Understanding the Syntax
	• This declaration allows us to apply the subtraction operator to two objects of the same class and returns an object of that class as an rvalue. • The italics represent my recommendations, if followed, result in behavior that more closely matches that of the built-in types. • Since the predefined behavior of the subtraction operator does not modify its two operands, the formal arguments of the operator- function should be specified either as constant references or passed by value.