Re: [Boost-users] [MPL] mpl::at for AssociativeSequence

On Tue, Jun 12, 2012 at 9:11 AM, wrote:

Hi list,

I'm trying to use the version of mpl::at with three template parameters, as specified here ( http://www.boost.org/doc/libs/1_46_0/libs/mpl/doc/refmanual/at.html)

But I'm getting a compiler error saying 'boost::mpl::at' : too many template arguments.

What am I doing wrong?

#include #include #include #include #include

using namespace boost; using namespace boost::mpl;

typedef map< pair , pair , pair,char[17]> , pair > m;

BOOST_MPL_ASSERT_RELATION( size<m>::value, ==, 4 ); BOOST_MPL_ASSERT_NOT(( empty<m> ));

BOOST_MPL_ASSERT(( is_same< at::type, unsigned > )); BOOST_MPL_ASSERT(( is_same< at >::type, char[17] > )); BOOST_MPL_ASSERT(( is_same< at::type, bool > )); BOOST_MPL_ASSERT(( is_same< at::type, void_ > ));

BOOST_MPL_ASSERT(( is_same< at::type, void_ > )); // fails!

It seems there is a discrepancy between the documentation and the code; if you take a look at boost/mpl/at_fwd.hpp, it forward declares boost::mpl::at with only 2 template parameters :( Please file a trac ticket, and I'll try to find out what the correct resolution is on the developer's list. - Jeff