pointers

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 6 years ago . Improve this question I've been trying to learn everything I can about micro-controllers lately. Since this is self-study, it's taken me a while to learn how the things work at the bare metal. Long story short, I don't want to use the AVR libraries in my C code; I want to access

问题 I have an object that I am trying to duplicate for any number of times with some minor changes to that object. I want to store pointers to those duplicated objects in a std::vector . I am using a for loop to try and achieve the result. However, what I notice is that the std::vector<T *> is pointing to the same address after the loop exits. I tried this attempt to duplicate objects with std::string and I see the same effects. Here's my code snippet. int main() { auto name = new std::string(

问题 I am making a stretchy-buffer-like single-file header library for queues in C. I am passing the array as a void* and the size of a single element to one of the functions: void func(void* arr, size_t itemsize); Inside func() I need to do some pointer arithmetic with arr . I can't do arithmetic with void* , so I thought I could create a data type of size itemsize that I could cast arr into, and thus solve my problem. I saw the accepted this question, but would pointer arithmetic on char*[] work

问题 I just solved some tasks about linked lists using Ruby. It was very interesting, but it requires a couple of new lines. Because if I pass head in some function, and change the head of the list, I have to return new head from method and reassign it to the variable. Because if I have a variable and I pass it to method, reassign a inside, outside a dose not changes: it "dose not changes if reassign variable in method" do a = [1,2] def reasign array array = [1] array end assert_equal [1], reasign

问题 I am trying to implement a FIFO. The code compiles without errors but i get segmentation fault when running the program. What is the problem? #include <stdio.h> #include <stdlib.h> struct cell { int element; struct cell *next; }; struct queue { struct cell *front; struct cell *rear; }; void enqueue(int x, struct queue *Q); void dequeue(struct queue *Q); main() /* Manipulation of a linked queue of cells. */ { struct queue *Q; struct cell *q; int i; Q->front=Q->rear=NULL; for(i=0; i<8; i++)

问题 I'm attempting the 'Recover' question on CS50's pset4. It appears that I am able to retrieve all of the images except for 001.jpg. I suspect that this further led to some misalignment with the numbering of the files given that check50 tells me the following:- :) recovers 000.jpg correctly :( recovers middle images correctly 001.jpg not found :( recovers 049.jpg correctly recovered image does not match To be clear, I was able to retrieve 000.jpg, followed immediately by files 002.jpg through

问题 i know that -> is a pointer |= is OR. what is the logical meaning of such line? TIMER0->ROUTELOC0 |= TIMER_ROUTELOC0_CC0LOC_LOC15 回答1: You're ORing in (setting) a value to a register. Your processor has a TIMER0 with a register ROUTELOC0. It likely has a bit that is "CC0LOC_LOC15" I recommend looking at the data sheet for your processor to figure out what that means specifically. 回答2: |= does not mean OR. | means OR. |= is similar to +=, that is A |= B is the equivalent of A = A | B So to

问题 I have struct like this: typedef struct { int x; double *y; int **z; } ind; how could I send pointer like *y and **z via MPI to other processes? I know that many answers said that never send pointers by MPI. But if I cannot change *y to an array because it is used in other part of the main program, what should I do to transfer them through processes via MPI? Especially for **z, how should I do ? Thanks in advance! 回答1: Just following the code from the second example here, I did the following.

问题 I have struct like this: typedef struct { int x; double *y; int **z; } ind; how could I send pointer like *y and **z via MPI to other processes? I know that many answers said that never send pointers by MPI. But if I cannot change *y to an array because it is used in other part of the main program, what should I do to transfer them through processes via MPI? Especially for **z, how should I do ? Thanks in advance! 回答1: Just following the code from the second example here, I did the following.

问题 so I have the file Countries.c which contains: typedef struct City* pCity; typedef struct Country* pCountry; typedef struct Territory* pTerritory; struct City{ char* name; char* food; int population; }; struct Country{ char *name; int numCities; pCity cities; pTerritory countryTerr; }; struct Territory{ int x1; int x2; int y1; int y2; }; void deleteCountry(pCountry country){ if(country != NULL){ int num_of_cities = country->numCities; for(int i = 0 ; i<num_of_cities; i++){ if (country->cities