Ticket #2297: template_arity.patch

template_arity.hpp

@@ -64 +64 @@
 namespace boost { namespace mpl { namespace aux {
 
 template< BOOST_MPL_AUX_NTTP_DECL(int, N) > struct arity_tag
+  : arity_tag<N-1>
 {
-    typedef char (&type)[N + 1];
+    typedef char (&type)[N + 2];
 };
 
-#   define AUX778076_MAX_ARITY_OP(unused, state, i_) \
-    ( BOOST_PP_CAT(C,i_) > 0 ? BOOST_PP_CAT(C,i_) : state ) \
-/**/
-
-template<
-      BOOST_MPL_PP_PARAMS(AUX778076_ARITY, BOOST_MPL_AUX_NTTP_DECL(int, C))
-    >
-struct max_arity
+template <>
+struct arity_tag<0>
 {
-    BOOST_STATIC_CONSTANT(int, value = 
-          BOOST_PP_SEQ_FOLD_LEFT(
-              AUX778076_MAX_ARITY_OP
-            , -1
-            , BOOST_MPL_PP_RANGE(1, AUX778076_ARITY)
-            )
-        );
+    typedef char type;
 };
 
-#   undef AUX778076_MAX_ARITY_OP
-
 arity_tag<0>::type arity_helper(...);
 
 #   define BOOST_PP_ITERATION_LIMITS (1, AUX778076_ARITY)
 #   define BOOST_PP_FILENAME_1 <boost/mpl/aux_/template_arity.hpp>
 #   include BOOST_PP_ITERATE()
 
-template< typename F, BOOST_MPL_AUX_NTTP_DECL(int, N) >
-struct template_arity_impl
-{
-    BOOST_STATIC_CONSTANT(int, value = 
-          sizeof(arity_helper(type_wrapper<F>(),arity_tag<N>())) - 1
-        );
-};
-
-#   define AUX778076_TEMPLATE_ARITY_IMPL_INVOCATION(unused, i_, F) \
-    BOOST_PP_COMMA_IF(i_) template_arity_impl<F,BOOST_PP_INC(i_)>::value \
-/**/
-
 template< typename F >
 struct template_arity
+  : mpl::int_<
+        (sizeof(arity_helper(type_wrapper<F>(), arity_tag<AUX778076_ARITY>())) - 2)
+    >
 {
-    BOOST_STATIC_CONSTANT(int, value = (
-          max_arity< BOOST_MPL_PP_REPEAT(
-              AUX778076_ARITY
-            , AUX778076_TEMPLATE_ARITY_IMPL_INVOCATION
-            , F
-            ) >::value
-        ));
-        
-    typedef mpl::int_<value> type;
 };
 
 #   undef AUX778076_TEMPLATE_ARITY_IMPL_INVOCATION