Tutorial page 3: add more cwise operations, condense rest.

doc/examples/Tutorial_ArrayClass_addition.cpp

@@ -8,15 +8,16 @@ int main()
 {
   ArrayXXf a(3,3);
   ArrayXXf b(3,3);
-  
   a << 1,2,3,
        4,5,6,
        7,8,9;
-
   b << 1,2,3,
        1,2,3,
        1,2,3;
        
-  cout << "a + b = " << endl
-       << a + b << endl;
+  // Adding two arrays
+  cout << "a + b = " << endl << a + b << endl << endl;
+
+  // Subtracting a scalar from an array
+  cout << "a - 2 = " << endl << a - 2 << endl;
 }