initial commit

third_party/eigen/doc/examples/TemplateKeyword_flexible.cpp

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+#include <Eigen/Dense>
+#include <iostream>
+
+template <typename Derived1, typename Derived2>
+void copyUpperTriangularPart(Eigen::MatrixBase<Derived1>& dst, const Eigen::MatrixBase<Derived2>& src) {
+  /* Note the 'template' keywords in the following line! */
+  dst.template triangularView<Eigen::Upper>() = src.template triangularView<Eigen::Upper>();
+}
+
+int main() {
+  Eigen::MatrixXi m1 = Eigen::MatrixXi::Ones(5, 5);
+  Eigen::MatrixXi m2 = Eigen::MatrixXi::Random(4, 4);
+  std::cout << "m2 before copy:" << std::endl;
+  std::cout << m2 << std::endl << std::endl;
+  copyUpperTriangularPart(m2, m1.topLeftCorner(4, 4));
+  std::cout << "m2 after copy:" << std::endl;
+  std::cout << m2 << std::endl << std::endl;
+}