add example to the documentation

doc/CMakeLists.txt

@@ -1 +1,3 @@
 add_executable(tutorial tutorial.cpp)
+add_executable(example example.cpp)
+

doc/example.cpp

@@ -0,0 +1,28 @@
+#include "../src/All"
+
+using namespace std;
+
+template<typename Scalar, typename Derived>
+void foo(const EiObject<Scalar, Derived>& m)
+{
+	cout << "Here's m:" << endl << m << endl;
+}
+
+template<typename Scalar, typename Derived>
+EiScalarProduct<Derived>
+twice(const EiObject<Scalar, Derived>& m)
+{
+	return static_cast<Scalar>(2) * m;
+}
+
+int main(int, char**)
+{
+	EiMatrix2d m;
+	m(0,0)= 1;
+	m(1,0)= 2;
+	m(0,1)= 3;
+	m(1,1)= 4;
+	foo(m);
+	foo(twice(m));
+	return 0;
+}

doc/tutorial.cpp

@@ -43,7 +43,7 @@ int main(int, char **)
        << "overwritten _while_ the matrix product m * m is being computed." << endl
        << "This is the counterpart of eliminating temporary objects!" << endl
        << "Anyway, if you want to store m * m into m, you can do this:" << endl
-       << "            m = eval(m * m);" << endl;
+       << "            m = (m * m).eval();" << endl;
   m = m_save;
   m = (m * m).eval();
   cout << "And m is now:" << endl << m << endl << "as was expected." << endl;