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• What to return as an iterator when there is no container?

  - by DaClown

  I have an inheritance structure of objects with begin() and end() as pure virtual member functions in the base class. From this objects I'm planning to build a composite structure. This inner objects have std::vector member the begin() and end() get their data from. But in a leaf class there is no vector. Now I try to find a return value for begin() and end() in the leaf classes. What would be a good way to do that? The easiest way would be to have a vector member in the leaf classes with no elements in it to fuel begin() and end(), but this just doesn't feel right.

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• exporting non_public type through public API

  - by user329820

  Hi I have written this code in Netbeans but it will show this warning for the name of this method ,would you please help me for what it shows this warning? thanks public Node returnNode(int index) throws IndexOutOfBoundsException { if (index < 0 || index > size) { throw new IndexOutOfBoundsException(); } else { for (int i = 0; i < index; i++) { pointer = pointer.getNext(); } } return pointer; }

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• Simplest one-to-many Map case in Hibernate doesn't work in MySQL

  - by Malvolio

  I think this is pretty much the simplest case for mapping a Map (that is, an associative array) of entities. @Entity @AccessType("field") class Member { @Id protected long id; @OneToMany(cascade = CascadeType.ALL, fetch=FetchType.LAZY) @MapKey(name = "name") private Map<String, Preferences> preferences = new HashMap<String, Preferences>(); } @Entity @AccessType("field") class Preferences { @ManyToOne Member member; @Column String name; @Column String value; } This looks like it should work, and it does, in HSQL. In MySQL, there are two problems: First, it insists that there be a table called Members_Preferences, as if this were a many-to-many relationship. Second, it just doesn't work: since it never populates Members_Preferences, it never retrieves the Preferences. [My theory is, since I only use HSQL in memory-mode, it automatically creates Members_Preferences and never really has to retrieve the preferences map. In any case, either Hibernate has a huge bug in it or I'm doing something wrong.]

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• Seperate compilation in C++

  - by Pat Murray

  Suppose you are creating a class with multiple .cpp files (which each contain the implementation of a member function) and have the class' declaration in a .h file. Also, each .cpp file includes the .h file via the include directive. I was told that if you change the implementation of any of the member functions (.cpp files) that you will have to recompile every .cpp file in order to run the program. That is, if I had 5 member functions (each implemented in a .cpp file) and I changed the implementation of 1 of the .cpp files I would have to compile the 1 .cpp file I changed AND the 4 other .cpp files I didn't change in order to correctly run my program. My question, if the previous statement is true, is why is the statement is true? Any insight on this concept would be helpful.

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• Serializing System.Drawing.Color in .NET

  - by alankdkd

  Hi all, I've used the default .NET serialization for a class with a System.Drawing.Color member. The code is now in use by people, and I need to add an extra member to the class, but still deserialize older versions. So I tried the standard way of doing this: The ISerializable interface, using SerializationInfo methods to get the int and string members. The problem: My class also has a System.Drawing.Color member, but SerializationInfo doesn't provide a "GetColor" method read this data type. I've tried getting it as an int and as a string, and casting it to System.Drawing.Color, but no luck. Does anyone know how to deserialize a System.Drawing.Color from SerializationInfo? Thanx! Alan

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• Nonstatic conversion functions; Casting different types, e.g. DirectX vector to OpenGL vector

  - by Markus

  I am currently working on a game "engine" that needs to move values between a 3D engine, a physics engine and a scripting language. Since I need to apply vectors from the physics engine to 3D objects very often and want to be able to control both the 3D, as well as the physics objects through the scripting system, I need a mechanism to convert a vector of one type (e.g. vector3d<float>) to a vector of the other type (e.g. btVector3). Unfortunately I can make no assumptions on how the classes/structs are laid out, so a simple reinterpret_cast probably won't do. So the question is: Is there some sort of 'static'/non-member casting method to achieve basically this: vector3d<float> operator vector3d<float>(btVector3 vector) { // convert and return } btVector3 operator btVector3(vector3d<float> vector) { // convert and return } Right now this won't compile since casting operators need to be member methods. (error C2801: 'operator foo' must be a non-static member)

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• [c]how to take input for a character pionter without using fget?

