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  • Shouldn't storage classes be taught early in a C class or book?

    - by Adam Mendoza
    Shouldn't storage classes be taught early in a C class or book? I notice that a lot of books, even some of the better ones, covert it toward and end of the book and some books just add it as an appendix. I would teach it together with variables. This is so foundational and I think unfortunately many do not make it that far in a book. Now that auto has a different meaning (vs being optional) it may confuse people that didn't realize it has always been there. for example: C Programming: A Modern Approach 18.2 Storage Classes 401 Properties of Variables 401 The auto Storage Class 402 The static Storage Class 403 The extern Storage Class 404 The register Storage Class 405 The Storage Class of a Function 406 Summary 407

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  • Tunneling a public IP to a remote machine

    - by Jim Paris
    I have a Linux server A with a block of 5 public IP addresses, 8.8.8.122/29. Currently, 8.8.8.122 is assigned to eth0, and 8.8.8.123 is assigned to eth0:1. I have another Linux machine B in a remote location, behind NAT. I would like to set up an tunnel between the two so that B can use the IP address 8.8.8.123 as its primary IP address. OpenVPN is probably the answer, but I can't quite figure out how to set things up (topology subnet or topology p2p might be appropriate. Or should I be using Ethernet bridging?). Security and encryption is not a big concern at this point, so GRE would be fine too -- machine B will be coming from a known IP address and can be authenticated based on that. How can I do this? Can anyone suggest an OpenVPN config, or some other approach, that could work in this situation? Ideally, it would also be able to handle multiple clients (e.g. share all four of spare IPs with other machines), without letting those clients use IPs to which they are not entitled.

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  • How should I organise classes for a space simulator?

    - by Peteyslatts
    I have pretty much taught myself everything I know about programming, so while I know how to teach myself (books, internet and reading API's), I'm finding that there hasn't been a whole lot in the way of good programming. I am finishing up learning the basics of XNA and I want to create a space simulator to test my knowledge. This isn't a full scale simulator, but just something that covers everything I learned. It's also going to be modular so I can build on it, after I get the basics down. One of the early features I want to implement is AI. And I want to take this into account as I'm designing my classes so I can minimize rewriting code. So my question: How should I design ship classes so that both the player and AI can use them? The only idea I have so far is: Create a ship class that contains stats, models, textures, collision data etc. The player and AI would then have the data for position, rotation, health, etc and would base their status off of the ship stats.

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  • Is it okay to have many Abstract classes in your application?

    - by JoseK
    We initially wanted to implement a Strategy pattern with varying implementations of the methods in a commmon interface. These will get picked up at runtime based on user inputs. As it's turned out, we're having Abstract classes implementing 3 - 5 common methods and only one method left for a varying implementation i.e. the Strategy. Update: By many abstract classes I mean there are 6 different high level functionalities i.e. 6 packages , and each has it's Interface + AbstractImpl + (series of Actual Impl). Is this a bad design in any way? Any negative views in terms of later extensibility - I'm preparing for a code/design review with seniors.

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  • Why is it good to split a program into multiple classes?

    - by user1276078
    I'm still a student in high school (entering 10th grade), and I have yet to take an actual computer course in school. Everything I've done so far is through books. Those books have taught me concepts such as inheritance, but how does splitting a program into multiple classes help? The books never told me. I'm asking this mainly because of a recent project. It's an arcade video game, sort of like a flash game as some people have said (although I have no idea what a flash game is). The thing is, it's only one class. It works perfectly fine (a little occasional lag however) with just one class. So, I'm just asking how splitting it into multiple classes would help it. This project was in JAVA and I am the only person working on it, for the record.

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  • How to make sure clients update their browser cache when my website is updated?

    - by user64204
    I am using the HTTP 1.1 Cache-Control header to implement client-side caching. Since I update my website only once a month I would like the CSS and JS files to be cached for 30 days with Cache-Control: max-age=2592000. The problem is that the 30-day period defined by Cache-Control doesn't coincide with the website update cycle, it starts from the moment the users visit the site and ends 30 days later, which means an update could occur in the meantime and users would be running with outdated content for a while, which could break the rendering of the website if for instance the HTML and CSS no longer match. How can I perform client-side caching of content for periods of several days but somehow get users to refresh their CSS/JS files after the website has been updated? One solution I could think of is that if website updates can be schedule, the max-age returned by the server could be decreased every day accordingly so that no matter when people visit the website, the end of caching period would coincide with the update of the website, but changing the server configuration every day goes against one of my sysadmin principles (once it's running, don't touch it).

