boost/boost/preprocessor/list/fold_right.hpp

   1 #ifndef BOOST_PREPROCESSOR_LIST_FOLD_RIGHT_HPP
   2 #define BOOST_PREPROCESSOR_LIST_FOLD_RIGHT_HPP
   3
   4 /* Copyright (C) 2001
   5  * Housemarque Oy
   6  * http://www.housemarque.com
   7  *
   8  * Permission to copy, use, modify, sell and distribute this software is
   9  * granted provided this copyright notice appears in all copies. This
  10  * software is provided "as is" without express or implied warranty, and
  11  * with no claim as to its suitability for any purpose.
  12  *
  13  * See http://www.boost.org for most recent version.
  14  */
  15
  16 #include <boost/preprocessor/list/reverse.hpp>
  17
  18 /** <p>Iterates <code>OP(D,X,STATE)</code> for each element <code>X</code> of the
  19 list <code>LIST</code> (from the right or the end of the list).</p>
  20
  21 <p>In other words, expands to:</p>
  22
  23 <pre>
  24 OP
  25 ( D
  26 , BOOST_PP_LIST_AT(LIST,0)
  27 , ... OP
  28       ( D
  29       , BOOST_PP_LIST_AT(LIST,BOOST_PP_SUB(BOOST_PP_LIST_SIZE(LIST),2))
  30       , OP
  31         ( D
  32         , BOOST_PP_LIST_AT(LIST,BOOST_PP_SUB(BOOST_PP_LIST_SIZE(LIST),1))
  33         , STATE
  34         )
  35       ) ...
  36 )
  37 </pre>
  38
  39 <p>For example,</p>
  40
  41 <pre>
  42 #define TEST(D,X,STATE) BOOST_PP_CAT(STATE,X)
  43 BOOST_PP_LIST_FOLD_RIGHT(TEST,_,BOOST_PP_TUPLE_TO_LIST(3,(A,B,C)))
  44 </pre>
  45
  46 <p>expands to:</p>
  47
  48 <pre>
  49 _CBA
  50 </pre>
  51
  52 <h3>Note</h3>
  53 <ul>
  54   <li>Folding, or accumulation, is a very general pattern of computation.
  55       Most list operations can be implemented in terms of folding.</li>
  56 </ul>
  57
  58 <h3>Test</h3>
  59 <ul>
  60   <li><a href="../../test/list_test.cpp">list_test.cpp</a></li>
  61 </ul>
  62 */
  63 #define BOOST_PP_LIST_FOLD_RIGHT(OP,LIST,STATE) BOOST_PP_LIST_FOLD_RIGHT_D(0,OP,LIST,STATE)
  64
  65 /** <p>Can be used inside BOOST_PP_WHILE() (see for an explanation of the D parameter).</p>
  66
  67 <h3>Note</h3>
  68 <ul>
  69   <li>BOOST_PP_LIST_FOLD_RIGHT_D() implements automatic recursion. You
  70       can use a fold in the OP macro.</li>
  71 </ul>
  72 */
  73 #if 0
  74 #  define BOOST_PP_LIST_FOLD_RIGHT_D(D,OP,LIST,STATE)
  75 #endif
  76
  77 #define BOOST_PP_LIST_FOLD_RIGHT_D\
  78   BOOST_PP_AUTO_REC_CAT1(BOOST_PP_LIST_FOLD_RIGHT_D,BOOST_PP_LIST_FOLD_LEFT_D_AUTO_REC1(BOOST_PP_AUTO_REC_ID,(1)))
  79 #define BOOST_PP_LIST_FOLD_RIGHT_DBOOST_PP_LIST_FOLD_LEFT_D_AUTO_REC1(M,P)\
  80   BOOST_PP_AUTO_REC_CAT2(BOOST_PP_LIST_FOLD_RIGHT_D,BOOST_PP_LIST_FOLD_LEFT_D_AUTO_REC2(BOOST_PP_AUTO_REC_ID,(2)))
  81 #define BOOST_PP_LIST_FOLD_RIGHT_DBOOST_PP_LIST_FOLD_LEFT_D_AUTO_REC2(M,P)\
  82   BOOST_PP_AUTO_REC_CAT3(BOOST_PP_LIST_FOLD_RIGHT_D,BOOST_PP_LIST_FOLD_LEFT_D_AUTO_REC3(BOOST_PP_AUTO_REC_ID,(3)))
  83 #define BOOST_PP_LIST_FOLD_RIGHT_DBOOST_PP_LIST_FOLD_LEFT_D_AUTO_REC3(M,P)\
  84   (TOO MANY NESTED FOLDS!)
  85
  86 #define BOOST_PP_LIST_FOLD_RIGHT_D1(D,O,L,S) BOOST_PP_TUPLE_ELEM(2,1,BOOST_PP_LIST_FOLD_LEFT_D(D,BOOST_PP_LIST_FOLD_RIGHT_O1,(O,S),BOOST_PP_LIST_REVERSE_D(D,L)))
  87 #define BOOST_PP_LIST_FOLD_RIGHT_D2(D,O,L,S) BOOST_PP_TUPLE_ELEM(2,1,BOOST_PP_LIST_FOLD_LEFT_D(D,BOOST_PP_LIST_FOLD_RIGHT_O2,(O,S),BOOST_PP_LIST_REVERSE_D(D,L)))
  88 #define BOOST_PP_LIST_FOLD_RIGHT_D3(D,O,L,S) BOOST_PP_TUPLE_ELEM(2,1,BOOST_PP_LIST_FOLD_LEFT_D(D,BOOST_PP_LIST_FOLD_RIGHT_O3,(O,S),BOOST_PP_LIST_REVERSE_D(D,L)))
  89
  90 #define BOOST_PP_LIST_FOLD_RIGHT_O1(D,OS,X) (BOOST_PP_TUPLE_ELEM(2,0,OS),BOOST_PP_TUPLE_ELEM(2,0,OS)(D,X,BOOST_PP_TUPLE_ELEM(2,1,OS)))
  91 #define BOOST_PP_LIST_FOLD_RIGHT_O2(D,OS,X) (BOOST_PP_TUPLE_ELEM(2,0,OS),BOOST_PP_TUPLE_ELEM(2,0,OS)(D,X,BOOST_PP_TUPLE_ELEM(2,1,OS)))
  92 #define BOOST_PP_LIST_FOLD_RIGHT_O3(D,OS,X) (BOOST_PP_TUPLE_ELEM(2,0,OS),BOOST_PP_TUPLE_ELEM(2,0,OS)(D,X,BOOST_PP_TUPLE_ELEM(2,1,OS)))
  93
  94 /** <p>Obsolete, just use BOOST_PP_LIST_FOLD_RIGHT().</p> */
  95 #define BOOST_PP_LIST_FOLD_RIGHT_2ND BOOST_PP_LIST_FOLD_RIGHT
  96 /** <p>Obsolete, just use BOOST_PP_LIST_FOLD_RIGHT_D().</p> */
  97 #define BOOST_PP_LIST_FOLD_RIGHT_2ND_D BOOST_PP_LIST_FOLD_RIGHT_D
  98 #endif