many small fixes and documentation improvements,
this should be alpha5.
diff --git a/doc/snippets/MatrixBase_extract.cpp b/doc/snippets/MatrixBase_extract.cpp
new file mode 100644
index 0000000..0996ad6
--- /dev/null
+++ b/doc/snippets/MatrixBase_extract.cpp
@@ -0,0 +1,8 @@
+Matrix3i m = Matrix3i::random();
+cout << "Here is the matrix m:" << endl << m << endl;
+cout << "Here is the upper-triangular matrix extracted from m:" << endl
+ << m.extract<Eigen::Upper>() << endl;
+cout << "Here is the strictly-upper-triangular matrix extracted from m:" << endl
+ << m.extract<Eigen::StrictlyUpper>() << endl;
+cout << "Here is the unit-lower-triangular matrix extracted from m:" << endl
+ << m.extract<Eigen::UnitLower>() << endl;