  - by ashish yadav

  consider the code include int main() {char* a; scanf("%s",a);//&a and &a[0] give same results-crashes printf("%s",); return 0; } why does this code results in crashing?whereas this code using character array works fine? include int main() {char a[100]; scanf("%s",&a[0]);//works fine printf("%s",a); return 0; } the difference being character array and pointer?but i knew that pointer just points to the first element that is &a[0] should work fine but upper code crashes for all three that is a,&a and &a[0]? the main thing i would to gather is how can i take input of a character pointer if i insist on using scanf only? i apologize if i am not clear. thanks in advance:)

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• Sorting 1000-2000 elements with many cache misses

  - by Soylent Graham

  I have an array of 1000-2000 elements which are pointers to objects. I want to keep my array sorted and obviously I want to do this as quick as possible. They are sorted by a member and not allocated contiguously so assume a cache miss whenever I access the sort-by member. Currently I'm sorting on-demand rather than on-add, but because of the cache misses and [presumably] non-inlining of the member access the inner loop of my quick sort is slow. I'm doing tests and trying things now, (and see what the actual bottleneck is) but can anyone recommend a good alternative to speeding this up? Should I do an insert-sort instead of quicksorting on-demand, or should I try and change my model to make the elements contigious and reduce cache misses? OR, is there a sort algorithm I've not come accross which is good for data that is going to cache miss?

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• Best way to call other class view in iphone?

  - by aman-gupta

  Hi, Generally i call my other class view by creating a pointer of delegate and then call the other class by using its link as below:- First Way :- Mydelegate *ptr = (Mydelegate *)[[UIApplication sharedApplication]delegate]; [self.navigationController pushViewController:ptr.NextClasspointer animated:YES]; Second Way :- Create a pointer of that class which u want to call :-- NextClass *nextptr = [[NextClass alloc]initWithnibName:@"NextClass" bundle:nil]; [self.navigationController pushViewController:nextptr animated:YES]; [nextptr release]; nextptr = nil; These above two methods i generally used but my problem is that which one is best for big project so that my stack problem will be removed I mean memory issue will be solved.And is it necessary to release pointer in first and second case is the way i release is correct or wrong Please help me Thanks in Advance

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• Should every class have its own namespace?

  - by thehouse

  Something that has been troubling me for a while: The current wisdom is that types should be kept in a namespace that only contains functions which are part of the type's non-member interface (see C++ Coding Standards Sutter and Alexandrescu or here) to prevent ADL pulling in unrelated definitions. Does this imply that all classes must have a namespace of their own? If we assume that a class may be augmented in the future by the addition of non-member functions, then it can never be safe to put two types in the same namespace as either one of them may introduce non-member functions that could interfere with the other. The reason I ask is that namespaces are becoming cumbersome for me. I'm writing a header-only library and I find myself using classes names such as project::component::class_name::class_name. Their implementations call helper functions but as these can't be in the same namespace they also have to be fully qualified!

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• The ** idiom in C++ for object construction

  - by bobobobo

  In a lot of C++ API'S (COM-based ones spring to mind) that make something for you, the pointer to the object that is constructed is usually required as a ** pointer (and the function will construct and init it for you) You usually see signatures like: HRESULT createAnObject( int howbig, Object **objectYouWantMeToInitialize ) ; -- but you seldom see the new object being passed as a return value. Besides people wanting to see error codes, what is the reason for this? Is it better to use the ** pattern rather than a returned pointer for simpler operations such as: wchar_t* getUnicode( const char* src ) ; Or would this better be written as: void getUnicode( const char* src, wchar_t** dst ) ; The most important thing I can think of is to remember to free it, and the ** way, for some reason, tends to remind me that I have to deallocate it as well.

