规范模块目录和第三方依赖结构

third_party/eigen3/doc/snippets/MatrixBase_transpose.cpp

@@ -0,0 +1,8 @@
+Matrix2i m = Matrix2i::Random();
+cout << "Here is the matrix m:" << endl << m << endl;
+cout << "Here is the transpose of m:" << endl << m.transpose() << endl;
+cout << "Here is the coefficient (1,0) in the transpose of m:" << endl
+     << m.transpose()(1,0) << endl;
+cout << "Let us overwrite this coefficient with the value 0." << endl;
+m.transpose()(1,0) = 0;
+cout << "Now the matrix m is:" << endl << m << endl;