Question

There is a class A and it has the following operator() implementation:

void A::operator()(...parameters...) const 
{
    // operator body
}

What does this const mean?

Answer 1

Methods in C++ can be marked as const like in the above example to indicate that the function does not modify the instance. To enforce this, the this pointer is of type const A* const within the method.

Normally, the this pointer within a method is A* const to indicate that we cannot change what this points to. That is, so that we cannot do this = new A().

But when the type is const A* const we also cannot change any of the properties.