I have a question about what the standard requires for matching a
certain type of function template.

Suppose you have a class with nested classes:

class A
{
public:
  class B {};
  class C {};
};

And you then write functions like:

void f(A::B ab) {}
void f(A::C ac) {}

int main()
{
  A::B a;
  f(a);
}

Then all is well.  If you want to template these two, all is not well:

template<class T> void f(A::T at) {}

In fact things seem to be unwell in a very bizarre manner.  From the
Kuck and Associates C++ compiler (the closest to the draft standard that
I'm aware of) I get the error messages:

"nest.cpp", line 13: error: "f" is not a function or static data member
  template<class T> void f(A::T at) {}
                         ^

"nest.cpp", line 13: error: expected a ";"
  template<class T> void f(A::T at) {}
                           ^
The SGI C++ compiler (7.1beta) give similar errors.

It looks like it is parsing this expression completely differently from
how I would expect.

Is this an aspect of template definitions that is addressed in the
standard?



--
Steve R. Karmesin
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Steve R Karmesin writes:

> class A
> {
> public:
>   class B {};
>   class C {};
> };

[snip]

> template<class T> void f(A::T at) {}

You should think of T as a type, not as a class name.  You would not
refer to such a template as f<B> or f<C>, since B and C are not types.

Instead, you should declare:

template <class T> void f(T at) {}

then use f<A::B> and f<A::C>.

--
Alexandre Oliva
mailto:oliva@dcc.unicamp.br
Universidade Estadual de Campinas, SP, Brasil
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