.3 Theorems about Zeros of Polynomial Functions 3.4 Rational Functions 3.5 Polynomial and Rational Inequalities 4.1 Composite and Inverse Functions 4.2 Exponential Functions and Graphs 4.3 Logarithmic Functions and Graphs 4.4 Properties of Logarithmic Functions 4.5 Solving Exponential and Logarithmic Equations 4.6 Applications and Models: Growth and Decay 5.1 Systems of Equations in Two Variables 5.2 System of Equations in Three Variables 5.3 Matrices and Systems of Equations 5.4 Matrix Operations 5.5 Inverses of Matrices 5.6 System of Inequalities and Linear Programming 5.7 Partial Fractions 6.1 The Parabola 6.2 The Circle and Ellipse 6.3 The Hyperbola 6.4 Nonlinear Systems of Equations

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  • A website hosted on the 1.0.0.0/8 subnet, somewhere on the Internet?

    - by Dave Markle
    Background I'm attempting to demonstrate, using a real-world example, of why someone would not want to configure their internal network on the 1.0.0.0/8 subnet. Obviously it's because this is not designated as private address space. As of 2010, ARIN has apparently allocated 1.0.0.0/8 to APNIC (the Asia-Pacific NIC), who seems to have begun assigning addresses in that subnet, though not in 1.1.0.0/16, 1.0.0.0/16, and others (because these addresses are so polluted by bad network configurations all around the Internet). My Question My question is this: I'd like to find a website that responds on this subnet somewhere and use it as a counter-example, demonstrating to a non-technical user its inaccessibility from an internal network configured on 1.0.0.0/8. Other than writing a program to sniff all ~16 million hosts, looking for a response on port 80, does anyone know of a directory I can use, or even better yet, does anyone know of a site that's configured on this subnet? WHOIS seems to be too general of a search for me at this point...

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  • Power User - archive Outlook mail items into SQL Server

    - by marc_s
    I am looking (and so far not finding any) for a solution to archive e-mail items from my Outlook into SQL Server. My PST is beginning to get really really big, and I'd love to extract my older e-mail into SQL Server in a way so I can still easily find mails if needed. I would prefer SQL Server as the storage medium since I'm familiar with it, and it's rock solid - I don't want to have a collection of PST files or CHM files or anything like that. Does anyone know of such a solution? I'm a power/home user - I can't afford $5'000 enterprise licenses - I need a sub-$100 solution for private use.

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  • tar: How to create a tar file with arbitrary leading directories w/o 'cd'ing to parent dir

    - by Yan
    Say I have a directory of files at /home/user1/dir1 and I want to create a tar with only "dir1" as the leading directory: /dir1/file1 /dir1/file2 I know I can first cd to the directory cd /home/user1/ tar czvf dir1.tar.gz dir1 But when writing scripts, jumping from directory to directory isn't always favorable. I am wondering is there a way to do it with absolute paths without changing current directories? I know I can always create a tar file with absolute paths INSIDE and use --strip-components when extracting but sometimes extra path names are extra private information that you don't want to distribute with your tar files. Thanks!

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  • How can I make a universal construction more efficient?

    - by VF1
    A "universal construction" is a wrapper class for a sequential object that enables it to be linearized (a strong consistency condition for concurrent objects). For instance, here's an adapted wait-free construction, in Java, from [1], which presumes the existence of a wait-free queue that satisfies the interface WFQ (which only requires one-time consensus between threads) and assumes a Sequential interface: public interface WFQ<T> // "FIFO" iteration { int enqueue(T t); // returns the sequence number of t Iterable<T> iterateUntil(int max); // iterates until sequence max } public interface Sequential { // Apply an invocation (method + arguments) // and get a response (return value + state) Response apply(Invocation i); } public interface Factory<T> { T generate(); } // generate new default object public interface Universal extends Sequential {} public class SlowUniversal implements Universal { Factory<? extends Sequential> generator; WFQ<Invocation> wfq = new WFQ<Invocation>(); Universal(Factory<? extends Sequential> g) { generator = g; } public Response apply(Invocation i) { int max = wfq.enqueue(i); Sequential s = generator.generate(); for(Invocation invoc : wfq.iterateUntil(max)) s.apply(invoc); return s.apply(i); } } This implementation isn't very satisfying, however, since it presumes determinism of a Sequential and is really slow. I attempted to add memory recycling: public interface WFQD<T> extends WFQ<T> { T dequeue(int n); } // dequeues only when n is the tail, else assists other threads public interface CopyableSequential extends Sequential { CopyableSequential copy(); } public class RecyclingUniversal implements Universal { WFQD<CopyableSequential> wfqd = new WFQD<CopyableSequential>(); Universal(CopyableSequential init) { wfqd.enqueue(init); } public Response apply(Invocation i) { int max = wfqd.enqueue(i); CopyableSequential cs = null; int ctr = max; for(CopyableSequential csq : wfq.iterateUntil(max)) if(--max == 0) cs = csq.copy(); wfqd.dequeue(max); return cs.apply(i); } } Here are my specific questions regarding the extension: Does my implementation create a linearizable multi-threaded version of a CopyableSequential? Is it possible extend memory recycling without extending the interface (perhaps my new methods trivialize the problem)? My implementation only reduces memory when a thread returns, so can this be strengthened? [1] provided an implementation for WFQ<T>, not WFQD<T> - one does exist, though, correct? [1] Herlihy and Shavit, The Art of Multiprocessor Programming.

