Steven Watanabe wrote:
AMDG
Martin Apel <martin.apel <at> simpack.de> writes:
Hi all,
I have two mpl maps like this:
typedef map<pair<int_<1>, int_<42> >, pair<int_<2>, int_<43> >, pair<int_<3>, int_<44> >
Map1;
typedef map<pair<int_<4>, int_<44> >, pair<int_<5>, int_<45> >, pair<int_<6>, int_<46> >
Map2;
I try to join them using "joint_view" as follows:
typedef joint_view<Map1, Map2>::type JointMap;
which works fine. Then I do
std::cout << at<JointMap, int_<2> >::type::value << "\n";
which gives the following compiler error:
error: 'value' is not a member of 'boost::mpl::pair<mpl_::int_<3>, mpl_::int_<44> >'
I tried this with gcc 3.4.6 and 4.2 under Linux, Boost version is 1.34.0. It seems "at" returns the entry after the searched entry, and not only the right half, but the complete pair.
Has anybody got any hints on this? To me it looks like a bug in MPL, but I might be wrong.
joint_veiw is not intended to work that way for maps. It just takes the two sequences and sticks them together. The default implementation of at which is used for joint_view returns the Nth element of the sequence. Since you had the keys in order starting at 1 it appeared that it was adding one. The value of the key is irrelevant in determining the result.
Thanks for the information, Steve. I didn't understand this from the available docs. So is there another way of joining two maps, so they create a single map, that can be used with mpl::at? Regards, Martin ____________ Virus checked: AVKB 17.336 from 12.08.2007