In article <22749@alice.att.com>, bs@alice.att.com (Bjarne Stroustrup) writes:
>
> [...] Then try this:
>
> #include<iostream.h>
>     template <class T, int sz>
>   class stack {
>        friend ostream& operator<< (ostream& os, stack<T,sz>);
>    public:
>        stack () { index = 0; }
>        void push (T elem) { tab[index++] = elem; }
>        T pop (void) { return tab[--index]; }
>    private:
>        T tab[sz];
>        int index;
>    };
>
>    template <class T>
>    ostream& operator<< (ostream& os, T st)
>    {
>        for (int i=0; i<st.index; i++)
>          os << st.tab[i] << endl;
>        return os;
>    }
>
> It works.

Yes, it does. But now try this: replace the signature of pop() with one that
takes a default argument:

        T pop (int x=5) { return tab[--index]; }

and run the code through your AT&T 3.0 compiler. It does NOT work anymore.
Please refer to article #23736 of comp.lang.c++, in which I presented the
problem in detail and offered a similar piece of code to support the case.

For short, if a templated class contains member functions with one or more
default arguments, and is in a 1:1 relationship with a friend function
whose argument(s) is/are templated, AT&T 3.0 complains with the message:
"error:  function templates do not support default arguments".

I seriously doubt the validity of this error message, and I hope somebody
from AT&T can provide a definite explanation. If what I have encountered
is indeed a bug, is it a known one? Will a patch be available in the near
future? For the time being, how can one avoid it while still using default
arguments and 1:1 relationships with templated friend functions?

-Chris Barghiel

P.S. I am told that BC++ compiles the code without making any complaints.
--
Cristin Barghiel  DC 2134,  (519)885-1211  x3389
cbarghie@watcgl.waterloo.edu Dept. of Computer Science
cbarghie@watcgl.uwaterloo.ca University of Waterloo, Canada