C++ Passing Pointers to Functions
C++ allows you to pass pointers to functions by simply declaring the function parameters as pointer types.
In the following example, we pass a pointer to an unsigned long to the function, and change this value inside the function:
Example
#include <iostream>
#include <ctime>
using namespace std;
// When writing functions, it is a good habit to declare the function first, then define it
void getSeconds(unsigned long *par);
int main ()
{
unsigned long sec;
getSeconds( &sec );
// Output the actual value
cout << "Number of seconds :" << sec << endl;
return 0;
}
void getSeconds(unsigned long *par)
{
// Get the current seconds
*par = time( NULL );
return;
}
When the above code is compiled and executed, it produces the following results:
Number of seconds :1294450468
Functions that can accept pointers as parameters can also accept arrays as parameters, as shown below:
Example
#include <iostream>
using namespace std;
// Function declaration
double getAverage(int *arr, int size);
int main ()
{
// An integer array with 5 elements
int balance[5] = {1000, 2, 3, 17, 50};
double avg;
// Pass a pointer to an array as an argument
avg = getAverage( balance, 5 ) ;
// Output the return value
cout << "Average value is: " << avg << endl;
return 0;
}
double getAverage(int *arr, int size)
{
int i, sum = 0;
double avg;
for (i = 0; i < size; ++i)
{
sum += arr[i];
}
avg = double(sum) / size;
return avg;
}
When the above code is compiled and executed, it produces the following results:
Average value is: 214.4other extensions