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  • Machine account authentication on Radius server

    - by O.Shevchenko
    My workstation is under Linux. I have an Active Directory domain controller + Radius server on Windows 2008. I can verify user account 'radius-01' using 'radtest' tool: $ radtest -t pap radius-01 password123 195.234.133.32 1812 password123 Sending Access-Request of id 98 to 195.234.73.2 port 1812 User-Name = "radius-01" User-Password = "password123" NAS-IP-Address = 127.0.1.1 NAS-Port = 1812 rad_recv: Access-Accept packet from host 195.234.133.32 port 1812, id=98, length=84 Framed-MTU = 1344 Framed-Protocol = PPP Service-Type = Framed-User Class = 0x537004f00000013700010200ac1c0... I have joined my Linux PC to Active Directory domain ARB-HRK using Samba: [root@shev-arb]# net ads testjoin Join is OK I can dump machine password: [root@shev-arb]# tdbdump /var/lib/samba/private/secrets.tdb { key(34) = "SECRETS/MACHINE_PASSWORD/ARB-HRK" data(15) = "yGgXJsquRnpT0g\00" } How can i authenticate my machine account on Radius server? Do anybody know any tools for this, like: radtest shev-arb$ yGgXJsquRnpT0g 195.234.133.32 1812 password123 (this command fails)

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  • Building Enterprise Smartphone App &ndash; Part 4: Application Development Considerations

