Added list data structure

[SVN r12433]

doc/reference/repeat_8hpp.html

@@ -55,7 +55,59 @@ In other words, expands to the sequence:
   M(0,P) M(1,P) ... M(N-1,P)
 </pre></div></pre>
 <p>
-See BOOST_PP_LIMIT_MAG.     </td>
+See BOOST_PP_LIMIT_MAG.
+<p>
+<h3>2D and 3D repetition</h3>
+
+<p>
+2D and 3D repetition are supported with the <a class="el" href="repeat__2nd_8hpp.html#a0">BOOST_PP_REPEAT_2ND</a>() and <a class="el" href="repeat__3rd_8hpp.html#a0">BOOST_PP_REPEAT_3RD</a>() macros. For example,
+<p>
+<pre><div class="fragment"><pre>
+  // A generalized macro for generating 2D arrays
+  #define ARRAY_2D(W,H,M,P)\
+    BOOST_PP_REPEAT_2ND\
+    ( H\
+    , ARRAY_2D_ROW\
+    , (W,H,M,P)\
+    )
+  #define ARRAY_2D_ROW(Y,WHMP)\
+    BOOST_PP_EXPAND\
+    ( BOOST_PP_REPEAT\
+      ( BOOST_PP_TUPLE_ELEM(4,0,WHMP)\
+      , ARRAY_2D_ELEM\
+      , (Y,BOOST_PP_TUPLE4_ENUM WHMP)\
+      )\
+    )
+  #define BOOST_PP_TUPLE4_ENUM(A,B,C,D) A,B,C,D
+  #define ARRAY_2D_ELEM(X,YWHMP)\
+    BOOST_PP_TUPLE_ELEM(5,3,YWHMP)\
+    BOOST_PP_EXPAND\
+    ( ( X\
+      , BOOST_PP_TUPLE_ELEM(5,0,YWHMP)\
+      , BOOST_PP_TUPLE_ELEM(5,1,YWHMP)\
+      , BOOST_PP_TUPLE_ELEM(5,2,YWHMP)\
+      , BOOST_PP_TUPLE_ELEM(5,4,YWHMP)\
+      )\
+    )
+
+  // Here we use the above macro to generate something
+  #define ELEM(X,Y,W,H,E) BOOST_PP_COMMA_IF(BOOST_PP_OR(X,Y)) E##_##X##_##Y
+
+  ARRAY_2D(3,4,ELEM,elem)
+</pre></div></pre>
+<p>
+expands to:
+<p>
+<pre><div class="fragment"><pre>
+  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
+</pre></div></pre>
+<p>
+Since recursive expansion of macros is not allowed by the C++ preprocessor, replacing the BOOST_PP_REPEAT_2ND above with BOOST_PP_REPEAT, would not produce the above expansion.
+<p>
+See <a class="el" href="for_8hpp.html#a0">BOOST_PP_FOR</a>().     </td>
   </tr>
 </table>
 <a name="a1" doxytag="repeat.hpp::BOOST_PREPROCESSOR_REPEAT"></a><p>