New doc page on implementing a new expression class.

1 files changed, 20 insertions, 0 deletions

diff --git a/doc/examples/make_circulant.cpp.expression b/doc/examples/make_circulant.cpp.expression
new file mode 100644
index 000000000..a68bcb730
--- /dev/null
+++ b/doc/examples/make_circulant.cpp.expression
@@ -0,0 +1,20 @@
+template <class ArgType>
+class Circulant : public Eigen::MatrixBase<Circulant<ArgType> >
+{
+public:
+  Circulant(const ArgType& arg)
+    : m_arg(arg)
+  { 
+    EIGEN_STATIC_ASSERT(ArgType::ColsAtCompileTime == 1,
+                        YOU_TRIED_CALLING_A_VECTOR_METHOD_ON_A_MATRIX);
+  }
+
+  typedef typename Eigen::internal::ref_selector<Circulant>::type Nested; 
+
+  typedef typename Eigen::internal::traits<Circulant>::Index Index;
+  Index rows() const { return m_arg.rows(); }
+  Index cols() const { return m_arg.rows(); }
+
+  typedef typename Eigen::internal::ref_selector<ArgType>::type ArgTypeNested;
+  ArgTypeNested m_arg;
+};