From b178cc347968675bdae942dbdcb7de9ed9daa564 Mon Sep 17 00:00:00 2001
From: Benoit Steiner <benoit.steiner.goog@gmail.com>
Date: Wed, 21 Oct 2015 11:28:28 -0700
Subject: Added some syntactic sugar to make it simpler to compare a tensor to
 a scalar.

---
 unsupported/Eigen/CXX11/src/Tensor/TensorBase.h | 32 +++++++++++++++++++++
 unsupported/test/CMakeLists.txt                 |  1 +
 unsupported/test/cxx11_tensor_sugar.cpp         | 38 +++++++++++++++++++++++++
 3 files changed, 71 insertions(+)
 create mode 100644 unsupported/test/cxx11_tensor_sugar.cpp

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h b/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h
index c00f67950..1b85f5ef5 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h
@@ -279,6 +279,38 @@ class TensorBase<Derived, ReadOnlyAccessors>
       return binaryExpr(other.derived(), std::not_equal_to<Scalar>());
     }
 
+    // comparisons and tests for Scalars
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const TensorCwiseBinaryOp<std::less<Scalar>, const Derived, const TensorCwiseNullaryOp<internal::scalar_constant_op<Scalar>, const Derived> >
+    operator<(Scalar threshold) const {
+      return operator<(constant(threshold));
+    }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const TensorCwiseBinaryOp<std::less_equal<Scalar>, const Derived, const TensorCwiseNullaryOp<internal::scalar_constant_op<Scalar>, const Derived> >
+    operator<=(Scalar threshold) const {
+      return operator<=(constant(threshold));
+    }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const TensorCwiseBinaryOp<std::greater<Scalar>, const Derived, const TensorCwiseNullaryOp<internal::scalar_constant_op<Scalar>, const Derived> >
+    operator>(Scalar threshold) const {
+      return operator>(constant(threshold));
+    }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const TensorCwiseBinaryOp<std::greater_equal<Scalar>, const Derived, const TensorCwiseNullaryOp<internal::scalar_constant_op<Scalar>, const Derived> >
+    operator>=(Scalar threshold) const {
+      return operator>=(constant(threshold));
+    }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const TensorCwiseBinaryOp<std::equal_to<Scalar>, const Derived, const TensorCwiseNullaryOp<internal::scalar_constant_op<Scalar>, const Derived> >
+    operator==(Scalar threshold) const {
+      return operator==(constant(threshold));
+    }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const TensorCwiseBinaryOp<std::not_equal_to<Scalar>, const Derived, const TensorCwiseNullaryOp<internal::scalar_constant_op<Scalar>, const Derived> >
+    operator!=(Scalar threshold) const {
+      return operator!=(constant(threshold));
+    }
+
     // Coefficient-wise ternary operators.
     template<typename ThenDerived, typename ElseDerived> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
     const TensorSelectOp<const Derived, const ThenDerived, const ElseDerived>
diff --git a/unsupported/test/CMakeLists.txt b/unsupported/test/CMakeLists.txt
index 8865892e6..5a9ed5730 100644
--- a/unsupported/test/CMakeLists.txt
+++ b/unsupported/test/CMakeLists.txt
@@ -143,6 +143,7 @@ if(EIGEN_TEST_CXX11)
   ei_add_test(cxx11_tensor_generator "-std=c++0x")
   ei_add_test(cxx11_tensor_custom_op "-std=c++0x")
   ei_add_test(cxx11_tensor_custom_index "-std=c++0x")
+  ei_add_test(cxx11_tensor_sugar "-std=c++0x")
 
   # These tests needs nvcc
 #  ei_add_test(cxx11_tensor_device "-std=c++0x")
diff --git a/unsupported/test/cxx11_tensor_sugar.cpp b/unsupported/test/cxx11_tensor_sugar.cpp
new file mode 100644
index 000000000..7848acc8b
--- /dev/null
+++ b/unsupported/test/cxx11_tensor_sugar.cpp
@@ -0,0 +1,38 @@
+#include "main.h"
+
+#include <Eigen/CXX11/Tensor>
+
+using Eigen::Tensor;
+using Eigen::RowMajor;
+
+static void test_comparison_sugar() {
+  // we already trust comparisons between tensors, we're simply checking that
+  // the sugared versions are doing the same thing
+  Tensor<int, 3> t(6, 7, 5);
+
+  t.setRandom();
+  // make sure we have at least one value == 0
+  t(0,0,0) = 0;
+
+  Tensor<bool,1> b;
+
+#define TEST_TENSOR_EQUAL(e1, e2) \
+  b = ((e1) == (e2)).all();       \
+  VERIFY(b(0))
+
+#define TEST_OP(op) TEST_TENSOR_EQUAL(t op 0, t op t.constant(0))
+
+  TEST_OP(==);
+  TEST_OP(!=);
+  TEST_OP(<=);
+  TEST_OP(>=);
+  TEST_OP(<);
+  TEST_OP(>);
+#undef TEST_OP
+#undef TEST_TENSOR_EQUAL
+}
+
+void test_cxx11_tensor_sugar()
+{
+  CALL_SUBTEST(test_comparison_sugar());
+}
-- 
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