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  • Is there a pattern to restrict which classes can update another class?

    - by Mike
    Say I have a class ImportantInfo with a public writable property Data. Many classes will read this property but only a few will ever set it. Basically, if you want to update Data you should really know what you're doing. Is there a pattern I could use to make this explicit other than by documenting it? For example, some way to enforce that only classes that implement IUpdateImportantData can do it (this is just an example)? I'm not talking about security here, but more of a "hey, are you sure you want to do that?" kind of thing.

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  • Problem with GCC calling static templates functions in templated parent class.

    - by Adisak
    I have some code that compiles and runs on MSVC++ but will not compile on GCC. I have made a test snippet that follows. My goal was to move the static method from BFSMask to BFSMaskSized. Can someone explain what is going on with the errors (esp. the weird 'operator<' error)? Thank you. In the case of both #defines are 0, then the code compiles on GCC. #define DOESNT_COMPILE_WITH_GCC 0 #define FUNCTION_IN_PARENT 0 I get errors if I change either #define to 1. Here are the errors I see. #define DOESNT_COMPILE_WITH_GCC 0 #define FUNCTION_IN_PARENT 1 Test.cpp: In static member function 'static typename Snapper::BFSMask<T>::T_Parent::T_SINT Snapper::BFSMask<T>::Create_NEZ(TCMP)': Test.cpp(492): error: 'CreateMaskFromHighBitSized' was not declared in this scope #define DOESNT_COMPILE_WITH_GCC 1 #define FUNCTION_IN_PARENT 0 Test.cpp: In static member function 'static typename Snapper::BFSMask<T>::T_Parent::T_SINT Snapper::BFSMask<T>::Create_NEZ(TCMP) [with TCMP = int, T = int]': Test.cpp(500): instantiated from 'TVAL Snapper::BFWrappedInc(TVAL, TVAL, TVAL) [with TVAL = int]' Test.cpp(508): instantiated from here Test.cpp(490): error: invalid operands of types '<unresolved overloaded function type>' and 'unsigned int' to binary 'operator<' #define DOESNT_COMPILE_WITH_GCC 1 #define FUNCTION_IN_PARENT 1 Test.cpp: In static member function 'static typename Snapper::BFSMask<T>::T_Parent::T_SINT Snapper::BFSMask<T>::Create_NEZ(TCMP) [with TCMP = int, T = int]': Test.cpp(500): instantiated from 'TVAL Snapper::BFWrappedInc(TVAL, TVAL, TVAL) [with TVAL = int]' Test.cpp(508): instantiated from here Test.cpp(490): error: invalid operands of types '<unresolved overloaded function type>' and 'unsigned int' to binary 'operator<' Here is the code namespace Snapper { #define DOESNT_COMPILE_WITH_GCC 0 #define FUNCTION_IN_PARENT 0 // MASK TYPES // NEZ - Not Equal to Zero #define BFSMASK_NEZ(A) ( ( A ) | ( 0 - A ) ) #define BFSELECT_MASK(MASK,VTRUE,VFALSE) ( ((MASK)&(VTRUE)) | ((~(MASK))&(VFALSE)) ) template<typename TVAL> TVAL BFSelect_MASK(TVAL MASK,TVAL VTRUE,TVAL VFALSE) { return(BFSELECT_MASK(MASK,VTRUE,VFALSE)); } //----------------------------------------------------------------------------- // Branch Free Helpers template<int BYTESIZE> struct BFSMaskBase {}; template<> struct BFSMaskBase<2> { typedef UINT16 T_UINT; typedef SINT16 T_SINT; }; template<> struct BFSMaskBase<4> { typedef UINT32 T_UINT; typedef SINT32 T_SINT; }; template<int BYTESIZE> struct BFSMaskSized : public BFSMaskBase<BYTESIZE> { static const int SizeBytes = BYTESIZE; static const int SizeBits = SizeBytes*8; static const int MaskShift = SizeBits-1; typedef typename BFSMaskBase<BYTESIZE>::T_UINT T_UINT; typedef typename BFSMaskBase<BYTESIZE>::T_SINT T_SINT; #if FUNCTION_IN_PARENT template<int N> static T_SINT CreateMaskFromHighBitSized(typename BFSMaskBase<N>::T_SINT inmask); #endif }; template<typename T> struct BFSMask : public BFSMaskSized<sizeof(T)> { // BFSMask = -1 (all bits set) typedef BFSMask<T> T_This; // "Import" the Parent Class typedef BFSMaskSized<sizeof(T)> T_Parent; typedef typename T_Parent::T_SINT T_SINT; #if FUNCTION_IN_PARENT typedef T_Parent T_MaskGen; #else typedef T_This T_MaskGen; template<int N> static T_SINT CreateMaskFromHighBitSized(typename BFSMaskSized<N>::T_SINT inmask); #endif template<typename TCMP> static T_SINT Create_NEZ(TCMP A) { //ReDefineType(const typename BFSMask<TCMP>::T_SINT,SA,A); //const typename BFSMask<TCMP>::T_SINT cmpmask = BFSMASK_NEZ(SA); const typename BFSMask<TCMP>::T_SINT cmpmask = BFSMASK_NEZ(A); #if DOESNT_COMPILE_WITH_GCC return(T_MaskGen::CreateMaskFromHighBitSized<sizeof(TCMP)>(cmpmask)); #else return(CreateMaskFromHighBitSized<sizeof(TCMP)>(cmpmask)); #endif } }; template<typename TVAL> TVAL BFWrappedInc(TVAL x,TVAL minval,TVAL maxval) { const TVAL diff = maxval-x; const TVAL mask = BFSMask<TVAL>::Create_NEZ(diff); const TVAL incx = x + 1; return(BFSelect_MASK(mask,incx,minval)); } SINT32 currentsnap = 0; SINT32 SetSnapshot() { currentsnap=BFWrappedInc<SINT32>(currentsnap,0,20); return(currentsnap); } }

