boost/utility/base_from_member.hpp

   1 //  boost utility/base_from_member.hpp header file  --------------------------//
   2
   3 //  Copyright 2001, 2003, 2004 Daryle Walker.  Use, modification, and
   4 //  distribution are subject to the Boost Software License, Version 1.0.  (See
   5 //  accompanying file LICENSE_1_0.txt or a copy at
   6 //  <http://www.boost.org/LICENSE_1_0.txt>.)
   7
   8 //  See <http://www.boost.org/libs/utility/> for the library's home page.
   9
  10 #ifndef BOOST_UTILITY_BASE_FROM_MEMBER_HPP
  11 #define BOOST_UTILITY_BASE_FROM_MEMBER_HPP
  12
  13 #include <boost/preprocessor/arithmetic/inc.hpp>
  14 #include <boost/preprocessor/repetition/enum_binary_params.hpp>
  15 #include <boost/preprocessor/repetition/enum_params.hpp>
  16 #include <boost/preprocessor/repetition/repeat_from_to.hpp>
  17
  18
  19 //  Base-from-member arity configuration macro  ------------------------------//
  20
  21 // The following macro determines how many arguments will be in the largest
  22 // constructor template of base_from_member.  Constructor templates will be
  23 // generated from one argument to this maximum.  Code from other files can read
  24 // this number if they need to always match the exact maximum base_from_member
  25 // uses.  The maximum constructor length can be changed by overriding the
  26 // #defined constant.  Make sure to apply the override, if any, for all source
  27 // files during project compiling for consistency.
  28
  29 // Contributed by Jonathan Turkanis
  30
  31 #ifndef BOOST_BASE_FROM_MEMBER_MAX_ARITY
  32 #define BOOST_BASE_FROM_MEMBER_MAX_ARITY  10
  33 #endif
  34
  35
  36 //  An iteration of a constructor template for base_from_member  -------------//
  37
  38 // A macro that should expand to:
  39 //     template < typename T1, ..., typename Tn >
  40 //     base_from_member( T1 x1, ..., Tn xn )
  41 //         : member( x1, ..., xn )
  42 //         {}
  43 // This macro should only persist within this file.
  44
  45 #define BOOST_PRIVATE_CTR_DEF( z, n, data )                            \
  46     template < BOOST_PP_ENUM_PARAMS(n, typename T) >                   \
  47     explicit base_from_member( BOOST_PP_ENUM_BINARY_PARAMS(n, T, x) )  \
  48         : member( BOOST_PP_ENUM_PARAMS(n, x) )                         \
  49         {}                                                             \
  50     /**/
  51
  52
  53 namespace boost
  54 {
  55
  56 //  Base-from-member class template  -----------------------------------------//
  57
  58 // Helper to initialize a base object so a derived class can use this
  59 // object in the initialization of another base class.  Used by
  60 // Dietmar Kuehl from ideas by Ron Klatcho to solve the problem of a
  61 // base class needing to be initialized by a member.
  62
  63 // Contributed by Daryle Walker
  64
  65 template < typename MemberType, int UniqueID = 0 >
  66 class base_from_member
  67 {
  68 protected:
  69     MemberType  member;
  70
  71     base_from_member()
  72         : member()
  73         {}
  74
  75     BOOST_PP_REPEAT_FROM_TO( 1, BOOST_PP_INC(BOOST_BASE_FROM_MEMBER_MAX_ARITY),
  76      BOOST_PRIVATE_CTR_DEF, _ )
  77
  78 };  // boost::base_from_member
  79
  80 }  // namespace boost
  81
  82
  83 // Undo any private macros
  84 #undef BOOST_PRIVATE_CTR_DEF
  85
  86
  87 #endif  // BOOST_UTILITY_BASE_FROM_MEMBER_HPP