TITLE: Is global operator & allowable?


RESPONSE: jamshid (Jamshid Afshar), 24 Jun 94


The following code is legal and allowed by our compilers:
----
class Proxy {
public:
    class Foo* f;
};

class Foo {};

// nonmember function
const Foo* operator&(const Proxy& x) { return x.f; }
----

D&E 3.6.2 has a good discussion of why operator=() must be a member on
p82: "The original idea was to allow every operator to be either a
member or a global function. [...]  The problem is that unless
operator=() is a member, a program can have two different
interpretations of = dependent on the location of in the source code
[...example...].  in the original design of C++, I restricted
operators [], (), and -> to be members.  It seemed a harmless
restriction ...  However, it is probably a case of unnecessary
nannyism".  

[...]

[ Jam thought that the table below would be a good addition to this.
  (from ARM 12.3c p306) -adc ]


12.3c Summary of Member, Friend, and Special Functions

--------------------------------------------------------------------------
			can be	can have	member		generated
		inher	virt	ret typ		or friend	by default
--------------------------------------------------------------------------
constructor	no	no	no		member		yes
destructor	no	yes	no		member		yes
conversion	yes	yes	no		member		no
= 		no	yes	yes		member		yes
()		yes	yes	yes		member		no
[]		yes	yes	yes		member		no
->		yes	yes	yes		member		no
op=		yes	yes	yes		either		no
new		yes	no	void*		static member	no
delete		yes	no	void		static member	no
other operator	yes	yes	yes		either		no
other member	yes	yes	yes		member		no
friend		no	no	yes		friend		no