使用c复制超出源最后一个元素的数组和指针

Question

Would it be possible to initialize and array of double and then copy the contents into another array. The program should use a function using pointer notation to copy the original source array.

Example of the function call I am supposed to use would be copy_ptrs(copy, source, and a pointer to the element following the last element of the source.)

Here is my main for reference

int main() 
{
    int i, num; 
    double source[MAX];
    double target1[MAX];
    double target2[MAX];
    double target3[MAX];


    printf("\nEnter number of elements to be read into the array: ");
    scanf("%d", &num);

    printf("\nEnter the values below (press enter after each entry)\n");

    for (i = 0; i < num; i++) 
    {
            scanf("%lf", &source[i]);
    }

    copy_arr(target1, source, num);
    copy_ptr(target2, source, num);
    copy_ptrs(target3, source, source + num);//This is how I was instructed to call the function.


    printf("\n\nCopying Complete!\n");

    return 0;
}

Here is my pointer notation function for a simple copy

void copy_ptr(double target2[], double source[], int num)
{
    int i;
    double *p, *q;

    p = source;
    q = target2;

    for (i = 0; i < num; i++)
    {
            *q = *p;
        q++;
        p++;
    }

    printf("\n\n***The second function uses pointer notation to copy the elements***\n");
    printf("===================================================================\n");
    q = target2;

    for(i = 0; i < num; i++)
    {

        printf("\n              Pointer_Notation_Copy[%d] = %.2lf",i, *q++);
    }
}

Here is the other function to copy the source array using array notation

void copy_ptr(double target2[], double source[], int num)
{
    int i;
    double *p, *q;

    p = source;
    q = target2;

    for (i = 0; i < num; i++)
    {
            *q = *p;
        q++;
        p++;
    }

    printf("\n\n***The second function uses pointer notation to copy the elements***\n");
    printf("===================================================================\n");
    q = target2;

    for(i = 0; i < num; i++)
    {

        printf("\n              Pointer_Notation_Copy[%d] = %.2lf",i, *q++);
    }
}

When I try to add a 3rd function to satisfy the assignment I get stuck. How do I take a pointer to the element following the last element of the source?

void copy_ptrs(double target3[], double source[], int num)
{
    int i;
    double *p, *q;

    p = source;
    q = target3;

    for (i = 0; i < num; i++)
    {
            *q = *p;
        q++;
        p++;
    }

    printf("\n\n***The third function uses pointer notation to copy the elements + the number of elements read in?***\n");
    printf("===================================================================\n");
    q = target3;

    for(i = 0; i < num; i++)
    {

        printf("\n              Pointer_Notation_Copy[%d] = %.2lf",i, *q++);
    }
}

Answer 1

Your statment:

copy_ptrs(copy, source, and a pointer to the element following the last element of the source.)

and code:

void copy_ptr(double target2[], double source[], int num)

don't match.

Your call

copy_ptrs(target3, source, source + num);

does not match the function definition either.

You can change the function to:

void copy_ptr(double target2[], double* source, double* end)

to make it match with your statement and function call.

Then, you'll have to change the implementation to:

void copy_ptr(double target[], double* source, double* end)
{
   int i = 0;
   int num = end - source;
   double* p = source;
   double* q = target;

   for ( ; p != end; ++p, ++q)
   {
      *q = *p;
   }

   printf("\n\n***The second function uses pointer notation to copy the elements***\n");
   printf("===================================================================\n");

   q = target;
   for ( i = 0; i < num; ++i, ++q )
   {
      printf("\n              Pointer_Notation_Copy[%d] = %.2lf", i, *q);
   }
}