On Nov 13, 2006, at 4:08 PM, David Abrahams wrote:
Matthias Troyer <troyer@phys.ethz.ch> writes:
On Nov 12, 2006, at 6:46 PM, David Abrahams wrote:
Matthias Troyer <troyer@phys.ethz.ch> writes:
template <class Ostream, class Id> typename enable_if< is_base_of< identifier< typename Id::value_type, Id >, Id >, Ostream & >::type operator<<( Ostream & os, const Id & id ) { return os << id.value(); }
which breaks all of my codes, since I have a type Id, that has a type member Id::value_type which is an abstract base class. My compiler (Apple gcc-4.0) now tries to instantiate identifier< typename Id::value_type, Id >, which fails because Id::value_type is abstract, and the compiler aborts with an error message.
Is that a compiler bug?
Maybe you're actually saying that you don't have a type called Id; you just have
shared_ptr<T>.
Yes, sorry if I was unclear.
Fair enough. I think the correct thing to do is put the definition of class template identifier in its own subnamespace of boost along with the streaming operator (no need for enable_if). It could then be imported into namespace boost with a using declaration...
Frankly, I'm not sure that reserving the name boost::identifier is the right thing to do, especially if it's in a detail header. Is this a public interface, or not? If not, it shouldn't be directly in boost::. If so, it should be documented somewhere and it should have passed through a review. Did it?
It was checked in on November 3rd by Beman Dawes, and I recently realized that now my codes are broken becuase of it. Matthias