[boost] Re: typeof

From: Arkadiy Vertleyb (vertleyb_at_[hidden])
Date: 2004-05-03 10:15:17

"David Abrahams" <dave_at_[hidden]> wrote

> > The provided example shows what registration needs to be done to
calculate
> > the type of a lambda functor:
> >
> > #include BOOST_TYPEOF_BEGIN_REGISTRATION()
>
> Where would that line go, in a header file?
>
> > BOOST_TYPEOF_REGISTER_TEMPLATE(tuples::tuple, 2);
> > BOOST_TYPEOF_REGISTER_TEMPLATE(lambda_functor, 1);
> > ....
> > BOOST_TYPEOF_REGISTER_TYPE(placeholder<2>);
> >
> > #include BOOST_TYPEOF_END_REGISTRATION()
>
> Where would that line go, in a source file?  If so, that sounds
> error-prone to me.

Everything would go into one file -- source or header.

The BEGIN_REGISTRATION establishes a unique REGISTRATION_GROUP (using the
counter suggested by Paul Mensonides).  The  REGISTRATION_GROUP is then used
by the registration macros in conjunction with __LINE__ to generate unique
integer identifiers.  The END_REGISTRATION is technicaly not necessary.  It
just undefs the REGISTRATION_GROUP to force other files use the
BEGIN_REGISTRATION (and so avoid potential clashes).

Arkadiy