add EqualSpaced / setEqualSpaced

Eigen/src/Core/CwiseNullaryOp.h

diff --git a/Eigen/src/Core/CwiseNullaryOp.h b/Eigen/src/Core/CwiseNullaryOp.h
index a62f54d..b33c052 100644
--- a/Eigen/src/Core/CwiseNullaryOp.h
+++ b/Eigen/src/Core/CwiseNullaryOp.h
@@ -306,6 +306,20 @@
   return DenseBase<Derived>::NullaryExpr(Derived::SizeAtCompileTime, internal::linspaced_op<Scalar>(low,high,Derived::SizeAtCompileTime));
 }
 
+template <typename Derived>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const typename DenseBase<Derived>::RandomAccessEqualSpacedReturnType
+DenseBase<Derived>::EqualSpaced(Index size, const Scalar& low, const Scalar& step) {
+  EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived)
+  return DenseBase<Derived>::NullaryExpr(size, internal::equalspaced_op<Scalar>(low, step));
+}
+
+template <typename Derived>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const typename DenseBase<Derived>::RandomAccessEqualSpacedReturnType
+DenseBase<Derived>::EqualSpaced(const Scalar& low, const Scalar& step) {
+  EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived)
+  return DenseBase<Derived>::NullaryExpr(Derived::SizeAtCompileTime, internal::equalspaced_op<Scalar>(low, step));
+}
+
 /** \returns true if all coefficients in this matrix are approximately equal to \a val, to within precision \a prec */
 template<typename Derived>
 EIGEN_DEVICE_FUNC bool DenseBase<Derived>::isApproxToConstant
@@ -455,6 +469,19 @@
   return setLinSpaced(size(), low, high);
 }
 
+template <typename Derived>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Derived& DenseBase<Derived>::setEqualSpaced(Index newSize, const Scalar& low,
+                                                                                  const Scalar& step) {
+  EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived)
+  return derived() = Derived::NullaryExpr(newSize, internal::equalspaced_op<Scalar>(low, step));
+}
+template <typename Derived>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Derived& DenseBase<Derived>::setEqualSpaced(const Scalar& low,
+                                                                                  const Scalar& step) {
+  EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived)
+  return setEqualSpaced(size(), low, step);
+}
+
 // zero:
 
 /** \returns an expression of a zero matrix.

Eigen/src/Core/DenseBase.h

diff --git a/Eigen/src/Core/DenseBase.h b/Eigen/src/Core/DenseBase.h
index 6e17779..24dc697 100644
--- a/Eigen/src/Core/DenseBase.h
+++ b/Eigen/src/Core/DenseBase.h
@@ -258,6 +258,8 @@
     EIGEN_DEPRECATED typedef CwiseNullaryOp<internal::linspaced_op<Scalar>,PlainObject> SequentialLinSpacedReturnType;
     /** \internal Represents a vector with linearly spaced coefficients that allows random access. */
     typedef CwiseNullaryOp<internal::linspaced_op<Scalar>,PlainObject> RandomAccessLinSpacedReturnType;
+    /** \internal Represents a vector with equally spaced coefficients that allows random access. */
+    typedef CwiseNullaryOp<internal::equalspaced_op<Scalar>, PlainObject> RandomAccessEqualSpacedReturnType;
     /** \internal the return type of MatrixBase::eigenvalues() */
     typedef Matrix<typename NumTraits<typename internal::traits<Derived>::Scalar>::Real, internal::traits<Derived>::ColsAtCompileTime, 1> EigenvaluesReturnType;
 
@@ -336,6 +338,11 @@
     EIGEN_DEVICE_FUNC static const RandomAccessLinSpacedReturnType
     LinSpaced(const Scalar& low, const Scalar& high);
 
+    EIGEN_DEVICE_FUNC static const RandomAccessEqualSpacedReturnType
+    EqualSpaced(Index size, const Scalar& low, const Scalar& step);
+    EIGEN_DEVICE_FUNC static const RandomAccessEqualSpacedReturnType
+    EqualSpaced(const Scalar& low, const Scalar& step);
+
     template<typename CustomNullaryOp> EIGEN_DEVICE_FUNC
     static const CwiseNullaryOp<CustomNullaryOp, PlainObject>
     NullaryExpr(Index rows, Index cols, const CustomNullaryOp& func);
@@ -357,6 +364,8 @@
     EIGEN_DEVICE_FUNC Derived& setConstant(const Scalar& value);
     EIGEN_DEVICE_FUNC Derived& setLinSpaced(Index size, const Scalar& low, const Scalar& high);
     EIGEN_DEVICE_FUNC Derived& setLinSpaced(const Scalar& low, const Scalar& high);
+    EIGEN_DEVICE_FUNC Derived& setEqualSpaced(Index size, const Scalar& low, const Scalar& step);
+    EIGEN_DEVICE_FUNC Derived& setEqualSpaced(const Scalar& low, const Scalar& step);
     EIGEN_DEVICE_FUNC Derived& setZero();
     EIGEN_DEVICE_FUNC Derived& setOnes();
     EIGEN_DEVICE_FUNC Derived& setRandom();

