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

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• How to kill the process in different group but not one-by-one?

  - by skydoor

  Can we just put all the processes in one group and kill that group? Is there any other way to do this?

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• Is there any thing hashmap can do but map cannot?

  - by skydoor

  Hi, I only know that the difference between hashmap and map is that hashmap is implemented with hash function but map is implemented with tree. Could any body add anything more? Based on this, is there any thing hashmap can do but map cannot?

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• question about STL thread-safe and STL debugging

  - by skydoor

  I have two questions about STL 1) why STL is not thread-safe? Is there any structure that is thread-safe? 2) How to debug STL using GDB? In GDB, how can I print a vector?

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• operator new for array of class without default constructor......

  - by skydoor

  For a class without default constructor, operator new and placement new can be used to declare an array of such class. When I read the code in More Effective C++, I found the code as below(I modified some part)..... My question is, why [] after the operator new is needed? I test it without it, it still works. Can any body explain that? class A { public: int i; A(int i):i(i) {} }; int main() { void *rawMemory = operator new[] (10 * sizeof(A)); // Why [] needed here? A *p = static_cast<A*>(rawMemory); for(int i = 0 ; i < 10 ; i++ ) { new(&p[i])A(i); } for(int i = 0 ; i < 10 ; i++ ) { cout<<p[i].i<<endl; } for(int i = 0 ; i < 10 ; i++ ) { p[i].~A(); } return 0; }

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• Can destructors be declared as pure virtual? [closed]

  - by skydoor

  Possible Duplicate: Why do we need a pure virtual destructor in C++? I know that the destructor can be virtual, how about pure virtual? If yes, what's the usage? If not, what's the error, compile error or runtime error?

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• question about sorting

  - by skydoor

  Bubble sort is O(n) at best, O(n^2) at worst, and its memory usage is O(1) . Merge sort is always O(n log n), but its memory usage is O(n). Which algorithm we would use to implement a function that takes an array of integers and returns the max integer in the collection, assuming that the length of the array is less than 1000. What if the array length is greater than 1000?

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• What's pthread in Boost?

  - by skydoor

  I found there are also a pthread in Boost library, is it the same thing as the posix pthread?

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• Why friend overloaded operator is preferred to conversion operator in this case

  - by skydoor

  Hi I have a code like this, I think both the friend overloaded operator and conversion operator have the similar function. However, why does the friend overloaded operator is called in this case? What's the rules? Thanks so much! class A{ double i; public: A(int i):i(i) {} operator double () const { cout<<"conversion operator"<<endl;return i;} // a conversion operator friend bool operator>(int i, A a); // a friend funcion of operator > }; bool operator>(int i, A a ){ cout<<"Friend"<<endl; return i>a.i; } int main() { A aa(1); if (0 > aa){ return 1; } }

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• what happened if an exception is not captured?

  - by skydoor

  I am not asking an unexpected exception, but an exception that is not captured. Crashed? Or terminated?

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• Factory, Abstract Factory and Factory Method

  - by skydoor

  Hi, I am really confused about these three terms. My understanding is that: in the Factory pattern, there is no concrete factory. The factory builds the new objects according to the parameters. in Abstract Factory pattern, there are multiple concrete factories. The client has to create different concrete factories explicitly. Is that right? What are the other differences? Furthermore, what is the Factory Method pattern? Is it same as the Factory pattern?

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• why weak_ptr can break cyclic reference?

  - by skydoor

  I learnt a lot about weak_ptr working with share_ptr to break cyclic reference. How does it work? How to use that? Can any body give me an example? I am totally lost here. One more question, what's a strong pointer?

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• How to catch the exception in initialization list?

  - by skydoor

  Hi I have a question about how to catch the exception in the initialization list. For example, we have a class Foo derived from Bar class Foo { public: Foo(int i) {throw 0; } } class Bar : public Foo{ public: Bar() : Foo(1) {} }

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• What are shared by multi threads in the same process?

