From page 31 (PDF):
This function is a member function or method. It accepts self as a parameter,
which is automatically passed into the function when you reference an
instance of the struct (e.g. my_visitor.greet()) with the contents of that specific
structure instance.
My apologies if I misunderstood, but appears that this may have been the intended sentence:
This function is a member function or method. It accepts self as a parameter,
which is automatically passed into the function when you reference an
instance of the struct (e.g. my_visitor.greet_visitor()) with the contents of that specific
structure instance.
I’m really enjoying the book thus far. Thanks for writing it!