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• Access to bytes array of a Bitmap

  - by Deulis

  1- In Windows CE, I have a Bitmap object in C#. 2- I have a C function in an extern dll that expects as parameters the pointer to a bytes array that represents an image in RGB565 format, width and height. This function will draw on this array of bytes. So I need to pass the byte array pointer of the Bitmap object, but I can find a practical way to get this pointer. One way is convert this Bitmap into a bytes array using a memory stream or something else, but it will create a new bytes array, so I will keep in memory both object, the Bitmap and the bytes array, but I don’t want it because the few available memory, that’s why I need to access to the bytes array of the bitmap object, not create a new bytes array. Anyone can help me?

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• Class Members Over Exports

  - by VirusEcks

  When Using DLLs or Code-injecting to be Specific this is an example class only intended for explaining class test { int newint1; char newchararray[512]; void (*newfunction1)( int newarg1 ); int newfunction2( bool newarg1, char newarg2 ) { return newint1; } } mynewclass1; that covers most common elements that's included in classes now when exporting this function to another DLL or application and missed an element of those, either data member or function member, private or public what happens or changed their order ? and if each function is assigned it's value when Code-Injecting like mynewclass1.newfunction1 = (void *)(newexportedfunction); what's the happens in this case, if members of the class are pointers that are assigned after class construction and then missed one member or changed their order ?

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• A brief question about JS or AJAX

  - by Luke

  I have been finding ways around this for a long time but think it's time I addressed it. If I have a page that has a dropdown menu, is there anyway I can select a value which will subsequently load other values further down. Can this be done without a page reload? I will give you an example. Say I was making some tools for an admin panel, but first of all they needed to select a member to work with. They would select the member and then below, the fields about that member would be populated based on what was selected in the first menu. As I have already asked, can this be done without a page reload? Thanks for reading.

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• [c++] does a const reference prolong the life of a temporary or not?

  - by Kyle

  Why is the output to this #include <string> #include <iostream> using namespace std; class Sandbox { public: Sandbox(const string& n) : member(n) {} const string& member; }; int main() { Sandbox sandbox(string("four")); cout << sandbox.member << endl; return 0; } this The answer is: and not The answer is: four ?

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• How do I use SPMemember.ID property to get User or Group

  - by Jason

  I have to write a utility to enumerate and manage the owners of groups within a SharePoint site. I know I can use the Groups property of the SPWeb object to retrieve a collection of groups. And I know I can use the Owner property of the group to get back the owner. My problem is that I do not know what to do next. The SPGroup.Owner property returns a SPMember object. The member object has one property called ID that returns the unique ID (an integer) of the member. What I cannot seem to find information on is how to use that integer value to determine if the member is a User or a Group and how to get back additional details (say the name). Any ideas? Thanks.

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• C++: Question about freeing memory

  - by Martijn Courteaux

  On Learn C++, they wrote this to free memory: int *pnValue = new int; // dynamically allocate an integer *pnValue = 7; // assign 7 to this integer delete pnValue; pnValue = 0; My question is: "Is the last statement needed to free the memory correctly, completly?" I thought that the pointer *pnValue was still on the stack and new doesn't make any sense to the pointer. And if it is on the stack it will be cleaned up when the application leaves the scope (where the pointer is declared in), isn't it?

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• Doctrine2: Filtering by ManToMany Association

  - by Shroder

  I want to retrieve a collection of objects based on what they are associated to. For example, by a category. This would be a Many to Many relationship. I've been able to achieve that with MEMBER OF, however I need to pass in an array of IDs, opposed to one at a time. I see there is an "IN ()", but it seems to require a subquery, which I would like to avoid. MEMBER OF example: SELECT o FROM Entity\Object1 o WHERE 'CATEGORY_CODE' MEMBER OF o.categories (Edit) This is what I would like to do, but perhaps I'm misunderstanding how entities work in DQL: SELECT o FROM Entity\Object1 o WHERE o.categories.Id IN (id, id, id)

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• How to Change Type of a VARIANT

  - by nimo

  Hi, I'm having a VARIANT with its type set to VT_R8. Subsequently I need to change its type to VT_BSTR. I would like know whether there is a way of resetting a VARIANT status. Thus, I noticed that every time I set value to the VARIANT (in my case, its double) , VARIANT itself set its bstrVal member to a bad pointer, even though I set bstrVal member to NULL at the initialization of VARIANT. Why such thing is happening ? Is it safe to use a VARIANT as structure where both dbVal and bstrVal member are set ? Please clarify, thank you.

