What C++ operator is being overloaded here?

Question

What operator is this code overloading? It doesn't look like the right syntax for the () operator.

class Example
{
public:
  operator bool() const;
...
};

It's used to simulate a boolean member variable, like this:

class Container
{
  public:
    Example ex;
}

void func()
{
  Container c;

  if (c.ex)
  {
  ...
  }
}

Note that ex is used without the parentheses you'd expect from overloading the () operator.

Answer 1

This is operator bool, the implicit conversion operator which allows your class to be used in a boolean context (like if).

Answer 2

That is a user-defined conversion.
It defines a user-defined conversion function that participates in all implicit and explicit conversions.