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• What could possibly cause this error(when declaring an object inside a class) ? //noobie question

  - by M4design

  I'm battling with this assignment :) I've got two classes: Ocean and Grid. When I declare an object of the Grid inside the Ocean: unsigned int sharkCount; Grid grid; The compiler/complainer says: error C2146: syntax error : missing ';' before identifier 'grid' Can you possibly predict what produces this error with the limited info' I provided? It seems that as if the Ocean doesn't like the Grid class. Could this be because of the poor implementation of the grid class. BTW the Grid has a default constructor. Yet the error happens in compiling time!. Thanks. EDIT: They're each in separate header file, and I've included the Grid.h in the Ocean.h.

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• Undefined behaviour with non-virtual destructors - is it a real-world issue?

  - by Roddy

  Consider the following code: class A { public: A() {} ~A() {} }; class B: public A { B() {} ~B() {} }; A* b = new B; delete b; // undefined behaviour My understanding is that the C++ standard says that deleting b is undefined behaviour - ie, anything could happen. But, in the real world, my experience is that ~A() is always invoked, and the memory is correctly freed. if B introduces any class members with their own destructors, they won't get invoked, but I'm only interested in the simple kind of case above, where inheritance is used maybe to fix a bug in one class method for which source code is unavailable. Obviously this isn't going to be what you want in non-trivial cases, but it is at least consistent. Are you aware of any C++ implementation where the above does NOT happen, for the code shown?

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• Simultaneous private and public inheritance in C++

  - by gspr

  Suppose a class Y publicly inherits a class X. Is it possible for a class Z to privately inherit Y while publicly inheriting X? To make this clearer, suppose X defines public methods x1 and x2. Y inherits X, overrides x1 and provides a method y. Does C++ allow for a third class Z to subclass Y in such a way that Y's implementation of x1 and y are privately available to it, while the outside world only sees it inheriting X publicly, i.e. having only a single public method x2?

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• Does "Value Restriction" practically mean that there is no higher order functional programming?

  - by Sadache

  Does "Value Restriction" practically mean that there is no higher order functional programming? I have a problem that each time I try to do a bit of HOP I get caught by a VR error. Example: let simple (s:string)= fun rq->1 let oops= simple "" type 'a SimpleType= F of (int ->'a-> 'a) let get a = F(fun req -> id) let oops2= get "" and I would like to know whether it is a problem of a prticular implementation of VR or it is a general problem that has no solution in a mutable type-infered language that doesn't include mutation in the type system.

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• How to add response headers based on Content-type; getting Content-type before the response is commi

  - by Bozho

  I want to set the Expires header for all image/* and text/css. I'm doing this in a Filter. However: before calling chain.doFilter(..) the Content-type is not yet "realized" after calling chain.doFilter(..) the Content-type is set, but so is content-length, which forbids adding new headers (at least in Tomcat implementation) I can use the extensions of the requested resource, but since some of the css files are generated by richfaces by taking them from inside jar-files, the name of the file isn't x.css, but is /xx/yy/zz.xcss/DATB/.... So, is there a way to get the Content-type before the response is committed.

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• Purpose of IF, ELSE, FOR macros ?

  - by psihodelia

  I have a source code of a library which has a lot of strange IF, ELSE, FOR, etc. macros for all common C-keywords instead of using just usual if,else,for,while keywords. These macros are defined like this: #define IF( a) if( increment_if(), a) where increment_if() function is defined so: static __inline void increment_if( void) { // If the "IF" operator comes just after an "ELSE", its counter // must not be incremented. ... //implementation } I don't really understand, what is the purpose of such macros? This library is for a real-time application and I suppose that using such macros must slow-down an application.

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• Is there a way to intersect/diff a std::map and a std::set?

  - by Jack

  I'm wondering if there a way to intersect or make the differences between two structures defined as std::set<MyData*> and std::map<MyData*, MyValue> with standard algorithms (like std::set_intersect) The problem is that I need to compute the difference between the set and the keyset of the map but I would like to avoid reallocating it (since it's something that is done many times per second with large data structures). Is there a way to obtain a "key view" of the std::map? After all what I'm looking is to consider just the keys when doing the set operation so from an implementation point it should be possible but I haven't been able to find anything.

