overloading operator

As I am newbie to C++, I am confused by the overloading issues. Everyone
says that the four operators can only be overloaded with class member
functions instead of global (friend) functions: (), [], ->, =. I wonder
why there is such a restriction.

Some tutorials say that 'new' and 'delete' can only be overloaded with
static member functions, others say that all overloading function should
be non-static. Then what is the fact, and why?

I'd appreciate it very much if anyone can answer me or lead me to a
detail explanation.

re: overloading operator

Jerry Fleming wrote:If there wasn't, how could you specify the left hand side of an expression?

All unary operators have to be class members.
You can provide a global operator new(), or a class specific one which
has to be a class member.
All this is well covered in Stroustrup.

--
Ian Collins.

re: overloading operator

Ian Collins wrote:Not really, you can do overload unary "-" or binary "-" by using a
friend function.

re: overloading operator

* Ian Collins:In the same way as with other operators: as an argument.

E.g., if it weren't for the language restriction,

MyClass& operator=( MyClass& lhs, MyClass const& rhs ) { ... }

I don't know why that isn't allowed, but one common feature is that
these operators are not meaningful for enum types, only for class types.

Sorry, that's incorrect.

§13.5.1 "A prefix unary operator shall be implemented by a non-static
member function (9.3) with no parameters or a non-member function with
one parameter. Thus, for any prefix unary operator @, @x can be
interpreted as either x.operator@ or operator@(x)."

And ditto for postfix ones.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

re: overloading operator

Alf P. Steinbach wrote:Oops, thanks for the correction.

--
Ian Collins.

re: overloading operator

On 2006-10-23 14:50, Ian Collins wrote:Thanks everybody. I have just find a post on overloading =, and that
seems to make it clear: the four operators are disallowed for
overloading with friends because otherwise they might lead to error. To
quote Stroustrup:

"Only a few assumptions are made about the meaning of a userdefined
operator. In particular, operator=, operator[], operator(), and
operatormust be non-static member functions; this
ensures that their first operands will be lvalues (§4.9.6)."

As to the question of "new" and "delete", they are implicitly static if
defined within a class.

Am I right?