What are function objects in C++ and how do I use them?

What are function objects in C++?

Function objects, or functors, are objects that can be called as if they were functions. They are instances of classes that overload the function call operator.

Can you give me an example of a function object?

Sure! Here's a simple example:

class Adder {
public:
    int operator()(int a, int b) {
        return a + b;
    }
};

Adder add;
int result = add(5, 3); // result will be 8

How do function objects compare to regular functions?

Function objects can maintain state and can be more flexible than regular functions. They can also be passed to algorithms in the STL.

Are there any performance benefits to using function objects?

Yes, function objects can be more efficient than regular functions, especially in cases where they can be inlined by the compiler, reducing overhead.