added some things for sec 1

sec1_preliminaries.m

@@ -8,3 +8,29 @@ w = x + y;
 z = w * y; 
 z = 4 * z;         % z = 4 * (x + y) * y
 J = jacobian(z,y); % node in graph
+
+%% Function
+f = Function('f' , {x, y}, {z});
+r = f(1, 2)   % evaluates the function
+class(r)      % returns the type, casadi.DM 
+r2 = full(r)  % converts from DM to double
+class(r2)     % returns the type, double
+
+function [z] = f1(x,y)
+    w = x + y;
+    z = w * y;
+    z = 4 * z;
+end
+r = f1(x, y) % different than Function
+class(r)     % casadi.MX
+
+
+%% 
+x = MX.sym('x');
+y = MX.sym('y');
+w = x + y;
+z = w * y; 
+z = 4 * z;         % z = 4 * (x + y) * y
+
+f2 = Function('f' , {x, y}, {z});
+f3 = Function('f' , {x, y}, {4 * (x + y) * y});
\ No newline at end of file

sec2_functions.m

@@ -32,4 +32,3 @@ disp(fMX, true);
 
 disp('Function fSX: ');
 disp(fSX, true);
-