Question

I am so confused with this code in the book :

typedef int (*healthCalcFunc) (const GameCharacter&)

and I understand that
typedef double* PDouble, means the word PDouble can be used to declare a pointer to double.

But I can’t figure out the meaning of typedef int (*healthCalcFunc) (const GameCharacter&)

Is there anyone can help me to explain this?

Thanks in advance

🙂

Answer 1

typedef int (*healthCalcFunc) (const GameCharacter&);

It introduces a name called healthCalcFunc for a type which describes a function-pointer, taking one parameter of type const GameCharacter& and returning an int.

So this means, if you’ve a function as:

int some_function(const GameCharacter&)
{
    //...
}

Then you can create a pointer-object which would point to the above function as:

healthCalcFunc pfun = some_function;

and then use pfun in place of some_function as:

some_function(args);  /normal call

pfun(args);  //calling using function pointer 
             //it is exactly same as the previous call

And benefit with this approach is that you can pass around pfun (or some_function) to other function as:

void other_function(healthCalcFunc pfun)
{
    //..
    pfun(args); //invoke the function!
    //..
}

healthCalcFunc pfun = some_function;

other_function(some_function);  
other_function(pfun); 

Here other_function will use the function pointer to invoke the function. That way, next time you can pass another function matching the function signature to other_function and other_function will invoke that another function instead.