when I look at this website http://www.parashift.com/c++-faq-lite/operator-overloading.html,
I don't quite understand for the section 13.14 about prefix++ and postfix++.
Number x = /* ... */;
++x; // calls Number::operator++(), i.e., calls x.operator++()
x++; // calls Number::operator++(int), i.e., calls x.operator++(0)
why ++x is calling x.operator++() while x++ is calling calls x.operator++(0)?