How to assign double* value to double* queue[i]?

Question

I would like to assign integer 1 to double* queue[i].. I need to convert int 1 to double* type value first before I can assign it to queue[i].. How to code this?

Answer 1

I would like to assign integer 1 to double* queue[i]

I think you meant to add the value 1 into your queue:

queue[i] = new double(1.0);

Assigning a direct address is a different story.

I need to convert int 1 to double* type value first before I can assign it to queue[i]

That's not how your dynamic queue works. It stores the address of newly allocated memory for every double. The new operator is used for this purpose and it will return the necessary pointer, you just need to do the dynamic memory allocation properly.

Answer 2

Do you want to assign a direct address to a pointer variable? You had better use & operator or +, ++ operators on known functions or variables to get the addresses. It's unsafe and not recommended to hardcode address in code. Each time the program is loaded into memory, it could be a different memory space, so the hardcoded address will cause segmentation fault.

See the following example. Either queue[1] assignment or queue[2] assignment is not recommended.

#include <stdio.h>
#define MAX_SIZE 10

void print(double *p, int i)
{
    printf("queue[%d]=%p\t*queue[%d]=%.2f\n", i, p, i, *p);
}

int main()
{
    double *queue[MAX_SIZE];
    double dval = 3.5f;
    int ival = 1;

    queue[0] = &dval;
    print(queue[0], 0); 
    // queue[0]=0x7ffee2bfca20  *queue[0]=3.50

    queue[1] = &ival;
    print(queue[1], 1); 
    // queue[1]=0x7ffee2bfca1c  *queue[1]=0.00

    queue[2] = ((double *)1);
    print(queue[2], 2); 
    // zsh: segmentation fault

    return 0;
}