From b6b8578a678c0ebe8ed80bdd975882d37902952f Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Thu, 19 May 2016 11:36:38 +0200
Subject: [PATCH] bug #1230: add support for SelfadjointView::triangularView.

---
 Eigen/src/Core/SelfAdjointView.h | 23 +++++++++++++++++++++++
 test/triangular.cpp              |  6 ++++++
 2 files changed, 29 insertions(+)

diff --git a/Eigen/src/Core/SelfAdjointView.h b/Eigen/src/Core/SelfAdjointView.h
index 9fda02691..3a8cc221f 100644
--- a/Eigen/src/Core/SelfAdjointView.h
+++ b/Eigen/src/Core/SelfAdjointView.h
@@ -162,6 +162,29 @@ template<typename _MatrixType, unsigned int UpLo> class SelfAdjointView
     EIGEN_DEVICE_FUNC
     SelfAdjointView& rankUpdate(const MatrixBase<DerivedU>& u, const Scalar& alpha = Scalar(1));
 
+    /** \returns an expression of a triangular view extracted from the current selfadjoint view of a given triangular part
+      *
+      * The parameter \a TriMode can have the following values: \c #Upper, \c #StrictlyUpper, \c #UnitUpper,
+      * \c #Lower, \c #StrictlyLower, \c #UnitLower.
+      *
+      * If \c TriMode references the same triangular part than \c *this, then this method simply return a \c TriangularView of the nested expression,
+      * otherwise, the nested expression is first transposed, thus returning a \c TriangularView<Transpose<MatrixType>> object.
+      *
+      * \sa MatrixBase::triangularView(), class TriangularView
+      */
+    template<unsigned int TriMode>
+    EIGEN_DEVICE_FUNC
+    typename internal::conditional<(TriMode&(Upper|Lower))==(UpLo&(Upper|Lower)),
+                                   TriangularView<MatrixType,TriMode>,
+                                   TriangularView<const Transpose<MatrixType>,TriMode> >::type
+    triangularView() const
+    {
+      typename internal::conditional<(TriMode&(Upper|Lower))==(UpLo&(Upper|Lower)), MatrixType&, Transpose<MatrixType> >::type tmp(m_matrix);
+      return typename internal::conditional<(TriMode&(Upper|Lower))==(UpLo&(Upper|Lower)),
+                                   TriangularView<MatrixType,TriMode>,
+                                   TriangularView<const Transpose<MatrixType>,TriMode> >::type(tmp);
+    }
+
 /////////// Cholesky module ///////////
 
     const LLT<PlainObject, UpLo> llt() const;
diff --git a/test/triangular.cpp b/test/triangular.cpp
index 3e120f406..519916dc9 100644
--- a/test/triangular.cpp
+++ b/test/triangular.cpp
@@ -121,6 +121,12 @@ template<typename MatrixType> void triangular_square(const MatrixType& m)
   VERIFY_IS_APPROX(m1.template triangularView<Upper>() * m5, m3*m5);
   VERIFY_IS_APPROX(m6*m1.template triangularView<Upper>(), m6*m3);
 
+  m1up = m1.template triangularView<Upper>();
+  VERIFY_IS_APPROX(m1.template selfadjointView<Upper>().template triangularView<Upper>().toDenseMatrix(), m1up);
+  VERIFY_IS_APPROX(m1up.template selfadjointView<Upper>().template triangularView<Upper>().toDenseMatrix(), m1up);
+  VERIFY_IS_APPROX(m1.template selfadjointView<Upper>().template triangularView<Lower>().toDenseMatrix(), m1up.adjoint());
+  VERIFY_IS_APPROX(m1up.template selfadjointView<Upper>().template triangularView<Lower>().toDenseMatrix(), m1up.adjoint());
+
 }