From 923ba6b7453203a4d604ce44b5d2a2828a2c90ea Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Sat, 3 Mar 2018 13:41:35 +1100
Subject: [PATCH] types/traits: add dedicated function argument counting trait

---
 types/traits.hpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/types/traits.hpp b/types/traits.hpp
index 265521c2..73e20c24 100644
--- a/types/traits.hpp
+++ b/types/traits.hpp
@@ -257,6 +257,21 @@ struct func_traits : public ::detail::func_traits<
 };
 
 
+///////////////////////////////////////////////////////////////////////////////
+template <typename FunctionT>
+struct function_argument_count : public std::integral_constant<
+    size_t,
+    std::tuple_size_v<
+        typename func_traits<FunctionT>::argument_types
+    >
+> { };
+
+
+//-----------------------------------------------------------------------------
+template <typename FunctionT>
+constexpr auto function_argument_count_v = function_argument_count<FunctionT>::value;
+
+
 
 ///////////////////////////////////////////////////////////////////////////////
 template <std::size_t N, typename FuncT>