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From: cok@islsun.Kodak.COM (David Cok)
Newsgroups: comp.lang.c++
Subject: difference between friend and static member function
Message-ID: <1991Feb27.153602.19495@kodak.kodak.com>
Date: 27 Feb 91 15:36:02 GMT
Sender: cok@Kodak.COM
Organization: Eastman Kodak Co., Rochester, NY
Lines: 36

One use of friend declarations is to allow members of other classes (or entire
other classes) access to the internals of a given class.  Aside from that use,

	what can one do with friend functions that one cannot do with
		*static* member functions?

1) static member functions will have conversions applied to all arguments,
just like friends.

2) static member functions can be declared private; friends cannot.  This makes
static members better for functions which are not really part of the interface
but are needed for the implementation (and non-static members are not wanted).

3) static members must be accessed using the class::fcn notation (or using
a dummy object); friends can be called directly.

BUT

4) The compiler (Sun C++ 2.0 on a SparcStation) complains about

	static myclass operator+(myclass,myclass)

saying
	error:  myclass::operator +() must take 0 or 1 arguments

This seems to me to be a bug since there is no implied this argument for a 
static member.  Right or wrong?


Except for the problem in 4 (which only applies to operators) and the 
difference in syntax in 3, it seems friends could generally be replaced by
static members.  Any comments?

David R. Cok
Eastman Kodak Company
cok@Kodak.COM