From ce2035af868d57b85b4078c15843d5c1f51047dc Mon Sep 17 00:00:00 2001
From: Jitse Niesen <jitse@maths.leeds.ac.uk>
Date: Sat, 27 Sep 2014 23:25:58 +0100
Subject: New doc page on implementing a new expression class.

---
 doc/examples/make_circulant.cpp.evaluator | 33 +++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 doc/examples/make_circulant.cpp.evaluator

(limited to 'doc/examples/make_circulant.cpp.evaluator')

diff --git a/doc/examples/make_circulant.cpp.evaluator b/doc/examples/make_circulant.cpp.evaluator
new file mode 100644
index 000000000..98713cdc0
--- /dev/null
+++ b/doc/examples/make_circulant.cpp.evaluator
@@ -0,0 +1,33 @@
+namespace Eigen {
+  namespace internal {
+    template<typename ArgType>
+    struct evaluator<Circulant<ArgType> >
+      : evaluator_base<Circulant<ArgType> >
+    {
+      typedef Circulant<ArgType> XprType;
+      typedef typename nested_eval<ArgType, XprType::ColsAtCompileTime>::type ArgTypeNested;
+      typedef typename remove_all<ArgTypeNested>::type ArgTypeNestedCleaned;
+      typedef typename XprType::CoeffReturnType CoeffReturnType;
+      typedef typename XprType::Index Index;
+
+      enum { 
+        CoeffReadCost = evaluator<ArgTypeNestedCleaned>::CoeffReadCost,
+        Flags = Eigen::ColMajor 
+      };
+      
+      evaluator(const XprType& xpr)
+        : m_argImpl(xpr.m_arg), m_rows(xpr.rows())
+      { }
+
+      CoeffReturnType coeff(Index row, Index col) const
+      {
+        Index index = row - col;
+        if (index < 0) index += m_rows;
+        return m_argImpl.coeff(index);
+      }
+
+      typename evaluator<ArgTypeNestedCleaned>::nestedType m_argImpl;
+      const Index m_rows;
+    };
+  }
+}
-- 
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