Add syntactic sugar to Eigen tensors to allow more natural syntax.

Specifically, this enables expressions involving:

scalar + tensor
scalar * tensor
scalar / tensor
scalar - tensor

1 files changed, 30 insertions, 0 deletions

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h b/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h
index 1eaa8d4fc..12f8a1499 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h
@@ -216,6 +216,13 @@ class TensorBase<Derived, ReadOnlyAccessors>
     }
 
     EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE friend
+    const TensorCwiseUnaryOp<internal::scalar_add_op<Scalar>, const Derived>
+    operator+ (Scalar lhs, const Derived& rhs) {
+      return rhs + lhs;
+    }
+
+    EIGEN_DEVICE_FUNC
     EIGEN_STRONG_INLINE const TensorCwiseUnaryOp<internal::scalar_sub_op<Scalar>, const Derived>
     operator- (Scalar rhs) const {
       EIGEN_STATIC_ASSERT((NumTraits<Scalar>::IsSigned || internal::is_same<Scalar, const std::complex<float> >::value), YOU_MADE_A_PROGRAMMING_MISTAKE);
@@ -223,18 +230,41 @@ class TensorBase<Derived, ReadOnlyAccessors>
     }
 
     EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE friend
+    const TensorCwiseUnaryOp<internal::scalar_add_op<Scalar>,
+                             const TensorCwiseUnaryOp<internal::scalar_opposite_op<Scalar>, const Derived> >
+    operator- (Scalar lhs, const Derived& rhs) {
+      return -rhs + lhs;
+    }
+
+    EIGEN_DEVICE_FUNC
     EIGEN_STRONG_INLINE const TensorCwiseUnaryOp<internal::scalar_multiple_op<Scalar>, const Derived>
     operator* (Scalar rhs) const {
       return unaryExpr(internal::scalar_multiple_op<Scalar>(rhs));
     }
 
     EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE friend
+    const TensorCwiseUnaryOp<internal::scalar_multiple_op<Scalar>, const Derived>
+    operator* (Scalar lhs, const Derived& rhs) {
+      return rhs * lhs;
+    }
+
+    EIGEN_DEVICE_FUNC
     EIGEN_STRONG_INLINE const TensorCwiseUnaryOp<internal::scalar_quotient1_op<Scalar>, const Derived>
     operator/ (Scalar rhs) const {
       return unaryExpr(internal::scalar_quotient1_op<Scalar>(rhs));
     }
 
     EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE friend
+    const TensorCwiseUnaryOp<internal::scalar_multiple_op<Scalar>,
+                             const TensorCwiseUnaryOp<internal::scalar_inverse_op<Scalar>, const Derived> >
+    operator/ (Scalar lhs, const Derived& rhs) {
+      return rhs.inverse() * lhs;
+    }
+
+    EIGEN_DEVICE_FUNC
     EIGEN_STRONG_INLINE const TensorCwiseUnaryOp<internal::scalar_mod_op<Scalar>, const Derived>
     operator% (Scalar rhs) const {
       EIGEN_STATIC_ASSERT(NumTraits<Scalar>::IsInteger, YOU_MADE_A_PROGRAMMING_MISTAKE_TRY_MOD);