Ivor Horton's Beginning Visual C++ 2012

RETURNING VALUES FROM A FUNCTION

All the example functions that you have created have returned a single value. Is it possible to return anything other than a single value? Well, not directly, but as I said earlier, the single value returned need not be a numeric value; it could also be an address, which provides the key to returning any amount of data. You simply use a pointer. Unfortunately, this also is where the pitfalls start, so you need to keep your wits about you for the adventure ahead.

Returning a Pointer

Returning a pointer value is easy. A pointer value is just an address, so if you want to return the address of some variable value, you can just write the following:

return &value;                     // Returning an address

As long as the function header and function prototype indicate the return type appropriately, you have no problem — or at least, no apparent problem. Assuming that the variable value is of type double, the prototype of a function called treble, which might contain the preceding return statement, could be as follows:

double* treble(double data);

I have defined the parameter list arbitrarily here.

So let’s look at a function that returns a pointer. It’s only fair that I warn you in advance — this function doesn’t work, but it is educational. Let’s assume that you need a function that returns a pointer to a memory location containing three times its argument value. Our first attempt to implement such a function might look like this:

// Function to treble a value - mark ...