    - by Tim Murphy
    This is the final part in a series of posts based on a talk I gave recently at the Chicago Information Technology Architects Group.  Feel free to leave feedback. Application Development Considerations Now we get to the actual building of your solutions.  What are the skills and resources that will be needed in order to develop a smartphone application in the enterprise? Language Knowledge One of the first things you need to consider when you are deciding which platform language do you either have the most in house skill base or can you easily acquire.  If you already have developers who know Java or C# you may want to use either Android or Windows Phone.  You should also take into consideration the market availability of developers.  If your key developer leaves how easy is it to find a knowledgeable replacement? A second consideration when it comes to programming languages is the qualities exposed by the languages of a particular platform.  How well does that development language and its associated frameworks support things like security and access to the features of the smartphone hardware?  This will play into your overall cost of ownership if you have to create this infrastructure on your own. Manage Limited Resources Everything is limited on a smartphone: battery, memory, processing power, network bandwidth.  When developing your applications you will have to keep your footprint as small as possible in every way.  This means not running unnecessary processes in the background that will drain the battery or pulling more data over the airwaves than you have to.  You also want to keep your on device in as compact a format as possible. Mobile Design Patterns There are a number of design patterns that have either come to life because of smartphone development or have been adapted for this use.  The main pattern in the Windows Phone environment is the MVVM (Model-View-View-Model).  This is great for overall application structure and separation of concerns.  The fun part is trying to keep that separation as pure as possible.  Many of the other patterns may or may not have strict definitions, but some that you need to be concerned with are push notification, asynchronous communication and offline data storage. Real estate is limited on smartphones and even tablets. You are also limited in the type of controls that can be represented in the UI. This means rethinking how you modularize your application. Typing is also much harder to do so you want to reduce this as much as possible.  This leads to UI patterns.  While not what we would traditionally think of as design patterns the guidance each platform has for UI design is critical to the success of your application.  If user find the application difficult navigate they will not use it. Development Process Because of the differences in development tools required, test devices and certification and deployment processes your teams will need to learn new way of working together.  This will include the need to integrate service contracts of back-end systems with mobile applications.  You will also want to make sure that you present consistency across different access points to corporate data.  Your web site may have more functionality than your smartphone application, but it should have a consistent core set of functionality.  This all requires greater communication between sub-teams of your developers. Testing Process Testing of smartphone apps has a lot more to do with what happens when you lose connectivity or if the user navigates away from your application. There are a lot more opportunities for the user or the device to perform disruptive acts.  This should be your main testing concentration aside from the main business requirements.  You will need to do things like setting the phone to airplane mode and seeing what the application does in order to weed out any gaps in your handling communication interruptions. Need For Outside Experts Since this is a development area that is new to most companies the need for experts is a lot greater. Whether these are consultants, vendor representatives or just development community forums you will need to establish expert contacts. Nothing is more dangerous for your project timelines than a lack of knowledge.  Make sure you know who to call to avoid lengthy delays in your project because of knowledge gaps. Security Security has to be a major concern for enterprise applications. You aren't dealing with just someone's game standings. You are dealing with a companies intellectual property and competitive advantage. As such you need to start by limiting access to the application itself.  Once the user is in the app you need to ensure that the data is secure at all times.  This includes both local storage and across the wire.  This means if a platform doesn’t natively support encryption for these functions you will need to find alternatives to secure your data.  You also need to keep secret (encryption) keys obfuscated or locked away outside of the application. People can disassemble the code otherwise and break your encryption. Offline Capabilities As we discussed earlier one your biggest concerns is not having connectivity.  Because of this a good portion of your code may be dedicated to handling loss of connection and reconnection situations.  What do you do if you lose the network?  Back up all your transactions and store of any supporting data so that operations can continue off line. In order to support this you will need to determine the available flat file or local data base capabilities of the platform.  Any failed transactions will need to support a retry mechanism whether it is automatic or user initiated.  This also includes your services since they will need to be able to roll back partially completed transactions.  What ever you do, don’t ignore this area when you are designing your system. Deployment Each platform has different deployment capabilities. Some are more suited to enterprise situations than others. Apple's approach is probably the most mature at the moment. Prior to the current generation of smartphone platforms it would have been Windows CE. Windows Phone 7 has the limitation that the app has to be distributed through the same network as public facing applications. You mark them as private which means that they are only accessible by a direct URL. Unfortunately this does not make them undiscoverable (although it is very difficult). This will change with Windows Phone 8 where companies will be able to certify their own applications and distribute them.  Given this Windows Phone applications need to be more diligent with application access in order to keep them restricted to the company's employees. My understanding of the Android deployment schemes is that it is much less standardized then either iOS or Windows Phone. Someone would have to confirm or deny that for me though since I have not yet put the time into researching this platform further. Given my limited exposure to the iOS and Android platforms I have not been able to confirm this, but there are varying degrees of user involvement to install and keep applications updated. At one extreme the user just goes to a website to do the install and in other case they may need to download files and perform steps to install them. Future Bluetooth Today we use Bluetooth for keyboards, mice and headsets.  In the future it could be used to interrogate car computers or manufacturing systems or possibly retail machines by service techs.  This would open smartphones to greater use as a almost a Star Trek Tricorder.  You would get you all your data as well as being able to use it as a universal remote for just about any device or machine. Better corporation controlled deployment At least in the Windows Phone world the upcoming release of Windows Phone 8 will include a private certification and deployment option that is currently not available with Windows Phone 7 (Mango). We currently have to run the apps through the Marketplace certification process and use a targeted distribution method. Platform independent approaches HTML5 and JavaScript with Web Service has become a popular topic lately for not only creating flexible web site, but also creating cross platform mobile applications.  I’m not yet convinced that this lowest common denominator approach is viable in most cases, but it does have it’s place and seems to be growing.  Be sure to keep an eye on it. Summary From my perspective enterprise smartphone applications can offer a great competitive advantage to many companies.  They are not cheap to build and should be approached cautiously.  Understand the factors I have outlined in this series, do you due diligence and see if there is a portion of your business that can benefit from the mobile experience. del.icio.us Tags: Architecture,Smartphones,Windows Phone,iOS,Android

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  • How to remove a box2d body when collision happens?