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  • Xcode 3.2: Build & Analyze never finds any issues

    - by GamingHorror
    I've used the Clang Static Analyzer from the command line before. I wanted to try Xcode's built-in version via Build & Analyze. I never get any negative results even though i specially prepared my code with very obvious issues Clang was always able to point out: // over-releasing an object: [label release]; [label release]; // uninitialized vars, allocating but not freeing an object NSString* str; int number; CCLabel* newLabel = [[CCLabel alloc] initWithString:str fontName:str fontSize:number]; [newLabel setPosition:CGPointZero]; The result is always the same: a green checkbox, no issues. I read that C++ code can cause issues. I'm running this with cocos2d that includes box2d. Could this be a cause? Did anyone get results from Build & Analyze with the cocos2d engine? What else could it be? I also tried enabling the Static Analyzer Build Settings and then Build but the result was the same. I have restarted Xcode, cleaned all targets and emptied Xcode caches to no avail.

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  • Filtering code elements when analyzing source code.

    - by Martin
    Hi everybody, Currently I am making a survey about source code analysis and the thing that puzzles me greatly is what is it that project managers and developers would like to filter when analyzing source code (especially when applying OOP metrics - e.g. skpping insignificant methods and classes during analysis or filtering context-based elements according to the type of project). If you have any suggestions based on yout experience with code analysis I will greatly appreciate if you can share some ideas about filtering of elements. Thanks, Martin

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  • Can ASM method-visitors be used with interfaces?

    - by Olaf Mertens
    I need to write a tool that lists the classes that call methods of specified interfaces. It will be used as part of the build process of a large java application consisting of many modules. The goal is to automatically document the dependencies between certain java modules. I found several tools for dependency analysis, but they don't work on the method level, just for packages or jars. Finally I found ASM, that seems to do what I need. The following code prints the method dependencies of all class files in a given directory: import java.io.*; import java.util.*; import org.objectweb.asm.ClassReader; public class Test { public static void main(String[] args) throws Exception { File dir = new File(args[0]); List<File> classFiles = new LinkedList<File>(); findClassFiles(classFiles, dir); for (File classFile : classFiles) { InputStream input = new FileInputStream(classFile); new ClassReader(input).accept(new MyClassVisitor(), 0); input.close(); } } private static void findClassFiles(List<File> list, File dir) { for (File file : dir.listFiles()) { if (file.isDirectory()) { findClassFiles(list, file); } else if (file.getName().endsWith(".class")) { list.add(file); } } } } import org.objectweb.asm.MethodVisitor; import org.objectweb.asm.commons.EmptyVisitor; public class MyClassVisitor extends EmptyVisitor { private String className; @Override public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) { this.className = name; } @Override public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) { System.out.println(className + "." + name); return new MyMethodVisitor(); } } import org.objectweb.asm.commons.EmptyVisitor; public class MyMethodVisitor extends EmptyVisitor { @Override public void visitMethodInsn(int opcode, String owner, String name, String desc) { String key = owner + "." + name; System.out.println(" " + key); } } The Problem: The code works for regular classes only! If the class file contains an interface, visitMethod is called, but not visitMethodInsn. I don't get any info about the callers of interface methods. Any ideas?

