C++ Function Pointer vs Function Object

What is the difference between a function pointer and a function object in C++?

A function pointer is a variable that stores the address of a function, allowing you to call it indirectly. A function object, or functor, is an object that can be called as if it were a function, typically by overloading the operator(). They serve similar purposes but have different use cases.

Can you give me an example of each?

Sure! Here's a simple example:

Function Pointer:

void myFunction() { std::cout << "Hello from function!"; }
void (*funcPtr)() = myFunction;
funcPtr(); // Calls myFunction

Function Object:

class MyFunctor {
public:
    void operator()() { std::cout << "Hello from functor!"; }
};
MyFunctor functor;
functor(); // Calls operator() of MyFunctor

When should I use a function object instead of a function pointer?

Function objects are more flexible; they can maintain state and can be used with STL algorithms that require callable objects. If you need to pass additional data or maintain state, use a function object.

Are there performance differences between the two?

In general, function pointers can be slightly faster due to their simplicity, but function objects can be optimized by the compiler and may offer better performance in complex scenarios. It often depends on the specific use case.