    - by Ayham
    I’m still new to java and android programming and I am having so much trouble Removing an object when collision happens. I looked around the web and found that I should never handle removing BOX2D bodies during collision detection (a contact listener) and I should add my objects to an arraylist and set a variable in the User Data section of the body to delete or not and handle the removing action in an update handler. So I did this: First I define two ArrayLists one for the faces and one for the bodies: ArrayList<Sprite> myFaces = new ArrayList<Sprite>(); ArrayList<Body> myBodies = new ArrayList<Body>(); Then when I create a face and connect that face to its body I add them to their ArrayLists like this: face = new AnimatedSprite(pX, pY, pWidth, pHeight, this.mBoxFaceTextureRegion); Body BoxBody = PhysicsFactory.createBoxBody(mPhysicsWorld, face, BodyType.DynamicBody, objectFixtureDef); mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(face, BoxBody, true, true)); myFaces.add(face); myBodies.add(BoxBody); now I add a contact listener and an update handler in the onloadscene like this: this.mPhysicsWorld.setContactListener(new ContactListener() { private AnimatedSprite face2; @Override public void beginContact(final Contact pContact) { } @Override public void endContact(final Contact pContact) { } @Override public void preSolve(Contact contact,Manifold oldManifold) { } @Override public void postSolve(Contact contact,ContactImpulse impulse) { } }); scene.registerUpdateHandler(new IUpdateHandler() { @Override public void reset() { } @Override public void onUpdate(final float pSecondsElapsed) { } }); My plan is to detect which two bodies collided in the contact listener by checking a variable from the user data section of the body, get their numbers in the array list and finally use the update handler to remove these bodies. The questions are: Am I using the arraylist correctly? How to add a variable to the User Data (the code please). I tried removing a body in this update handler but it still throws me NullPointerException , so what is the right way to add an update handler and where should I add it. Any other advices to do this would be great. Thanks in advance.

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  • When I shoot from a gun while walking, the bullet is off the center, but when stand still it's fine

    - by Vlad1k
    I am making a small project in Unity, and whenever I walk with the gun and shoot at the same time, the bullets seem to curve and shoot off 2-3 CMs from the center. When I stand still this doesn't happen. This is my main Javascript code: @script RequireComponent(AudioSource) var projectile : Rigidbody; var speed = 500; var ammo = 30; var fireRate = 0.1; private var nextFire = 0.0; function Update() { if(Input.GetButton ("Fire1") && Time.time > nextFire) { if(ammo != 0) { nextFire = Time.time + fireRate; var clone = Instantiate(projectile, transform.position, transform.root.rotation); clone.velocity = transform.TransformDirection(Vector3 (0, 0, speed)); ammo = ammo - 1; audio.Play(); } else { } } } I assume that these two lines need to be tweaked: var clone = Instantiate(projectile, transform.position, transform.root.rotation); clone.velocity = transform.TransformDirection(Vector3 (0, 0, speed)); Thanks in advanced, and please remember that I just started Unity, and I might have a difficult time understanding some things. Thanks!

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  • putty pageant - forget keys after period of inactivity

    - by pQd
    in the environment where windows client computers are used to run putty to connect to multiple linux servers i'm considering moving away from password based authentication and using public/private key pairs with pass-phrases. using ssh-agent would be nice, but at the same time i'd like it to 'forget' the pass-phrases after given period of inactivity. it seems that putty's pageant does not provide such feature; what would you suggest as alternative? solutions that i'm considering: patching pageant code [might be tricky, code is probably quite rusty and project - sadly - stagnant] writing small custom application using GetLastInputInfo and killing pageant if the machine was idle for more than let's say 15 minutes [ yes, there'll be separate policy for locking the desktops as well ] using alternative ssh client and ssh agent. any suggestions? thanks!

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  • SFX Played Once per Collision or Hit

