Can't define ++ operator in C++, what's the issue here?

Question

I\'m working through Bjarne Stroustrup\'s The C++ Programming Language and I\'m stuck on one of the examples. Here\'s the code, and aside from whitespace differences and comment

Answer 1

Traffic_light& operator++(Traffic_light& t) is a function with name operator ++. Each function shall be defined outside any other function. So place the definition of the operator before main.