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  • Instance variables vs. class variables in Python

    - by deamon
    I have Python classes, of which I need only one instance at runtime, so it would be sufficient to have the attributes only once per class and not per instance. If there would be more than one instance (what won't happen), all instance should have the same configuration. I wonder which of the following options would be better or more "idiomatic" Python. Class variables: MyController(Controller): path = "something/" childs = [AController, BController] def action(request): pass Instance ariables: MyController(Controller): def __init__(self): self.path = "something/" self.childs = [AController, BController] def action(self, request): pass

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  • Encapsulate update method inside of object or have method which accepts an object to update

    - by Tom
    Hi, I actually have 2 questions related to each other: I have an object (class) called, say MyClass which holds data from my database. Currently I have a list of these objects ( List < MyClass ) that resides in a singleton in a "communal area". I feel it's easier to manage the data this way and I fail to see how passing a class around from object to object is beneficial over a singleton (I would be happy if someone can tell me why). Anyway, the data may change in the database from outside my program and so I have to update the data every so often. To update the list of the MyClass I have a method called say, Update, written in another class which accepts a list of MyClass. This updates all the instances of MyClass in the list. However would it be better instead to encapulate the Update() method inside the MyClass object, so instead I would say foreach(MyClass obj in MyClassList) { obj.update(); } What is a better implementation and why? The update method requires a XML reader. I have written an XML reader class which is basically a wrapper over the standard XML reader the language natively provides which provides application specific data collection. Should the XML reader class be in anyway in the "inheritance path" of the MyClass object - the MyClass objects inherits from the XML reader because it uses a few methods. I can't see why it should. I don't like the idea of declaring an instance of the XML Reader class inside of MyClass and an MyClass object is meant to be a simple "record" from the database and I feel giving it loads of methods, other object instances is a bit messy. Perhaps my XML reader class should be static but C#'s native XMLReader isn't static.? Any comments would be greatly appreciated Thanks Thomas

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  • Returning c_str from a function

    - by user199421
    This is from a small library that I found online: const char* GetHandStateBrief(const PostFlopState* state) { static std::ostringstream out; ... rest of the function ... return out.str().c_str() Now in my code I am doing this: const char *d = GetHandStateBrief(&post); std::cout<< d << std::endl; Now, at first d contained garbage. I then realized that the c string I am getting from the function is destroyed when the function returns because std::ostringstream is allocated on the stack. So I added: return strdup( out.str().c_str()); And now I can get the text I need from the function. I have two questions: 1) Am I understanding this correctly? 2) I later noticed that the ostringstream was was allocated with static storage. Doesn't that mean that the object is supposed to stay in memory until the program terminates? and if so , then why can't I access the string?

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  • Findbugs and comparing

    - by Rob Goodwin
    I recently started using the findbugs static analysis tool in a java build I was doing. The first report came back with loads of High Priority warnings. Being the obsessive type of person, I was ready to go knock them all out. However, I must be missing something. I get most of the warnings when comparing things. Such as the following code: public void setSpacesPerLevel(int value) { if( value >= 0) { ... produces a high priority warning at the if statement that reads. File: Indenter.java, Line: 60, Type: BIT_AND_ZZ, Priority: High, Category: CORRECTNESS Check to see if ((...) & 0) == 0 in sample.Indenter.setSpacesPerLevel(int) I am comparing an int to an int, seems like a common thing. I get quite a few of that type of error with similar simple comparisons. I have alot of other high priority warnings on what appears to be simple code blocks. Am I missing something here? I realize that static analysis can produce false positives, but the errors I am seeing seem too trivial of a case to be a false positive. This one has me scratching my head as well. for(int spaces = 0;spaces < spacesPerLevel;spaces++){... Which gives the following findbugs warning: File: Indenter.java, Line: 160, Type: IL_INFINITE_LOOP, Priority: High, Category: CORRECTNESS There is an apparent infinite loop in sample.Indenter.indent() This loop doesn't seem to have a way to terminate (other than by perhaps throwing an exception). Any ideas? So basically I have a handful of files and 50-60 high priority warnings similar to the ones above. I am using findbugs 1.3.9 and calling it from the findbugs ant task

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  • C++ - Basic WinAPI question

