ceph/src/boost/libs/mpl/doc/src/refmanual/pair.rst

   1 .. Data Types/Miscellaneous//pair |10
   2
   3 pair
   4 ====
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     template<
  12           typename T1
  13         , typename T2
  14         >
  15     struct pair
  16     {
  17         typedef pair type;
  18         typedef T1 first;
  19         typedef T2 second;
  20     };
  21
  22
  23 Description
  24 -----------
  25
  26 A transparent holder for two arbitrary types.
  27
  28
  29 Header
  30 ------
  31
  32 .. parsed-literal::
  33
  34     #include <boost/mpl/pair.hpp>
  35
  36
  37 Example
  38 -------
  39
  40 Count a number of elements in the sequence together with a number of negative
  41 elements among these.
  42
  43 .. parsed-literal::
  44
  45     typedef fold<
  46           vector_c<int,-1,0,5,-7,-2,4,5,7>
  47         , pair< int_<0>, int_<0> >
  48         , pair<
  49               next< first<_1> >
  50             , if_<
  51                   less< _2, int_<0> >
  52                 , next< second<_1> >
  53                 , second<_1>
  54                 >
  55             >
  56         >::type p;
  57
  58     BOOST_MPL_ASSERT_RELATION( p::first::value, ==, 8 );
  59     BOOST_MPL_ASSERT_RELATION( p::second::value, ==, 3 );
  60
  61
  62 See also
  63 --------
  64
  65 |Data Types|, |Sequences|, |first|, |second|
  66
  67
  68 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
  69    Distributed under the Boost Software License, Version 1.0. (See accompanying
  70    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)