使用boost的preprocessor

使用boost的preprocessor

在线文档：http://www.boost.org/doc/libs/1_48_0/libs/preprocessor/doc/index.html
              http://www.boost.org/doc/libs/1_48_0/libs/preprocessor/doc/topics/techniques.html
              http://www.boost.org/doc/libs/1_48_0/libs/preprocessor/doc/ref.html
几篇不错的博文：http://blog.csdn.net/zx77/article/details/2270991
一个关于2D的repeat的实现 ：
/* Copyright (C) 2002
 * Housemarque Oy
 * http://www.housemarque.com
 *
 * Permission to copy, use, modify, sell and distribute this software is
 * granted provided this copyright notice appears in all copies. This
 * software is provided "as is" without express or implied warranty, and
 * with no claim as to its suitability for any purpose.
 *
 * See http://www.boost.org for most recent version.
 */

/* This example implements a generalized macro for 2D repetition using
 * the simple repetition primitives of the preprocessor library.
 */

#include "preprocessor/repeat.hpp"
#include "preprocessor/logical/or.hpp"
#include "preprocessor/comma_if.hpp"
#include "preprocessor/list/cat.hpp"
#include "preprocessor/tuple/elem.hpp"
#include "preprocessor/tuple/to_list.hpp"

/** <p>Repeats the macro <code>M(X,Y,DATA)</code> for <code>X = [0,W)</code> and <code>Y = [0,H)</code>.</p>

<p>In other words, expands to the sequence:</p>

<pre>
M(  0,  0,  DATA) M(  1,  0,  DATA) ... M(W-1,  0,  DATA)
M(  0,  1,  DATA) M(  1,  1,  DATA) ... M(W-1,  1,  DATA)
      ...            ...      ...       ...
M(  0,H-1,  DATA) M(  1,H-1,  DATA) ... M(W-1,H-1,  DATA)
</pre>
*/
#define REPEAT_2D(W,H,M,DATA)\
  /* Here we can simply use BOOST_PP_REPEAT(), because\
   * it implements automatic recursion.\
   */\
  BOOST_PP_REPEAT\
  ( H\
  , REPEAT_2D_ROW\
  , (W,M,DATA)\
  )
#define REPEAT_2D_ROW(z,Y,WMD)\
  BOOST_PP_REPEAT\
  ( BOOST_PP_TUPLE_ELEM(3,0,WMD)\
  , REPEAT_2D_ELEM\
  , (Y, BOOST_PP_TUPLE_ELEM(3,1,WMD), BOOST_PP_TUPLE_ELEM(3,2,WMD))\
  )
#define REPEAT_2D_ELEM(z,X,YMD)\
  BOOST_PP_TUPLE_ELEM(3,1,YMD)\
  ( X\
  , BOOST_PP_TUPLE_ELEM(3,0,YMD)\
  , BOOST_PP_TUPLE_ELEM(3,2,YMD)\
  )

/* Here we use the above macro to generate something. */
#define ELEM(X,Y,E) BOOST_PP_COMMA_IF(BOOST_PP_OR(X,Y)) BOOST_PP_LIST_CAT(BOOST_PP_TUPLE_TO_LIST(5,(E,_,X,_,Y)))
enum { REPEAT_2D(3,4,ELEM,elem) };

/* The above expands to:
 *
 * enum { elem_0_0, elem_1_0, elem_2_0,
 *        elem_0_1, elem_1_1, elem_2_1,
 *        elem_0_2, elem_1_2, elem_2_2,
 *        elem_0_3, elem_1_3, elem_2_3 };
 */