    - by HardCoder1986
    Hello! I am now working on a some sort of a game engine and I had an idea to put everything engine-related into a static library and then link it to my actual problem. Right now I achieved it and actually link that library and every functions seem to work fine, except those, which are windows-related. I have a chunk of code in my library that looks like this: hWnd = CreateWindow(className, "Name", WS_OVERLAPPED | WS_CAPTION | WS_EX_TOPMOST, 0, 0, 800, 600, NULL, NULL, GetModuleHandle(NULL), this); if (hWnd) { ShowWindow(hWnd, SW_NORMAL); UpdateWindow(hWnd); } else { MessageBox(NULL, "Internal program error", "Error", MB_OK | MB_ICONERROR); return; } When this code was not in the library, but in the actual project, it worked fine, created the window and everything was ok. Right now (when I'm linking to my library that contains this code) CreateWindow(...) call returns NULL and GetLastError() returns "Operation succesfully completed" (wtf?). Could anybody help me with this? Is it possible to create a window and display it using a static library call and why could my code fail? Thank you.

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  • Random number generation in MVC applications

    - by SlimShaggy
    What is the correct way of generating random numbers in an ASP.NET MVC application if I need exactly one number per request? According to MSDN, in order to get randomness of sufficient quality, it is necessary to generate multiple numbers using a single System.Random object, created once. Since a new instance of a controller class is created for each request in MVC, I cannot use a private field initialized in the controller's constructor for the Random object. So in what part of the MVC app should I create and store the Random object? Currently I store it in a static field of the controller class and lazily initialize it in the action method that uses it: public class HomeController : Controller { ... private static Random random; ... public ActionResult Download() { ... if (random == null) random = new Random(); ... } } Since the "random" field can be accessed by multiple instances of the controller class, is it possible for its value to become corrupted if two instances attempt to initialize it simultaneously? And one more question: I know that the lifetime of statics is the lifetime of the application, but in case of an MVC app what is it? Is it from IIS startup till IIS shutdown?

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  • Why do some APIs provide mostly interfaces, not classes?

    - by Lord Torgamus
    Some Java APIs provide a large number of interfaces and few classes. For example, the Stellent/Oracle UCM API is composed of roughly 80% interfaces/20% classes, and many of the classes are just exceptions. What is the technical reason for preferring interfaces to classes? Is it just an effort to minimize coupling? To improve encapsulation/information hiding? Something else?

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  • Open source equivelants to VS / web reference proxy classes?

    - by seraphym
    As an ASP.NET developer, I'm used to working with how VS/C# transparently autogens proxy classes for web references (yes, I know, we're spoiled), but now that I'm creating documentation for more than one coding platform I'm trying to discover what the equivelant to that is in any other framework. So is there a similar way to work transparently with web reference proxy classes for say, RoR, PHP, and Python? And if there's nothing integrated, are there tools you recommend to autogen the proxy classes, or do you recommend to roll custom classes?

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  • How to keep track of call statistics? C++

    - by tf.rz
    I'm working on a project that delivers statistics to the user. I created a class called Dog, And it has several functions. Speak, woof, run, fetch, etc. I want to have a function that spits out how many times each function has been called. I'm also interested in the constructor calls and destructor calls as well. I have a header file which defines all the functions, then a separate .cc file that implements them. My question is, is there a way to keep track of how many times each function is called? I have a function called print that will fetch the "statistics" and then output them to standard output. I was considering using static integers as part of the class itself, declaring several integers to keep track of those things. I know the compiler will create a copy of the integer and initialize it to a minimum value, and then I'll increment the integers in the .cc functions. I also thought about having static integers as a global variable in the .cc. Which way is easier? Or is there a better way to do this? Any help is greatly appreciated!

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  • C++ privately contructed class

    - by Nona Urbiz
    How can I call a function and keep my constructor private? If I make the class static, I need to declare an object name which the compiler uses to call the constructor, which it cannot if the constructor is private (also the object would be extraneous). Here is the code I am attempting to use (it is not compilable): I want to keep the constructor private because I will later be doing a lot of checks before adding an object, modifying previous objects when all submitted variables are not unique rather than creating new objects. #include <iostream> #include <fstream> #include <regex> #include <string> #include <list> #include <map> using namespace std; using namespace tr1; class Referral { public: string url; map<string, int> keywords; static bool submit(string url, string keyword, int occurrences) { //if(Referrals.all.size == 0){ // Referral(url, keyword, occurrences); //} } private: list<string> urls; Referral(string url, string keyword, int occurrences) { url = url; keywords[keyword] = occurrences; Referrals.all.push_back(this); } }; struct All { list<Referral> all; }Referrals; int main() { Referral.submit("url", "keyword", 1); }

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