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Search found 66 results on 3 pages for 'skydoor'.

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• What to do if a failed destructor can't throw an exception

  - by skydoor

  Hi, I noticed that you can't throw an exception in a destructor. So my question is what should I do if destructor fails. Another question is, under what situation a destructor might fail? Thanks so much

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• Is there any c++ class that can't be used in STL?

  - by skydoor

  Just come up with this question. Any hint?

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• how does sizeof work with array in C++

  - by skydoor

  Hi, I was told the array name is a pointer char a[] = "a" but when sizeof(a) = 2 why not it is a size of pointer here? however when I define it like this char* a ="a"; we get sizeof(a) =4; Well, I think I need more information about how does sizeof work with the array names.... Can anyone elaborate that?

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• combination and permutation in C++

  - by skydoor

  What's the most widely used existing library in C++ to give all the combination and permutation of k elements out of n elements? I am not asking the algorithm but the existing library or methods. Thanks.

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• What's the outcome if I use free with new or delete with malloc?

  - by skydoor

  It is a compiler error or runtime error? The code below can be compiled! class Base{ void g(); void h(); }; int main() { Base* p = new Base(); free(p); return 0; } However it can't be compiled with a virtual function if I declare the class Base like this class Base{ virtual void g(); void h(); }; The code below can be compiled all the time, no matter the function is virtual or not. class Base{ void g(); void h(); }; int main() { Base* p = (Base*)malloc(sizeof(Base)); delete p; return 0; }

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• Should I pointer-cast from a private derived class to its base class?

  - by skydoor

  I found this from C++FAQ Generally, No. From a member function or friend of a privately derived class, the relationship to the base class is known, and the upward conversion from PrivatelyDer* to Base* (or PrivatelyDer& to Base&) is safe; no cast is needed or recommended. However users of PrivatelyDer should avoid this unsafe conversion, since it is based on a private decision of PrivatelyDer, and is subject to change without notice. How to understand the above words? I don't think the explanation is correct or accurate. I have a code like this class A{ }; class B: private A{ }; int main(){ B *b = new B(); A *a = new A(); a = b; //wrong a = (A*)b; //right }

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• Does dynamic biding only happen with object on heap in C++?

  - by skydoor

  Will dynamic binding happen with the object on stack? For example f() is a virtual function in both Base and Derived int main(){ Derived d1; Based *b= new Derived(); d1.f(); b->f(); }

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• strcat implementation

  - by skydoor

  I tried to implement the strcat by myself, and I found the strcat implementation from Wiki like this......but when I use it, there is segmentation fault. What's from with the code below? char * strcat(char *dest, const char *src) { size_t i,j; for (i = 0; dest[i] != '\0'; i++) ; for (j = 0; src[j] != '\0'; j++) dest[i+j] = src[j]; dest[i+j] = '\0'; return dest; }

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• When is "this" pointer initialized in C++?

  - by skydoor

  Hi I have a question about this pointer, when an object is constructed, when it is initialized? Which means, when can I use it? The virtual table is constructed in the constructor, is the same with this pointer? For example, I have a code like this. The output is 8. Does it mean that before the constructor is entered, this pointer is already initialized? class A{ public: A() { cout<<sizeof(*this);} int i; int *p; }; int main() { A a; } If it is true, what else would happen before the constructor is entered? If it is not true, when is the this pointer initialized?

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• Can I use vector in a map in STL?

  - by skydoor

  Can I declare a map like this map<string, vector<string>> mymap; I thought it is applicable. However, it shows not. I tried map<string, vector<string>*> mymap; and then it is OK What's the rule of this?

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• Under what situation the static/global variables make program crash before main() in C++?

  - by skydoor

  If the program crashed before main(), the static/global variables are the reasons. I have two questions about this 1) Is this the only reason, what other reasons might make program crash before main()? 2) For static/global variables, how could they make the program crash? During the initialization? How are these variables initialized?

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• Can we overload a function based on only whether a parameter is a value or a reference?

  - by skydoor

  I got the answer NO! Because passing by value and passing by reference looks identical to the caller. However, the code below compiles right class A { public: void f(int i) {} void f(int& i) {} }; But when I try to use it, there is compile error. int main () { A a; int i = 9; int& j = i; a.f(1); a.f(i); a.f(j); return 0; } Why does not the compiler disable it even without knowing it is going to be used?

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• What issue is related with function that return a reference C++

  - by skydoor

  I only know that a function that return a non-const reference is a lvalue, you can assign a value to the function int& f() { return ***} f()=1; What else?

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• When virtual destructor is not needed even there is a virtual function, Why ?

  - by skydoor

  It says that if there is a virtual function, it is a good practice to have a virtual destructor. However, if the object is created on the stack but not on heap, do we still need to do that? Regards,

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• Why can't initialize the static member in a class in the body or in the header file?

  - by skydoor

  Could any body offer me any reason about that? If we do it like that, what's the outcome? Compile error?

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• how to print 0.123 as .123 without 0 in C++?

  - by skydoor

  I would like to print 0.123 as .123, how to do that in C++? I only deal with 0.* as .*

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