Working on docs.

[SVN r12587]

example/count_down.c

@@ -0,0 +1,30 @@
+/* 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 is a trivial example of using BOOST_PP_WHILE() that simply
+ * counts down from N to 0 ultimately expanding to a 0.
+ */
+
+#include <boost/preprocessor/dec.hpp>
+#include <boost/preprocessor/while.hpp>
+
+#define COUNT_DOWN(N) BOOST_PP_WHILE(COUNT_DOWN_C,COUNT_DOWN_F,N)
+/* Above is the macro we are implementing using BOOST_PP_WHILE(). */
+
+#define COUNT_DOWN_C(D,N) N
+/* Above is the condition. It expands to the current N. */
+
+#define COUNT_DOWN_F(D,N) BOOST_PP_DEC(N)
+/* Above is the iteration macro. It decrements N. */
+
+enum { x = COUNT_DOWN(50) };
+/* The above expands to 0. */