From 829dddd0fdb1bfd4942ff35fe7dfd4ccdeddc97e Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Thu, 19 Feb 2015 15:18:37 +0100
Subject: [PATCH] Add support for C++11 result_of/lambdas

---
 Eigen/src/Core/util/Macros.h |  5 +++++
 Eigen/src/Core/util/Meta.h   | 32 ++++++++++++++++++++++++++------
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/Eigen/src/Core/util/Macros.h b/Eigen/src/Core/util/Macros.h
index e607cdd12..aaea9f035 100644
--- a/Eigen/src/Core/util/Macros.h
+++ b/Eigen/src/Core/util/Macros.h
@@ -382,6 +382,11 @@
   #define EIGEN_HAVE_RVALUE_REFERENCES
 #endif
 
+// Does the compiler support result_of?
+#if (__has_feature(cxx_lambdas) || (defined(__cplusplus) && __cplusplus >= 201103L))
+#define EIGEN_HAS_STD_RESULT_OF 1
+#endif
+
 // Does the compiler support variadic templates?
 #if __cplusplus > 199711L
 #define EIGEN_HAS_VARIADIC_TEMPLATES 1
diff --git a/Eigen/src/Core/util/Meta.h b/Eigen/src/Core/util/Meta.h
index 3be9e6ca5..674cd8f97 100644
--- a/Eigen/src/Core/util/Meta.h
+++ b/Eigen/src/Core/util/Meta.h
@@ -165,6 +165,7 @@ template<typename T> struct result_of {};
 struct has_none {int a[1];};
 struct has_std_result_type {int a[2];};
 struct has_tr1_result {int a[3];};
+struct has_cxx_eleven_result {int a[4];};
 
 template<typename Func, typename ArgType, int SizeOf=sizeof(has_none)>
 struct unary_result_of_select {typedef ArgType type;};
@@ -175,13 +176,22 @@ struct unary_result_of_select<Func, ArgType, sizeof(has_std_result_type)> {typed
 template<typename Func, typename ArgType>
 struct unary_result_of_select<Func, ArgType, sizeof(has_tr1_result)> {typedef typename Func::template result<Func(ArgType)>::type type;};
 
+#ifdef EIGEN_HAS_STD_RESULT_OF
+template<typename Func, typename ArgType>
+struct unary_result_of_select<Func, ArgType, sizeof(has_cxx_eleven_result)> {typedef typename std::result_of<Func(ArgType)>::type type;};
+#endif
+
 template<typename Func, typename ArgType>
 struct result_of<Func(ArgType)> {
     template<typename T>
-    static has_std_result_type testFunctor(T const *, typename T::result_type const * = 0);
+    static has_std_result_type    testFunctor(T const *, typename T::result_type const * = 0);
     template<typename T>
-    static has_tr1_result      testFunctor(T const *, typename T::template result<T(ArgType)>::type const * = 0);
-    static has_none            testFunctor(...);
+    static has_tr1_result         testFunctor(T const *, typename T::template result<T(ArgType)>::type const * = 0);
+#ifdef EIGEN_HAS_STD_RESULT_OF
+    template<typename T>
+    static has_cxx_eleven_result  testFunctor(T const *, typename std::result_of<T(ArgType)>::type const * = 0);
+#endif
+    static has_none               testFunctor(...);
 
     // note that the following indirection is needed for gcc-3.3
     enum {FunctorType = sizeof(testFunctor(static_cast<Func*>(0)))};
@@ -199,13 +209,23 @@ template<typename Func, typename ArgType0, typename ArgType1>
 struct binary_result_of_select<Func, ArgType0, ArgType1, sizeof(has_tr1_result)>
 {typedef typename Func::template result<Func(ArgType0,ArgType1)>::type type;};
 
+#ifdef EIGEN_HAS_STD_RESULT_OF
+template<typename Func, typename ArgType0, typename ArgType1>
+struct binary_result_of_select<Func, ArgType0, ArgType1, sizeof(has_cxx_eleven_result)>
+{typedef typename std::result_of<Func(ArgType0, ArgType1)>::type type;};
+#endif
+
 template<typename Func, typename ArgType0, typename ArgType1>
 struct result_of<Func(ArgType0,ArgType1)> {
     template<typename T>
-    static has_std_result_type testFunctor(T const *, typename T::result_type const * = 0);
+    static has_std_result_type    testFunctor(T const *, typename T::result_type const * = 0);
     template<typename T>
-    static has_tr1_result      testFunctor(T const *, typename T::template result<T(ArgType0,ArgType1)>::type const * = 0);
-    static has_none            testFunctor(...);
+    static has_tr1_result         testFunctor(T const *, typename T::template result<T(ArgType0,ArgType1)>::type const * = 0);
+#ifdef EIGEN_HAS_STD_RESULT_OF
+    template<typename T>
+    static has_cxx_eleven_result  testFunctor(T const *, typename std::result_of<T(ArgType0, ArgType1)>::type const * = 0);
+#endif
+    static has_none               testFunctor(...);
 
     // note that the following indirection is needed for gcc-3.3
     enum {FunctorType = sizeof(testFunctor(static_cast<Func*>(0)))};