Re: [Boost-users] [MPL] Fold a vector of pairs

14 Mar 2012


      AMDG

On 03/14/2012 01:25 AM, Peter Nyssen wrote:
...
<snip>
    typedef typename mpl::fold<
        initial_vector,
        mpl::pair, mpl::vector<> >,
        mpl::if_<
            is_tag1mpl::_2 >,
            mpl::push_back<
                mpl::firstmpl::_1,
                mpl::secondmpl::_2
            >,
            mpl::push_back<
                mpl::secondmpl::_1,
                mpl::secondmpl::_2
            >
        >
    >::type sorted_pair;
<snip>
//-------------------------------------
$ g++4 -Wall -I ../boost/ -o test test.cpp
test.cpp: In function 'int main()':
test.cpp:28: error: using 'typename' outside of template
This should be obvious.
...
../boost/boost/mpl/pair.hpp:56: error: no type named 'second' in 'struct
boost::mpl::v_item, boost::mpl::vector
The state should be a pair of vectors, but the
fold operation produces a single vector.

In Christ,
Steven Watanabe