    - by David Dimalanta
    I have a question about using Box2D (engine for LibGDX used to make realistic physics). I observed on the code that I've made for the physics here below: @Override public boolean touchUp(int screenX, int screenY, int pointer, int button) { // TODO Touch Up Event if(is_Next_Fruit_Touched) { BodyEditorLoader Fruit_Loader = new BodyEditorLoader(Gdx.files.internal("Shape_Physics/Fruity Physics.json")); Fruit_BD.type = BodyType.DynamicBody; Fruit_BD.position.set(x, y); FixtureDef Fruit_FD = new FixtureDef(); // --> Allows you to make the object's physics. Fruit_FD.density = 1.0f; Fruit_FD.friction = 0.7f; Fruit_FD.restitution = 0.2f; MassData mass = new MassData(); mass.mass = 5f; Fruit_Body[n] = world.createBody(Fruit_BD); Fruit_Body[n].setActive(true); // --> Let your dragon fall. Fruit_Body[n].setMassData(mass); Fruit_Body[n].setGravityScale(1.0f); System.out.println("Eggs... " + n); Fruit_Loader.attachFixture(Fruit_Body[n], Body, Fruit_FD, Fruit_IMG.getWidth()); Fruit_Origin = Fruit_Loader.getOrigin(Body, Fruit_IMG.getWidth()).cpy(); is_Next_Fruit_Touched = false; up = y; Gdx.app.log("Initial Y-coordinate", "Y at " + up); //Once it's touched, the next fruit will set to drag. if(n < 50) { n++; }else{ System.exit(0); } } return true; } Now, I'm thinking which part o line should I implement for the sound effects. My objectives to make SFX played once for every collision (Or should I say "SFX played once per collision"?) on the following: SFX played once if they hit on the objects of its kind. (e.g. apple vs. apple) SFX played once on a different sound when it hit on the ground. (e.g. apple land on the mud) Take note that I'm using Box2D for the Java programming version thanks to LibGDX via Box2D engine and I edited the physics body using Physics Body Editor before I implement it to code. I tried to check every available methods for body, fixture definition, or body definition to code for the SFX when hit but it seems only for the gravity and weight. Is there possibly available on the document for SFX played when collision happens if possible?

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  • How to implement smart card authentication with a .NET Fat client?

    - by John Nevermore
    I know very little about smart card authentication in general so please point out or correct me if anything below doesn't make sense. Lets say i have: A Certificate Authority "X"-s smart card (non-exportable private key) Drivers for that smart card written in C A smart card reader CA-s authentication OCSP web service A requirement to implement user authentication in a .NET fat client application via a smart card, that was given out by the CA "X". I tried searching info on the web but no prevail. What would the steps be ? My first thought was: Set up a web service, that would allow saving of (for example) scores of a ping pong game for each user. Each time someone tries to submit a score via the client application, he can only do so by inserting the smart card into the reader. Then the public key is read from the smart card by native c calls through .NET and sent to my custom web service, which in return uses the CA-s authentication OCSP web service to prove the validity of the public key/public certificate (?). If the public key is okay and valid, encrypt a random sequence of bytes with the public key and send it to the client application. If the client application sends back the correctly decrypted random sequence of bytes along with the score of the ping pong game, then the score is saved in the database for the given user. My question is, is this the correct way to do it ? What else should i know about smart card authentication ?

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  • Script/tool to import series of snapshots, each being a new edition, into GIT, populating source tree?

    - by Rob
    I've developed code locally and taken a fairly regular snapshot whenever I reach a significant point in development, e.g. a working build. So I have a long-ish list of about 40 folders, each folder being a snapshot e.g. in ascending date YYYYMMDD order, e.g.:- 20100523 20100614 20100721 20100722 20100809 20100901 20101001 20101003 20101104 20101119 20101203 20101218 20110102 I'm looking for a script to import each of these snapshots into GIT. The end result being that the latest code is the same as the last snapshot, and other editions are accessible and are as numbered. Some other requirements: that the latest edition is not cumulative of the previous snapshots, i.e., files that appeared in older snapshots but which don't appear in later ones (e.g. due to refactoring etc.) should not appear in the latest edition of the code. meanwhile, there should be continuity between files that do persist between snapshots. I would like GIT to know that there are previous editions of these files and not treat them as brand new files within each edition. Some background about my aim: I need to formally revision control this work rather than keep local private snapshot copies. I plan to release this work as open source, so version controlling would be highly recommended I am evaluating some of the current popular version control systems (Subversion and GIT) BUT I definitely need a working solution in GIT as well as subversion. I'm not looking to be persuaded to use one particular tool, I need a solution for each tool I am considering. (I haved posted an answer separately for each tool so separate camps of folks who have expertise in GIT and Subversion will be able to give focused answers on one or the other). The same but separate question for Subversion: Script/tool to import series of snapshots, each being a new revision, into Subversion, populating source tree?

