How can I call a function using a function pointer?

Question

Suppose I have these three functions:

bool A();
bool B();
bool C();

How do I call one of these functions conditionally using a function poi

Answer 1

Slightly different approach:

bool A() {...}
bool B() {...}
bool C() {...}

int main(void)
{
  /**
   * Declare an array of pointers to functions returning bool
   * and initialize with A, B, and C
   */
  bool (*farr[])() = {A, B, C};
  ...
  /**
   * Call A, B, or C based on the value of i
   * (assumes i is in range of array)
   */
  if (farr[i]()) // or (*farr[i])()
  {
    ...
  }
  ...
}

Answer 2

This has been more than adequately answered, but you may find this useful: The Function Pointer Tutorials. It is a truly comprehensive treatment of the subject in five chapters!

Answer 3

bool (*FuncPtr)()

FuncPtr = A;
FuncPtr();

If you want to call one of those functions conditionally, you should consider using an array of function pointers. In this case you'd have 3 elements pointing to A, B, and C and you call one depending on the index to the array, such as funcArray0 for A.

Answer 4

The best way to read that is the clockwise/spiral rule by David Anderson.

Answer 5

I usually use typedef to do it, but it may be overkill, if you do not have to use the function pointer too often..

//assuming bool is available (where I come from it is an enum)

typedef bool (*pmyfun_t)();

pmyfun_t pMyFun;

pMyFun=A; //pMyFun=&A is actually same

pMyFun();

Answer 6

Calling a function through a function pointer

float add(int, float), result;

int main()
{
    float (*fp)(int, float);
    float result;
    fp = add;
    result = add(5, 10.9);    // Normal calling
    printf("%f\n\n", result);

    result = (*fp)(5, 10.9);  // Calling via a function pointer
    printf("%f\n\n", result);

    result = (fp)(5, 10.9);   // Calling via function pointer. The
                              // indirection operator can be omitted

    printf("%f", result);
    getch();
}

float add(int a, float b)
{
    return a+b;
}

>

Output

15.90000
15.90000
15.90000