From 06739046e07d670444e97bd9e9c27554db6e9d24 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Fri, 11 Mar 2016 19:15:20 +1100
Subject: [PATCH] preprocessor: add variadic MAP macro

---
 preprocessor.hpp | 54 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 51 insertions(+), 3 deletions(-)

diff --git a/preprocessor.hpp b/preprocessor.hpp
index 34a47395..04ceb3db 100644
--- a/preprocessor.hpp
+++ b/preprocessor.hpp
@@ -11,16 +11,64 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
- * Copyright 2012 Danny Robson <danny@nerdcruft.net>
+ * Copyright 2012-2016 Danny Robson <danny@nerdcruft.net>
  */
 
 #ifndef __UTIL_PREPROCESSOR_HPP
 #define __UTIL_PREPROCESSOR_HPP
 
+
 #define PASTE_DETAIL(x, y) x##y
 #define PASTE(x, y) PASTE_DETAIL(x, y)
 
-#define STRINGIFY_DETAIL(x) #x
-#define STRINGIFY(x) STRINGIFY_DETAIL(x)
+#define STRINGIZE_DETAIL(x) #x
+#define STRINGIZE(x) STRINGIZE_DETAIL(x)
+
+#define STRINGIZE_LIST(x) STRINGIZE(x),
+
+
+///////////////////////////////////////////////////////////////////////////////
+// Varags functional style map
+//
+// Based off a technique seen on StackOverflow:
+// http://stackoverflow.com/questions/11761703/overloading-macro-on-number-of-arguments
+#define MAP_01(F, X)      F(X)
+#define MAP_02(F, X, ...) F(X)MAP_01(F, __VA_ARGS__)
+#define MAP_03(F, X, ...) F(X)MAP_02(F, __VA_ARGS__)
+#define MAP_04(F, X, ...) F(X)MAP_03(F, __VA_ARGS__)
+#define MAP_05(F, X, ...) F(X)MAP_04(F, __VA_ARGS__)
+#define MAP_06(F, X, ...) F(X)MAP_05(F, __VA_ARGS__)
+#define MAP_07(F, X, ...) F(X)MAP_06(F, __VA_ARGS__)
+#define MAP_08(F, X, ...) F(X)MAP_07(F, __VA_ARGS__)
+#define MAP_09(F, X, ...) F(X)MAP_08(F, __VA_ARGS__)
+#define MAP_10(F, X, ...) F(X)MAP_09(F, __VA_ARGS__)
+#define MAP_11(F, X, ...) F(X)MAP_10(F, __VA_ARGS__)
+#define MAP_12(F, X, ...) F(X)MAP_11(F, __VA_ARGS__)
+#define MAP_13(F, X, ...) F(X)MAP_12(F, __VA_ARGS__)
+#define MAP_14(F, X, ...) F(X)MAP_13(F, __VA_ARGS__)
+#define MAP_15(F, X, ...) F(X)MAP_14(F, __VA_ARGS__)
+#define MAP_16(F, X, ...) F(X)MAP_15(F, __VA_ARGS__)
+
+
+// Uses the sliding pairs dispatch technique: by passing __VA_ARGS__ as the
+// first set of variables and appending (reverse orderred) names of the
+// corresponding macros, we get the name of the correct arity macro.
+#define ARITY_DISPATCH(                 \
+    _01,_02,_03,_04,_05,_06,_07,_08,    \
+    _09,_10,_11,_12,_13,_14,_15,_16,    \
+    NAME,...                            \
+) NAME
+
+
+// Map a macro across __VA_ARGS__. Can be easily expanded, but has non-obvious
+// failure mode when supported arity is exceeded. Don't use this, unless you
+// really need the stringize operator, or other macro magic.
+//
+// Just use C++ templates. Really...
+#define MAP(FUNC,...)                                               \
+ARITY_DISPATCH(__VA_ARGS__,                                         \
+    MAP_16, MAP_15, MAP_14, MAP_13, MAP_12, MAP_11, MAP_10, MAP_09, \
+    MAP_08, MAP_07, MAP_06, MAP_05, MAP_04, MAP_03, MAP_02, MAP_01  \
+)(FUNC, __VA_ARGS__)
 
 #endif