Hello, Operator

ops.cpp

int i = 0;
++ ++ i; // no problem
i ++ ++; // doesn't compile

/*
 * It has to do with how these operators work and in particular their return types. The prefix operator returns
 * the value after modification. The postfix operator returns the value before modification. But how does it do
 * that? These operators date back to C at least. It's not some background task that happens after the operator
 * finishes. The prefix operator returns a reference to the same thing (int, object, etc.). The postfix operator
 * returns a temporary value. It stores the value in a separate location, modifies the value at the original
 * location and then returns the stored value as a temporary. Hence the return value of the postfix operator
 * can't be modified. It's not an lvalue (a value that can appear on the left-hand side of an assignment).
 * The prefix operator gives you back a reference to the same modified thing without making a copy. This reference
 * can continue to be modified.
 *
 * The signatures of these operators:
 */

int& operator++(); // prefix
int operator++(int); // postfix