From abd1c1af7a568b067ca8cec8b8345a7a6f9d2c28 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Fri, 20 May 2016 15:01:27 +0200
Subject: [PATCH] Make EIGEN_HAS_STD_RESULT_OF user configurable

---
 Eigen/src/Core/util/Macros.h | 4 ++++
 Eigen/src/Core/util/Meta.h   | 2 +-
 test/mixingtypes.cpp         | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Eigen/src/Core/util/Macros.h b/Eigen/src/Core/util/Macros.h
index 3fcef82b6..fe383ee9a 100644
--- a/Eigen/src/Core/util/Macros.h
+++ b/Eigen/src/Core/util/Macros.h
@@ -372,8 +372,12 @@
 #endif
 
 // Does the compiler support result_of?
+#ifndef EIGEN_HAS_STD_RESULT_OF
 #if EIGEN_MAX_CPP_VER>=11 && ((__has_feature(cxx_lambdas) || (defined(__cplusplus) && __cplusplus >= 201103L)))
 #define EIGEN_HAS_STD_RESULT_OF 1
+#else
+#define EIGEN_HAS_STD_RESULT_OF 0
+#endif
 #endif
 
 // Does the compiler support variadic templates?
diff --git a/Eigen/src/Core/util/Meta.h b/Eigen/src/Core/util/Meta.h
index 24e8a6d8a..1212f0cd3 100644
--- a/Eigen/src/Core/util/Meta.h
+++ b/Eigen/src/Core/util/Meta.h
@@ -254,7 +254,7 @@ protected:
   * upcoming next STL generation (using a templated result member).
   * If none of these members is provided, then the type of the first argument is returned. FIXME, that behavior is a pretty bad hack.
   */
-#ifdef EIGEN_HAS_STD_RESULT_OF
+#if EIGEN_HAS_STD_RESULT_OF
 template<typename T> struct result_of {
   typedef typename std::result_of<T>::type type1;
   typedef typename remove_all<type1>::type type;
diff --git a/test/mixingtypes.cpp b/test/mixingtypes.cpp
index 3d0875481..dbcf468ea 100644
--- a/test/mixingtypes.cpp
+++ b/test/mixingtypes.cpp
@@ -57,7 +57,7 @@ template<int SizeAtCompileType> void mixingtypes(int size = SizeAtCompileType)
 
   mf+mf;
   VERIFY_RAISES_ASSERT(mf+md);
-#ifndef EIGEN_HAS_STD_RESULT_OF
+#if !EIGEN_HAS_STD_RESULT_OF
   // this one does not even compile with C++11
   VERIFY_RAISES_ASSERT(mf+mcf);
 #endif