  - by skydoor

  I found that each thread still has its own registers. Also has its own stack, but other threads can read and write the stack memory. My questions, what are shared by the multi threads in the same process? What I can imagine is 1) address space of the process; 2) stack, register; 3) variables Can any body elaborate it and add more?

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• The problem of return reference to local variable

  - by skydoor

  I happened to find this code return 5. It's OK to write it this way or should definitely be avoid? int& f() { int i = 5; return i; } int main(){ cout<<f()<<endl; }

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• why pointer to pointer is needed to allocate memory in function

  - by skydoor

  Hi I have a segmentation fault in the code below, but after I changed it to pointer to pointer, it is fine. Could anybody give me any reason? void memory(int * p, int size) { try{ p = (int *) malloc(size*sizeof(int)); } catch( exception& e) { cout<<e.what()<<endl; } } it does not work in the main function as blow int *p = 0; memory(p, 10); for(int i = 0 ; i < 10; i++) p[i] = i; however, it works like this . void memory(int ** p, int size) { `//pointer to pointer` try{ *p = (int *) malloc(size*sizeof(int)); } catch( exception& e) { cout<<e.what()<<endl; } } int main() { int *p = 0; memory(&p, 10); //get the address of the pointer for(int i = 0 ; i < 10; i++) p[i] = i; for(int i = 0 ; i < 10; i++) cout<<*(p+i)<<" "; return 0; }

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• Some questions about Vector in STL

  - by skydoor

  I have some questions about vector in STL to clarify..... Where are the objects in vector allocated? heap? does vector have boundary check? If the index out of the boundary, what error will happen? Why array is faster than vector? Is there any case in which vector is not applicable but array is a must?

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• how is push_back implemented in STL vector?

  - by skydoor

  I was asked this question in an interview. The points I answered are like this 1) an index pointing to the current position; 2) resize if neccessary. Can anybody elaborate more?

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• Any drawbacks with all member functions declared virtual?

  - by skydoor

  If I am developing a class and don't know how it will be used, are there any drawbacks to declaring all the member functions virtual? Is this a good or bad design?

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• one question about iostream cout in C++

  - by skydoor

  Hi In such code, what it is called, \\n like this? cout<<"Hello\\n \'world\'!"; What's the basic rule about such characters?

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• Why malloc memory in a function and free it outside is a bad idea?

  - by skydoor

  if this is a bad idea, how to allocate memory in the function?

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• What the difference between deadlock avoidance and deadlock prevention?

  - by skydoor

  I met two terms and are they the same thing or different thing?

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• volatile vs. mutable in C++

  - by skydoor

  Hi I have a question about the difference between volatile and mutable. I noticed that both of the two means that it could be changed. What else? Are they the same thing? What's the difference? Where are they applicable? Why the two ideas are proposed? How to use them in different way? Thanks a lot.

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• How default assignment operator works in struct?

  - by skydoor

  Suppose I have a structure in C++ containing a name and a number, e.g. struct person { char name[20]; int ssn; }; Suppose I declare two person variables: person a; person b; where a.name = "George", a.ssn = 1, and b.name = "Fred" and b.ssn = 2. Suppose later in the code a = b; printf("%s %d\n",a.name, a.ssn);

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• What's wrong with these pointer initialization

  - by skydoor

  char * a=0; int * b=0; cout<<a<<a+1; cout<<b<<b+1; what's wrong with it

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• How to make this code compile?

  - by skydoor

  // File: foo.c static int var; void foo() { var++; } // end of file foo.c // File bar.c: static int var; void bar() { var++; } // end of file bar.c // file main.c static int var; void main() { foo(); bar(); printf("%d", var); } // end of file main.c Question: Will the above program compile ? If so what will be the result ? I tested the code and found it couldn't be compiled. I try to use extern in main.c to use the function foo() and bar() but it still couldn't be compiled.

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