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  • Open a screen session inside a certain user on boot Ubuntu Server Linux

    - by Pez Cuckow
    I currently have a private server which I test my web apps on which runs Ubuntu Server 10.04 I also host a few game servers (rather than having wasted CPU time :-D) for some of my friends. These game servers I run in the game user account and each one has it's own screen session (so friends can ssh in and reboot the game server etc...). For example screen -R l4d2 runs ./start in the L4D2 folder. However if I reboot the server (which I have to do occasionally) all these sessions close and I have to manually create all the screen sessions and run the required games within them. Is there a way to set these screen sessions as Daemons or services or just boot on server start so they restart themselves on server reboot? I hope I have made my question easy to understand but feel free to ask questions! Many thanks,

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  • Hijacking ASP.NET Sessions

    - by Ricardo Peres
    So, you want to be able to access other user’s session state from the session id, right? Well, I don’t know if you should, but you definitely can do that! Here is an extension method for that purpose. It uses a bit of reflection, which means, it may not work with future versions of .NET (I tested it with .NET 4.0/4.5). 1: public static class HttpApplicationExtensions 2: { 3: private static readonly FieldInfo storeField = typeof(SessionStateModule).GetField("_store", BindingFlags.NonPublic | BindingFlags.Instance); 4:  5: public static ISessionStateItemCollection GetSessionById(this HttpApplication app, String sessionId) 6: { 7: var module = app.Modules["Session"] as SessionStateModule; 8:  9: if (module == null) 10: { 11: return (null); 12: } 13:  14: var provider = storeField.GetValue(module) as SessionStateStoreProviderBase; 15:  16: if (provider == null) 17: { 18: return (null); 19: } 20:  21: Boolean locked; 22: TimeSpan lockAge; 23: Object lockId; 24: SessionStateActions actions; 25:  26: var data = provider.GetItem(HttpContext.Current, sessionId.Trim(), out locked, out lockAge, out lockId, out actions); 27:  28: if (data == null) 29: { 30: return (null); 31: } 32:  33: return (data.Items); 34: } 35: } As you can see, it extends the HttpApplication class, that is because we need to access the modules collection, for the Session module. Use with care!

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  • NetBeans IDE 7.3 Knows Null

    - by Geertjan
    What's the difference between these two methods, "test1" and "test2"? public int test1(String str) {     return str.length(); } public int test2(String str) {     if (str == null) {         System.err.println("Passed null!.");         //forgotten return;     }     return str.length(); } The difference, or at least, the difference that is relevant for this blog entry, is that whoever wrote "test2" apparently thinks that the variable "str" may be null, though did not provide a null check. In NetBeans IDE 7.3, you see this hint for "test2", but no hint for "test1", since in that case we don't know anything about the developer's intention for the variable and providing a hint in that case would flood the source code with too many false positives:  Annotations are supported in understanding how a piece of code is intended to be used. If method return types use @Nullable, @NullAllowed, @CheckForNull, the value is considered to be "strongly possible to be null", as well as if the variable is tested to be null, as shown above. When using @NotNull, @NonNull, @Nonnull, the value is considered to be non-null. (The exact FQNs of the annotations are ignored, only simple names are checked.) Here are examples showing where the hints are displayed for the non-null hints (the "strongly possible to be null" hints are not shown below, though you can see one of them in the screenshot above), together with a comment showing what is shown when you hover over the hint: There isn't a "one size fits all" refactoring for these various instances relating to null checks, hence you can't do an automated refactoring across your code base via tools in NetBeans IDE, as shown yesterday for class member reordering across code bases. However, you can, instead, go to Source | Inspect and then do a scan throughout a scope (e.g., current file/package/project or combinations of these or all open projects) for class elements that the IDE identifies as potentially having a problem in this area: Thanks to Jan Lahoda, who reports that this currently also works in NetBeans IDE 7.3 dev builds for fields but that may need to be disabled since right now too many false positives are returned, for help with the info above and any misunderstandings are my own fault!

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  • Why enumerator structs are a really bad idea (redux)

    - by Simon Cooper
    My previous blog post went into some detail as to why calling MoveNext on a BCL generic collection enumerator didn't quite do what you thought it would. This post covers the Reset method. To recap, here's the simple wrapper around a linked list enumerator struct from my previous post (minus the readonly on the enumerator variable): sealed class EnumeratorWrapper : IEnumerator<int> { private LinkedList<int>.Enumerator m_Enumerator; public EnumeratorWrapper(LinkedList<int> linkedList) { m_Enumerator = linkedList.GetEnumerator(); } public int Current { get { return m_Enumerator.Current; } } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { return m_Enumerator.MoveNext(); } public void Reset() { ((System.Collections.IEnumerator)m_Enumerator).Reset(); } public void Dispose() { m_Enumerator.Dispose(); } } If you have a look at the Reset method, you'll notice I'm having to cast to IEnumerator to be able to call Reset on m_Enumerator. This is because the implementation of LinkedList<int>.Enumerator.Reset, and indeed of all the other Reset methods on the BCL generic collection enumerators, is an explicit interface implementation. However, IEnumerator is a reference type. LinkedList<int>.Enumerator is a value type. That means, in order to call the reset method at all, the enumerator has to be boxed. And the IL confirms this: .method public hidebysig newslot virtual final instance void Reset() cil managed { .maxstack 8 L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator<int32> EnumeratorWrapper::m_Enumerator L_0007: box [System]System.Collections.Generic.LinkedList`1/Enumerator<int32> L_000c: callvirt instance void [mscorlib]System.Collections.IEnumerator::Reset() L_0011: nop L_0012: ret } On line 0007, we're doing a box operation, which copies the enumerator to a reference object on the heap, then on line 000c calling Reset on this boxed object. So m_Enumerator in the wrapper class is not modified by the call the Reset. And this is the only way to call the Reset method on this variable (without using reflection). Therefore, the only way that the collection enumerator struct can be used safely is to store them as a boxed IEnumerator<T>, and not use them as value types at all.

