dynamic-allocation

问题 As I make the transition from C# to C++ I get a lot of recommendations to use value semantics where possible. It's pretty much guaranteed that if I post a question with a pointer anywhere someone will come along and suggest that it should be a value instead. I'm starting to see the light and I have found a lot of places in my code where I could replace dynamic allocation and pointers with stack allocated variables (and usually references). So I think I have a grasp on using stack allocated

问题 I have to write a subroutine in Fortran 77(i'm using Intel Fortran), which reads the measured values from a text file and stores them in a matrix. Since the number of measured values is always variable, I must dynamically allocate the matrix. I know that the dynamic allocation is only possible from Fortran 90, but at that time people had the same problems, so it is also possible. How would you proceed? I do not want to reserve too much space for the matrix because the method is impractical

问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 5 years ago . After years of programming, I havent had a situation where reasonable malloc or new would fail (maybe because my mallocs are trully reasonable), though I always check for it. In my case, apps should gracefully (i hope) close with an appropriate log entry. What would you do in

问题 As per Why malloc+memset is slower than calloc? malloc + memset is slower than calloc under certain conditions. Why wasn't calloc written in such a way that it can take an extra value argument ( like memset ) to override default assignment by zero? What would have been the effect of that if it were done? 回答1: These calloc or memset initializations operate on a byte level, so even memset with a value different from 0 is not that usefull. At least I don't remember having it used with different

问题 I'm starting out with structures, and I'm having problems dynamically allocating my structure array. I'm doing what I see in my book and on the internet, but I can't get it right. Here's both full error messages: C2512: 'Record' : no appropriate default constructor available IntelliSense: no default constructor exists for class "Record" #include <iostream> #include <string> using namespace std; const int NG = 4; // number of scores struct Record { string name; // student name int scores[NG];

问题 I wrote a code for managing a library; the compilation is done but during the simulation I obtained an Allocation error (case2) and I don't know why. The first case works correctly but if I entered more than one name in the first case, the second case doesn't work. What did I do wrong? I hope I was clear enough. typedef struct { char name[80]; char **books; int books_num; } Subscription; int main() { // Variables declaration: int option = 0, subs_num = 0, i = 0, books_num = 0; Subscription

问题 The argument of my fortran 95 subroutine is an assumed shape array with intent inout: the_subroutine(my_argument) real, dimension(:,:), intent(inout) :: my_argument (...) In the main program, I have an allocatable array. I allocate it and also rename indexes . Then I call the subroutine and pass that (correctly allocated) array to the subroutine: allocate(the_array( 5:1005 , 5:1005 )) call the_subroutine(my_argument=the_array) The subroutine does certain calculations and fills the array with

问题 My program starts with a dynamically allocated (DA) array. It then prompts the user to enter in a size. If the size entered is within a certain threshold, a new DA array is created, the contents of the old is copied into the new, and the new array is then displayed. I am having trouble copying contents from one dynamically DA array into the other dynamically allocated array. Through each step of the reallocation process I have "print tests" that display the array after each process. I test

问题 The intent of this question is to provide a reference about how to correctly allocate multi-dimensional arrays dynamically in C. This is a topic often misunderstood and poorly explained even in some C programming books. Therefore even seasoned C programmers struggle to get it right. I have been taught from my programming teacher/book/tutorial that the correct way to dynamically allocate a multi-dimensional array is by using pointer-to-pointers. However, several high rep users on SO now tell

问题 I am working on implementing a vector class but cannot figure out how to write a function to copy one vector into another. template <class T> class Vec { public: //TYPEDEFS typedef T* iterator; typedef const T* const_iterator; typedef unsigned int size_type; //CONSTRUCTOS, ASSIGNMENT OPERATOR, & DESTRUCTOR Vec() {this->create(); } Vec(size_type n, const T& t = T()) { this->create(n, t); } Vec(const Vec& v) { copy(v); } Vec& operator=(const Vec& v); ~Vec() { delete [] m_data; } //MEMBER