jeffw@CSSUN.TAMU.EDU (Jeffrey A Waller) (10/10/89)
I believe that I have found a compiler bug, however, it may be a
difference from the AT&T compiler that was not documented in the user's guide.
Just the same, though, I think that the compiler incorrectly flagged an error
whatever the definition of the compiler is. The version of the compiler is
1.35.0, and is running on a sun 3/260 running operating system version 4.0.3,
although I doubt that the version of the op system is the cause. I have
included the source code, with the the name of the file as the subject of the
mail message. The error occurs on line 28 of Stringnode.c, and is
Stringnode.c:28: method `long unsigned int node::IdentifySelf() is protected
However, Stringnode is declared as
class Stringnode: public node
so IdentifySelf sould be usable by Stringnode. This is especially true in
view of the declaration of IdentifySelf():
class node
{ .
.
.
protected:
virtual unsigned int IdentifySelf();
.
.
.
};
The inportant part being that IdentifySelf() is virtual.
On another topic, in the user's Guide you asked for any one to write
in about static member functions. Extending the idea of static data members
(being the same for all instances of the class) static member function could be
the same with the proviso the they can only operate on static data members.
This might be a way to have static class data members with constructors,
although I really don't know the reason for this limitation aside from the
need to call the constructors before the main program (and hence certian values
may not be initialized yet). But, the main advantage for static member
functions is that since their functionality is independant on the instance of
the class, they do NOT need to be passed a pointer to the intance of the class.
An irksome drawback I had over the summer was interfacing old C code with C++
classes; member functions could not be called directly from a C module due to
the hidden variable, and also the renaming convention. Static member functions
may be a way around this, as long as they are not overloaded.
-Jeff Waller
P.S. If for some reason the mail address is lost: jeffw@cssun.tamu.edu
P.S.S. If you can't get back at all via mail
snail:
Jeff Waller
1501 Harvey Rd, Apt 650
College Station, TX 77840
or
Jeff Waller
Department of Computer Science
Texas A&M University
College Station, TX 77840
tiemann@LURCH.STANFORD.EDU (Michael Tiemann) (10/10/89)
The problem you found with protected is commonly though a bug, but it is the 2.0 way of implementing protected, which is different than the original, 1.2 way of doing it. I have implemented static member functions, in version 1.36.0, which is currently in test release. Watch this newsgroup for the next announcement of a test release, or watch info-g++ for the announcement of the official release. Michael