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  • Dovecot and StartSSL problems with issuer

    - by knoim
    I am using dovecot (1) and trying to get my StartSSL certificate running. ssl_key_file points to my private key I tried pointing ssl_cert_file to my public key, with and without using the class1 certificate from http://www.startssl.com/certs/sub.class1.server.ca.pem as ssl_ca_file aswell as combing them with cat publickey sub.class1.server.ca.pem chained My mail client keeps telling me the certificate has no issuer, but doing openssl x509 on my public certificate tells me it is C=IL, O=StartCom Ltd., OU=Secure Digital Certificate Signing, CN=StartCom Class 1 Primary Intermediate Server CA My option for the CSR were: openssl req -new -newkey rsa:4096 -nodes Dovecot's log doesn't mention any problems. EDIT: Doesn't seem to be a problem with dovecot. I am having the same problem with postfix. openssl verify gives me the same error.

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  • Can I disable Pam Loginuid? Can I find out options used to configure kernel?

    - by dunxd
    I am getting a lot of the following types of error in my secure log on a CentOS 5.4 server: crond[10445]: pam_loginuid(crond:session): set_loginuid failed opening loginuid sshd[10473]: pam_loginuid(sshd:session): set_loginuid failed opening loginuid I've seen discussion of this being caused when using a non-standard kernel without the correct CONFIG_AUDIT and CONFIG_AUDITSYSCALL options set. Where this is the case, it is advised to comment out some lines in the pam.d config files. I am running a Virtual Private Server where I need to use the kernel provided by the supplier. Is there a way to find out what options they used to configure the kernel? I want to verify if the above is the cause. If this turns out not to be the cause, what are the risk of disabling pam_loginuid for crond and sshd?

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  • Setting up WAMP to run on a LAN

    - by Steve
    I've installed WAMP on a Windows 7 PC, and it is running fine locally, as localhost. I want PCs on the LAN to be able to view the local server. When they load my PC's IP address in their browser, they receive a "You don't have permission to access / on this server" error. I followed this guide, but the issue remains. To recap: I've added an inbound exception to Windows Firewall for port 80 for Private and Domain connections. I've edited Apache's httpd.conf to include: Listen 80 Listen 192.168.0.5:80 < Directory "c:/wamp/www/wordpress/" allow from all < /Directory I've edited httpd-vhosts.conf to include: < VirtualHost 192.168.0.5:80 DocumentRoot "C:/wamp/www/wordpress" < /VirtualHost Any ideas?

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  • Mounting Gluster Volumes

    - by Roman Newaza
    I have created Hosted Zone with 2 IP addresses of Gluster Cluster, both IP are returned by dig. After mounting Gluster, I cannot ls mount point as it takes long time. mount shows me it's mounted, but df doesn't. Finally, I have this: ls: cannot access /mnt/storage: Transport endpoint is not connected. But if I mount it with the one of the IP, no problem - volume contents is accessible OS: Ubuntu 11.10 GlusterFS: 3.2.6 Log: http://pastie.org/private/2jgp4h1hnqgzych3djtg I have can telnet storage from client - ports are open.