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• Qt and finding partial matches in a QList

  - by ExpatEgghead

  I have a struct viz: struct NameKey { std::string fullName; std::string probeName; std::string format; std::string source; } which are held in a QList: QList<NameKey> keyList; what I need to do is find an occurence in keyList of a partial match where the search is for a NameKey that only has two members filled. All the keyList entries are full NameKey's. My current implementation is , well, boring in the extreme with too many if's and conditions. So, If I have a DataKey with a fullName and a format I need to find all the occurences in keyList which match. Any useful Qt/boost things available?

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• how to create resources without VS C++ 2008 creating MFC files

  - by numerical25

  I am creating a WIN32 application and I want most of all my application events to be made through the message queue. But everytime I create a dialog box or any resource like that. The IDE auto generates code that I don't necessarily need. I believe it's MFC code not sure. here it is. // dlgChangeDevice.cpp : implementation file // #include "stdafx.h" #include "ZFXD3D.h" #include "dlgChangeDevice.h" // dlgChangeDevice dialog IMPLEMENT_DYNAMIC(dlgChangeDevice, CDialog) dlgChangeDevice::dlgChangeDevice(CWnd* pParent /*=NULL*/) : CDialog(dlgChangeDevice::IDD, pParent) { } dlgChangeDevice::~dlgChangeDevice() { } void dlgChangeDevice::DoDataExchange(CDataExchange* pDX) { CDialog::DoDataExchange(pDX); } BEGIN_MESSAGE_MAP(dlgChangeDevice, CDialog) ON_CBN_SELCHANGE(IDC_COMBO5, &dlgChangeDevice::OnCbnSelchangeCombo5) END_MESSAGE_MAP() // dlgChangeDevice message handlers void dlgChangeDevice::OnCbnSelchangeCombo5() { // TODO: Add your control notification handler code here } Not sure what it is but I don't need it. I want to retrieve all my code through the dialog message queue. So what should I do ?? Just disregard it and delete it. Will a hurt anything by doing so ??

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• Object initialization sequence in Objective-C

  - by Alex

  Hello everyone. The Cocoa framework has a convention to always call self = [super init] in the init method of an inherited class, because [super init] may return a new instance. What will happen if I do this? @interface MyClass : NSObject /* or any other class */ { int ivar_; } @end @implementation MyClass - (id)init { ivar_ = 12345; if ((self = [super init])) { NSLog(@"ivar_'s value is %d", ivar_); } return self; } @end In the case when [super init] returns a new instance, what will I see in the console? ivar_'s value is 0? I can't think of a way to check this myself, because I don't know which class may return a new instance from its init method. Also, can't seem to find explicit clarification for this scenario in the docs. Could anyone help me out? Thanks!

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• Code generation tool, to create C# adapter classes for unit testing?

  - by RyBolt

  I know I wouldn't need this with Typemock, however, with something like MoQ , I need to use the adapter pattern to enable the creation of mocks via interfaces for code I don't control. For example, TcpClient is a .NET class, so I use adapter pattern to enable mocking of this object, b/c I need an interface of that class. I then produce interface ITcpClient, that can then be implemented via a TcpClientAdapter class, which is just plain vanilla adapter pattern implementation. I am looking for a tool to do this automatically (creation of interface and adapter), I would think there is one out there somewhere? (or is everyone just hand coding these)

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• Get the Time Interval without ITimer

  - by ronag

  In my application I am hosting a flash activex control, based on the following implementation. However I need to know in what fps the control is running in when it is "ticked". The only way I know of to do this is to implement ITimerService and ITimer to get the vtimeInterval argument from ITimer::Advise. However, I do not want to control my own custom ITimer, instead I want the control to be timed using the default timer (basically sends WM_USER + 1 messages to the message queue at proper intervals) which is used when a custom ITimer is not provided. How can I read the vTimeInterval while still using the default timer?

