From c6f610093bff10c5a6e4fac94bfed422ba54b39a Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Sun, 5 Jul 2009 11:33:55 +0200
Subject: add a VectorBlock expr as a specialization of Block

---
 doc/examples/class_FixedVectorBlock.cpp | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 doc/examples/class_FixedVectorBlock.cpp

(limited to 'doc/examples/class_FixedVectorBlock.cpp')

diff --git a/doc/examples/class_FixedVectorBlock.cpp b/doc/examples/class_FixedVectorBlock.cpp
new file mode 100644
index 000000000..c176be495
--- /dev/null
+++ b/doc/examples/class_FixedVectorBlock.cpp
@@ -0,0 +1,26 @@
+#include <Eigen/Core>
+USING_PART_OF_NAMESPACE_EIGEN
+using namespace std;
+
+template<typename Derived>
+Eigen::VectorBlock<Derived, 2>
+firstTwo(MatrixBase<Derived>& v)
+{
+  return Eigen::VectorBlock<Derived, 2>(v.derived(), 0);
+}
+
+template<typename Derived>
+const Eigen::VectorBlock<Derived, 2>
+firstTwo(const MatrixBase<Derived>& v)
+{
+  return Eigen::VectorBlock<Derived, 2>(v.derived(), 0);
+}
+
+int main(int, char**)
+{
+  Matrix<int,1,6> v; v << 1,2,3,4,5,6;
+  cout << firstTwo(4*v) << endl; // calls the const version
+  firstTwo(v) *= 2;              // calls the non-const version
+  cout << "Now the vector v is:" << endl << v << endl;
+  return 0;
+}
-- 
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