pointers

问题 I'm trying to learn the benefits and shortcomings of different ways to get input from the console. I'm confused with scanf . Why do I need to use use &favNumber instead of favNumber ? I understand that &favNumber is the address location of favNumber , but why is it done this way? I feel like there's a type mismatch here where favNumber is an int and I'm telling scanf that it's a pointer to an int. I thought I wrapped my head around pointers but this is confusing me a bit. Any help would be

问题 I'm trying to learn the benefits and shortcomings of different ways to get input from the console. I'm confused with scanf . Why do I need to use use &favNumber instead of favNumber ? I understand that &favNumber is the address location of favNumber , but why is it done this way? I feel like there's a type mismatch here where favNumber is an int and I'm telling scanf that it's a pointer to an int. I thought I wrapped my head around pointers but this is confusing me a bit. Any help would be

问题 I need to create several objects and put them in a list (for which I am using std::vector). Also, I need the list items to point to the addresses of the objects so that the changes I make to the objects are reflected in the list too. But the thing is, every item in the list is pointing to the last object created in the loop. for(int i=0;i<50;i++){ for(int j=0;j<50;j++){ Grass g1; g1.position.x = i; g1.position.y = j; grassList.push_back(&g1); } } The the attributes of grass objects in the

问题 I need to create several objects and put them in a list (for which I am using std::vector). Also, I need the list items to point to the addresses of the objects so that the changes I make to the objects are reflected in the list too. But the thing is, every item in the list is pointing to the last object created in the loop. for(int i=0;i<50;i++){ for(int j=0;j<50;j++){ Grass g1; g1.position.x = i; g1.position.y = j; grassList.push_back(&g1); } } The the attributes of grass objects in the

问题 I need to create several objects and put them in a list (for which I am using std::vector). Also, I need the list items to point to the addresses of the objects so that the changes I make to the objects are reflected in the list too. But the thing is, every item in the list is pointing to the last object created in the loop. for(int i=0;i<50;i++){ for(int j=0;j<50;j++){ Grass g1; g1.position.x = i; g1.position.y = j; grassList.push_back(&g1); } } The the attributes of grass objects in the

问题 this might be a newb question (i am) but i've searched as much as i could to find a solution to the following problem I have the following scenario (heavily distilled of course): class Container { std::vector<Object> obj; }; class Pointers { std::vector<Object*> obj_ptr; }; I have a routine that pushes back an element of type Object to the vector obj in Container then pushes back the pointer to that same element to obj_ptr . the overall idea is that obj_ptr[i] == &obj[i] throughout the life

问题 this might be a newb question (i am) but i've searched as much as i could to find a solution to the following problem I have the following scenario (heavily distilled of course): class Container { std::vector<Object> obj; }; class Pointers { std::vector<Object*> obj_ptr; }; I have a routine that pushes back an element of type Object to the vector obj in Container then pushes back the pointer to that same element to obj_ptr . the overall idea is that obj_ptr[i] == &obj[i] throughout the life

问题 I'm wanting to pass an array into a function. From what I can see, there are 2 ways of doing this: 1. void f (int array[]) { // Taking an array with square brackets } 2. void f (int *array) { // Taking a pointer } Each one is called by: int array[] = {0, 1, 2, 3, 4, 5}; f (array); Is there any actual difference between these 2 approaches? 回答1: In your specific example there is no difference. In more general case one difference between these two approaches stems from the fact that in case of [

问题 I keep getting a read access violation. Here is the code that I have. class List { public: List(); List(const List &copy); ~List(); /*List & operator=(const List &rhs); Record * headPtr() const; void setheadptr(Record * const newhead); bool insertatfront(Record newdata);*/ void importcourselist(); void Loadmasterlist(); void storemasterlist(); Record *makenode(fstream &file); Record *makenode(ifstream &file); private: Record *mHead; Record *mEnd; }; List::List() { mHead = nullptr; mEnd =

问题 I had this argument with some people saying that C out-of-bound pointers cause undefined behavior even if they're not being dereferenced. example: int a; int *p = &a; p = p - 1; the third line here will cause undefined behavior even if p is never dereferenced ( *p is never used). In my opinion, it sounds illogical that C would check if a pointer is out-of-bound without the pointer being used (it's like someone would inspect people on the street to see if they're carrying guns in case they