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• Is void *p = 0L valid?

  - by Artefacto

  In this answer, sassman initializes a pointer with: zend_class_entry* ce = 0L; My question is – is this valid? I would say it isn't, to initialize the variable with a null pointer either an unadorned (and possibly casted to void *) 0 constant, or some macro that evaluates to that such as NULL should be used. However, I can't find definitive language in the standard that supports this interpretation. All it says is: An integer constant expression with the value 0, or such an expression cast to type void *, is called a null pointer constant.

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• Determine an object's class returned by a factory method (Error: function does not take 1 arguments

  - by tzippy

  I have a factorymethod that either returns an object of baseclass or one that is of derivedclass (a derived class of baseclass). The derived class has a method virtual void foo(int x) that takes one argument. baseclass however has virtual void foo() without an argument. In my code, a factory method returns a pointer of type bar that definetly points to an object of class derivedclass. However since this is only known at runtime I get a compiler error saying that foo() does not take an argument. Can I cast this pointer to a pointer of type derivedclass? std::auto_ptr<baseclass> bar = classfactory::CreateBar(); //returns object of class derivedclass bar->foo(5); class baseclass { public: virtual void foo(); } class derivedclass : public baseclass { public: virtual void foo(int x); }

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• give apache permission to write files to folder

  - by user1683645

  I'm trying to give www-data which is the name of the apache on my ubuntu permission to write files to folders. The entire website is in /media/root/data/ and I've got member folders containing the user specific images. apache tmp folder is set to: /media/root/data/tmp and the permission is set for www-data to read and write to it. About member folders that contain images. First off I tried giving www-data the rw permission and upload an image, but it did not work. Everything else in the site works except uploading files. How do I automaticly give apache rw permission to new member folders? And why cant I write to it?

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• conversions in C++

  - by lego69

  I have this snippet of the code: header class A { private: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); ~A(); void foo() const; friend A& operator=(A& i, const A& member); }; operator= A& operator=(A& i, const A& member){ i(member.player); return i; } and I have row in my code: i = *pa1; A *pa1 = new A(a2); at the beginning i was int how can I fix it, thanks in advance I have an error must be non-static function

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• If item not in the lst in scheme

  - by ms. sakura

  I'm working on context-free grammars, and I have a function that returns the (terminal values of grammar) for example: i have non-terminal function that results in (A B) , from calling say ((A cat) (B happy np) (A B sad)) so technically A and B are non terminals of the grammar. Now I want to be able to get the terminals (cat happy np sad) (define terminals (lambda (lsts) (cond ((null? lsts) lsts) ((not(member? (car(car lsts)) (n-terminals lsts))) (cons (car(car lsts)) (terminals (car (cdr lsts))))) (else (terminals (cdr lsts)))))) PS: functionality of n-terminals is described above. member? is a boolean function that returns true if an item is a member of the list, false otherwise. My function returns an empty lst. What am I missing here?

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• in c++ what is bettr to delete poiner or set it with new value?

  - by user63898

  Hi simple question in c++ , say i have a loop and i have function that returns pointer to item so i have to define inner loop pointer so my question is what to do with the pointer inside the loop , delete it ? or to set it with new value is good for example: for(int i =0;i<count();i++) { ptrTmp* ptr = getItemPtr(); // do somthing with the ptr ... // what to do here ? to delete the poinetr or not? delete ptr; // ?? }

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