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

   1 .. Macros/Configuration//BOOST_MPL_LIMIT_METAFUNCTION_ARITY |20
   2
   3 BOOST_MPL_LIMIT_METAFUNCTION_ARITY
   4 ==================================
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     #if !defined(BOOST_MPL_LIMIT_METAFUNCTION_ARITY)
  12     #   define BOOST_MPL_LIMIT_METAFUNCTION_ARITY \\
  13             |idic| \\
  14     /\*\*/
  15     #endif
  16
  17
  18 Description
  19 -----------
  20
  21 ``BOOST_MPL_LIMIT_METAFUNCTION_ARITY`` is an overridable configuration macro
  22 regulating the maximum supported arity of `metafunctions`__ and
  23 `metafunction classes`__. In this implementation of the
  24 library, ``BOOST_MPL_LIMIT_METAFUNCTION_ARITY`` has a default value of 5. To
  25 override the default limit, define ``BOOST_MPL_LIMIT_METAFUNCTION_ARITY`` to
  26 the desired maximum arity before including any library header.
  27 |preprocessed headers disclaimer|
  28
  29 __ `Metafunction`_
  30 __ `Metafunction Class`_
  31
  32
  33 Example
  34 -------
  35
  36 .. parsed-literal::
  37
  38     #define BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS
  39     #define BOOST_MPL_LIMIT_METAFUNCTION_ARITY 2
  40     ``#``\ include <boost/mpl/apply.hpp>
  41
  42     using namespace boost::mpl;
  43
  44     template< typename T1, typename T2 > struct second
  45     {
  46         typedef T2 type;
  47     };
  48
  49     template< typename T1, typename T2, typename T3 > struct third
  50     {
  51         typedef T3 type;
  52     };
  53
  54     typedef apply< second<_1,_2_>,int,long >::type r1;
  55     // typedef apply< third<_1,_2_,_3>,int,long,float >::type r2; // error!
  56
  57
  58 See also
  59 --------
  60
  61 |Macros|, |Configuration|, |BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS|
  62
  63
  64 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
  65    Distributed under the Boost Software License, Version 1.0. (See accompanying
  66    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)