----- Mensaje original ----- De: François Duranleau Fecha: Domingo, Enero 22, 2006 6:08 am Asunto: Re: [Boost-users] [tuple] no easy access to get function

On Sat, 21 Jan 2006, JOAQUIN LOPEZ MU?Z wrote:

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----- Mensaje original ----- De: Frank Birbacher Fecha: Sábado, Enero 21, 2006 2:29 am Asunto: [Boost-users] [tuple] no easy access to get function

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Today I wanted to std::transform a range of tuples into a sequence of one element. I thought I could just take the address of some tuple::get<N> function. Maybe also specify the Tuple type as template>> parameter [...] I'd rather want to take the address of boost::tuple::get, but the template parameters won't match.

Maybe you forgot the final s in "tuples" when writing

boost::tuples::get

There is a thin wrapper declared in the boost namespace as well. The probleme is elsewhere. The argument to the get function is not a boost::tuple<>, but some base class template. Thus the template arguments of the function are not and an integer and a tuple, but an integer and something else (actually, a cons if you look in the code). To take the address of such a function, you need to bind the integer, as well as HT and TT, not a tuple.

Yep, I see. You're right. Well, you can refer to get<> as follows boost::tuples::get Note that this is not relying on undocumented implementation, so called "const lists" are explained and made public at http://boost.org/libs/tuple/doc/tuple_advanced_interface.html So I'd say you can use the former reference to get safely.

However, I am wondering if there would be a problem to declare the thin wrapper simply like this (example with the const version):

template< int N , typename Tuple > inline typename tuples::access_traits< typename tuples::element< N , Tuples >::type >::const_type get( const Tuple& t ) { return tuples::get< N >( c ) ; }

?

That would also work, but my proposal above is simpler. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users