From 6761c64d60f297d429a502dbf064b36b6dfb6c9b Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Thu, 19 May 2016 18:34:16 +0200
Subject: zeta and polygamma are not unary functions, but binary ones.

---
 Eigen/src/Core/GlobalFunctions.h | 38 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

(limited to 'Eigen/src/Core/GlobalFunctions.h')

diff --git a/Eigen/src/Core/GlobalFunctions.h b/Eigen/src/Core/GlobalFunctions.h
index 05ba6ddb4..2173e026d 100644
--- a/Eigen/src/Core/GlobalFunctions.h
+++ b/Eigen/src/Core/GlobalFunctions.h
@@ -51,8 +51,6 @@ namespace Eigen
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(tanh,scalar_tanh_op)
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(lgamma,scalar_lgamma_op)
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(digamma,scalar_digamma_op)
-  EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(zeta,scalar_zeta_op)
-  EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(polygamma,scalar_polygamma_op)
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(erf,scalar_erf_op)
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(erfc,scalar_erfc_op)
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(exp,scalar_exp_op)
@@ -161,6 +159,42 @@ namespace Eigen
     );
   }
 
+  /** \cpp11 \returns an expression of the coefficient-wise polygamma(\a n, \a x) to the given arrays.
+    *
+    * It returns the \a n -th derivative of the digamma(psi) evaluated at \c x.
+    *
+    */
+  // * \warning Be careful with the order of the parameters: x.polygamma(n) is equivalent to polygamma(n,x)
+  // * \sa ArrayBase::polygamma()
+  template<typename DerivedN,typename DerivedX>
+  inline const Eigen::CwiseBinaryOp<Eigen::internal::scalar_polygamma_op<typename DerivedX::Scalar>, const DerivedN, const DerivedX>
+  polygamma(const Eigen::ArrayBase<DerivedN>& n, const Eigen::ArrayBase<DerivedX>& x)
+  {
+    return Eigen::CwiseBinaryOp<Eigen::internal::scalar_polygamma_op<typename DerivedX::Scalar>, const DerivedN, const DerivedX>(
+      n.derived(),
+      x.derived()
+    );
+  }
+
+  /** \returns an expression of the coefficient-wise zeta(\a x, \a q) to the given arrays.
+    *
+    * It returns the Riemann zeta function of two arguments \a x and \a q:
+    *
+    * \param x is the exposent, it must be > 1
+    * \param q is the shift, it must be > 0
+    *
+    * \sa ArrayBase::zeta()
+    */
+  template<typename DerivedX,typename DerivedQ>
+  inline const Eigen::CwiseBinaryOp<Eigen::internal::scalar_zeta_op<typename DerivedX::Scalar>, const DerivedX, const DerivedQ>
+  zeta(const Eigen::ArrayBase<DerivedX>& x, const Eigen::ArrayBase<DerivedQ>& q)
+  {
+    return Eigen::CwiseBinaryOp<Eigen::internal::scalar_zeta_op<typename DerivedX::Scalar>, const DerivedX, const DerivedQ>(
+      x.derived(),
+      q.derived()
+    );
+  }
+
   namespace internal
   {
     EIGEN_ARRAY_DECLARE_GLOBAL_EIGEN_UNARY(real,scalar_real_op)
-- 
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