Eigen/src/Core/functors/NullaryFunctors.h

diff --git a/Eigen/src/Core/functors/NullaryFunctors.h b/Eigen/src/Core/functors/NullaryFunctors.h
index e099d4a..f18974b 100644
--- a/Eigen/src/Core/functors/NullaryFunctors.h
+++ b/Eigen/src/Core/functors/NullaryFunctors.h
@@ -145,6 +145,39 @@
   const linspaced_op_impl<Scalar,NumTraits<Scalar>::IsInteger> impl;
 };
 
+template <typename Scalar>
+struct equalspaced_op {
+  typedef typename NumTraits<Scalar>::Real RealScalar;
+
+  EIGEN_DEVICE_FUNC equalspaced_op(const Scalar& start, const Scalar& step) : m_start(start), m_step(step) {}
+  template <typename IndexType>
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Scalar operator()(IndexType i) const {
+    return m_start + m_step * static_cast<Scalar>(i);
+  }
+  template <typename Packet, typename IndexType>
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet packetOp(IndexType i) const {
+    const Packet cst_start = pset1<Packet>(m_start);
+    const Packet cst_step = pset1<Packet>(m_step);
+    const Packet cst_lin0 = plset<Packet>(Scalar(0));
+    const Packet cst_offset = pmadd(cst_lin0, cst_step, cst_start);
+
+    Packet istep = pset1<Packet>(static_cast<Scalar>(i) * m_step);
+    return padd(cst_offset, istep);
+  }
+  const Scalar m_start;
+  const Scalar m_step;
+};
+
+template <typename Scalar>
+struct functor_traits<equalspaced_op<Scalar> > {
+  enum {
+    Cost = NumTraits<Scalar>::AddCost + NumTraits<Scalar>::MulCost,
+    PacketAccess =
+        packet_traits<Scalar>::HasSetLinear && packet_traits<Scalar>::HasMul && packet_traits<Scalar>::HasAdd,
+    IsRepeatable = true
+  };
+};
+
 // Linear access is automatically determined from the operator() prototypes available for the given functor.
 // If it exposes an operator()(i,j), then we assume the i and j coefficients are required independently
 // and linear access is not possible. In all other cases, linear access is enabled.

test/nullary.cpp

diff --git a/test/nullary.cpp b/test/nullary.cpp
index 2c4d938..e524837 100644
--- a/test/nullary.cpp
+++ b/test/nullary.cpp
@@ -78,8 +78,9 @@
   const Scalar step = ((size == 1) ? 1 : (high-low)/RealScalar(size-1));
 
   // check whether the result yields what we expect it to do
-  VectorType m(base);
+  VectorType m(base), o(base);
   m.setLinSpaced(size,low,high);
+  o.setEqualSpaced(size, low, step);
 
   if(!NumTraits<Scalar>::IsInteger)
   {
@@ -87,6 +88,7 @@
     for (int i=0; i<size; ++i)
       n(i) = low+RealScalar(i)*step;
     VERIFY_IS_APPROX(m,n);
+    VERIFY_IS_APPROX(n,o);
 
     CALL_SUBTEST( check_extremity_accuracy(m, low, high) );
   }
@@ -256,11 +258,12 @@
 {
   // Check possible overflow issue
   int n = 60000;
-  ArrayXi a1(n), a2(n);
-  a1.setLinSpaced(n, 0, n-1);
-  for(int i=0; i<n; ++i)
-    a2(i) = i;
-  VERIFY_IS_APPROX(a1,a2);
+  ArrayXi a1(n), a2(n), a_ref(n);
+  a1.setLinSpaced(n, 0, n - 1);
+  a2.setEqualSpaced(n, 0, 1);
+  for (int i = 0; i < n; ++i) a_ref(i) = i;
+  VERIFY_IS_APPROX(a1, a_ref);
+  VERIFY_IS_APPROX(a2, a_ref);
 }
 
 template<int>