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• DDD Infrastructure services

  - by Zygimantas

  Hello, I am learning DDD and I am a little bit lost in Infrastructure layer: As I understand, "all good DDD applications" should have 4 layers: Presentation, Application, Domain and Infrastructure. Database should be accessed using Repositories. Repository interfaces should be in Domain layer and repository implementation - in Infrastructure (reference http://stackoverflow.com/questions/693221/ddd-where-to-keep-domain-interfaces-the-infrastructure). Application, Domain and Infrastructure layer should/may have services (reference www.lostechies.com/blogs/jimmy_bogard/archive/2008/08/21/services-in-domain-driven-design.aspx), in example EmailService in Infrastructure layer which sends Email messages. BUT, inside Infrastructure layer we have repository implementations, which are used to access database. So, in this case, repositories are database services? What is the difference between Infrastructure service and repository? Thanks in advance!

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• what is serialization and how it works

  - by Rozer

  I know the serialization process but have't implemented it. In my application i have seen there are various classes that has been implemented serilizable interface. consider following class public class DBAccessRequest implements Serializable { private ActiveRequest request = null; private Connection connection = null; private static Log log = LogFactory.getLog(DBAccessRequest.class); public DBAccessRequest(ActiveRequest request,Connection connection) { this.request = request; this.connection = connection; } /** * @return Returns the DB Connection object. */ public Connection getConnection() { return connection; } /** * @return Returns the active request object for the db connection. */ public ActiveRequest getRequest() { return request; } } just setting request and connection in constructor and having getter setter for them. so what is the use of serilizable implementation over here...

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• C++ boost thread id and Singleton

  - by aaa

  hi. Sorry to flood so many questions this week. I assume thread index returned by thread.get_id is implementation specific. In case of the pthreads, is index reused? IE, if thread 0 runs and joins, is thread launched afterwords going to have a different ID? the reason I ask this is a need to implement Singleton pattern with a twist: each thread gets its own instance. I know it sounds very crazy, but threads control hardware (cuda) which does not permit device memory sharing. What is a good way to implement such pattern?

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• has_many relation doesn't seems right or logical in business perceptive, needed some thing like belo

  - by Vijendra

  My situation is like this. Company has many users and users may belongs to many companies. And current implementation is something like below. class Company has_many :employments has_many :users, :through = :employments end class Employment belongs_to :company belongs_to :user end class User has_many :employments has_many :companies, :through = :employments #This doesn't looks correct end It works, but "user has many companies" doesn't looks logically meaningful. It must be some thing like belongs_to_many companies. Do I need to use has_and_belongs_to_many? Can some one please suggest the right way for representing these relationships?

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• WCF Client - Best Practise

  - by user1663907

  I just wanted to hear your Opinion about a WCF Client implementation. I have an Server that provides several services like SecurityManager. This service is defined in the Interface ISecurityManager and implemented in the Class SecurityManager. So far everything is fine. On the Client side I want to implement the services calls via a seperated Class. My question is whether I do this also in an SecurityManager Class which implements the same ISecurityManager Interface? What is here the best practise? Thanks.

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• WebView not responding when called from a method

  - by AragornSG

  I have an app with tabbar and webview. I'm trying to make the app come back to default url each time user taps the bar. Right now I'm intercepting taps and launching a method, however it's not affecting my webview. The same syntax for calling webview from awakeFromNib works, so I don't have a clue what's up. I suspect it's something to do with how I call the method, but I don't know what. Here is the code: #import "SecondViewController.h" @implementation SecondViewController - (void)awakeFromNib { NSString *loadURL = [NSString stringWithFormat:@"http://pageurl"]; // [secondView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:loadURL]]]; SecondViewController *ptr = [[SecondViewController alloc] init]; [ptr goToPage]; } - (void) goToPage { NSLog(@"go to page"); NSString *newURL = [NSString stringWithFormat:@"http://pageurl"]; [secondView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:newURL]]]; } Thanks fot your help!

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• an error "variable of field declared void"

  - by lego69

  I have this code: header - test.h Inside header I have some class Z and definitions of two functions test and test2 I call function test2 from test void test2(Z z, Z const *za); this is implementation of the function: void test2(Z z, Z const *za){ int i = z; //this row works cout << i << endl; } I call it from test: test2(z1, za1); // za1 is pinter to object and z1 is some object but in my header I receive an 3 errors: Multiple markers at this line - initializer expression list treated as compound expression - `A' was not declared in this scope - variable or field `quiz2' declared void can somebody please explain why? thanks in advance

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• Why exactly is calling the destructor for the second time undefined behavior in C++?

