pair

Synopsis

template<
      typename T1
    , typename T2
    >
struct pair
{
    typedef pair type;
    typedef T1 first;
    typedef T2 second;
};

Description

A transparent holder for two arbitrary types.

Header

#include <boost/mpl/pair.hpp>

Example

Count a number of elements in the sequence together with a number of negative elements among these.

typedef fold<
      vector_c<int,-1,0,5,-7,-2,4,5,7>
    , pair< int_<0>, int_<0> >
    , pair<
          next< first<_1> >
        , if_<
              less< _2, int_<0> >
            , next< second<_1> >
            , second<_1>
            >
        >
    >::type p;

BOOST_MPL_ASSERT_RELATION( p::first::value, ==, 8 );
BOOST_MPL_ASSERT_RELATION( p::second::value, ==, 3 );

See also

Data Types, Sequences, first, second