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  • Take care to unhook Anonymous Delegates

    - by David Vallens
    Anonymous delegates are great, they elimiante the need for lots of small classes that just pass values around, however care needs to be taken when using them, as they are not automatically unhooked when the function you created them in returns. In fact after it returns there is no way to unhook them. Consider the following code.   using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Diagnostics; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { SimpleEventSource t = new SimpleEventSource(); t.FireEvent(); FunctionWithAnonymousDelegate(t); t.FireEvent(); } private static void FunctionWithAnonymousDelegate(SimpleEventSource t) { t.MyEvent += delegate(object sender, EventArgs args) { Debug.WriteLine("Anonymous delegate called"); }; t.FireEvent(); } } public class SimpleEventSource { public event EventHandler MyEvent; public void FireEvent() { if (MyEvent == null) { Debug.WriteLine("Attempting to fire event - but no ones listening"); } else { Debug.WriteLine("Firing event"); MyEvent(this, EventArgs.Empty); } } } } If you expected the anonymous delegates do die with the function that created it then you would expect the output Attempting to fire event - but no ones listeningFiring eventAnonymous delegate calledAttempting to fire event - but no ones listening However what you actually get is Attempting to fire event - but no ones listeningFiring eventAnonymous delegate calledFiring eventAnonymous delegate called In my example the issue is just slowing things down, but if your delegate modifies objects, then you could end up with dificult to diagnose bugs. A solution to this problem is to unhook the delegate within the function var myDelegate = delegate(){Console.WriteLine("I did it!");}; MyEvent += myDelegate; // .... later MyEvent -= myDelegate;

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  • Routing and Remote access rule not being applied internally (Windows SBS)

    - by Tim Saunders
    Hi, I have a Microsoft Small Business Server. I have pointed an external domain name to the external fixed IP address for the server. In routing and remote access I have defined a service for our subversion server as follows: Incoming port: 8443 Private address: 192.168.10.5 Outgoing port: 8443 192.168.10.5 is our development server, not the SBS (which is at 192.168.10.1) This rule works correctly if I am not on our internal network. However if I am on the internal network this rule does not get applied. What can I do/set so this rule is applied both internally and externally (so users with laptops et, don't keep having to change the URL by which they access the subversion server) Not sure what other info you may need, so please let me know if more details are required. T

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  • How can I flush my ssh keys on power management activity?

    - by Sam Halicke
    Hi all, Using ssh-agent and private keys per the usual. Everything's working as normal. My question regards best practices on flushing keys from ssh-add on activity like sleep, suspend, hibernate, etc. I thought about writing a simple wrapper around those commands, but then wondered if are they even called? Or does the kernel initiate this activity directly? Are the PM utilities strictly userland? I would like this additional layer of security beyond locking my screen, etc. and was wondering if anyone else had solved this elegantly or has best practices to recommend. Thanks.

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  • Failed to fetch *.deb Size mismatch, then packages with unmet dependencies [solved]

    - by user113907
    I recently bought the wonderfully looking and reviewed Amnesia The Dark Descent and I'm trying to install it. The first time I tried to download it, I had to stop in the middle of the download (may have broken something). The second time I tried to download, at the end of the download it gave me the following error: Failed to fetch https://private-ppa.launchpad.net/commercial-ppa-uploaders/amnesia/ubuntu/pool/main/a/amnesia/amnesia_1.2.1-0ubuntu2_i386.deb Size mismatch Now, whenever I try to download it, it gives me this error: The following packages have unmet dependencies: amnesia: Depends: libalut0 (>= 1.0.1) but it is not going to be installed Depends: libc6 (>= 2.4) but 2.15-0ubuntu10.3 is to be installed Depends: libfontconfig1 (>= 2.8.0) but 2.8.0-3ubuntu9.1 is to be installed Depends: libfreetype6 (>= 2.2.1) but 2.4.8-1ubuntu2 is to be installed Depends: libgcc1 (>= 1:4.1.1) but 1:4.6.3-1ubuntu5 is to be installed Depends: libopenal1 (>= 1:1.13) but 1:1.13-4ubuntu3 is to be installed Depends: libsdl1.2debian (>= 1.2.10-1) but 1.2.14-6.4ubuntu3 is to be installed Depends: libstdc++6 (>= 4.1.1) but 4.6.3-1ubuntu5 is to be installed Depends: libxft2 (> 2.1.1) but 2.2.0-3ubuntu2 is to be installed Depends: zlib1g (>= 1:1.1.4) but 1:1.2.3.4.dfsg-3ubuntu4 is to be installed I already searched the net and ran a few command line commands. Ex: sudo dpkg --configure -a sudo apt-get install -f Or configure the software packages to download from Main instead of the local UK server. But I'm really not figuring out a solution. I have a fresh install of the latest LTS (12.04). The only non-standard thing so far is that I installed gnome-shell (?) because I really can't stand Unity. Help would be much appreciated. I am currently more than entertained enough with World of Goo and Command & Conquer, but I will want to play Amnesia in the close future.

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