  - by sharptooth

  As mentioned in this answer simply calling the destructor for the second time is already undefined behavior 12.4/14(3.8). For example: class Class { public: ~Class() {} }; // somewhere in code: { Class* object = new Class(); object->~Class(); delete object; // UB because at this point the destructor call is attempted again } In this example the class is designed in such a way that the destructor could be called multiple times - no things like double-deletion can happen. The memory is still allocated at the point where delete is called - the first destructor call doesn't call the ::operator delete() to release memory. For example, in Visual C++ 9 the above code looks working. Even C++ definition of UB doesn't directly prohibit things qualified as UB from working. So for the code above to break some implementation and/or platform specifics are required. Why exactly would the above code break and under what conditions?

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• Objective-C property getter

  - by Daniel

  What is technically wrong with the following: @property(nonatomic, assign) NSUInteger timestamp; @property(nonatomic, readonly, getter = timestamp) NSUInteger startTime; @property(nonatomic, assign) NSUInteger endTime; I am sure I can find a better way to organise this, but this is what I ended up with at one point in my project and I noticed that accessing the startTime property always returned 0, even when the timestamp property was set to a correct timestamp. It seems having set the getter of startTime to an existing property (timestamp), it is not forwarding the value of timestamp when I do: event.startTime => 0 event.timestamp => 1340920893 All these are timestamps by the way. Just a reminder, I know the above should have happened in my project but I don't understand why accessing startTime doesn't forward onto timestamp property. UPDATE In my implementation I am synthesising all of these properties: @synthesize timestamp, endTime, startTime; Please check an example object to use that demonstrates this at my gist on GitHub: https://gist.github.com/3013951

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• Can I add a custom method to Core Data-generated classes?

  - by Andy

  I've got a couple of Core Data-generated class files that I'd like to add custom methods to. I don't need to add any instance variables. How can I do this? I tried adding a category of methods: // ContactMethods.h (my category on Core Data-generated "Contact" class) #import "Contact.h" @interface Contact (ContactMethods) -(NSString*)displayName; @end ... // ContactMethods.m #import "ContactMethods.h" @implementation Contact (ContactMethods) -(NSString*)displayName { return @"Some Name"; // this is test code } @end This doesn't work, though. I get a compiler message that "-NSManagedObject may not respond to 'displayName' " and sure enough, when I run the app, I don't get "Some Name" where I should be seeing it.

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• How to call a function from a shared library?

  - by Frank

  What is the easiest and safest way to call a function from a shared library / dll? I am mostly interested in doing this on linux, but it would be better if there were a platform-independent way. Could someone provide example code to show how to make the following work, where the user has compiled his own version of foo into a shared library? // function prototype, implementation loaded at runtime: std::string foo(const std::string); int main(int argc, char** argv) { LoadLibrary(argv[1]); // loads library implementing foo std::cout << "Result: " << foo("test"); return 0; } BTW, I know how to compile the shared lib (foo.so), I just need to know an easy way to load it at runtime.

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• Comparing Design Patterns

  - by Lijo

  Hi, I am learning design patterns using C#. One of the challenges that I am facing is that they look similar. Could you please help me to distinguish them – basically when to use them? - Why not the other? Bridge and Strategy State and Strategy Façade and Strategy Composite and Strategy I understand that there are lots of resources available in the web. However they does not treat this special question. [Note: I am looking for implementation examples and rationale behind the selection; not mere explanations] It would be great if you are taking examples from any of the following 1) E-Commerce 2) Payroll system 3) Banking 4) Retailing Thanks for your understanding.. Thanks Lijo

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• Better to extend a class or modify it directly?

  - by primehunter326

  Hi, So I'm working on creating a visualization for a data structure in Java. I already have the implementation of the data structure (Binary Search Tree) to start with, but I need to add some additional functionality to the included node class. As far as conventions and best practices are concerned, should I create a subclass of the node with this added functionality or should I just modify what I have and document it there? My question is similar to what's asked here but that's a little over my head. I know it probably doesn't matter much for what I'm doing, so I'm asking this more as a general thing.

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