clear
syms x y
f = x*y
x = 5; y = 4.5;

%% eval
eval(f)
class(ans)
f
disp('-----')

%% subs
clear
syms x y
f = x*y;
x = 5; y = 4.5;
subs(f)
class(ans)
f
disp('-----')

%% partial eval: is it still symbolic or an error?
clear
syms x y
f = x*y;
y = 4.5;
eval(f)
class(ans)
f
disp('-----')

%% partial subs
clear
syms x y
f = x*y;
y = 4.5;
subs(f)
class(ans)
f

disp('-----')
%% evals to double?
clear
g = sin(sym(2))
eval(g)
class(ans)
disp('--------')
%% partial eval?
syms x
g = sin(sym(2))*x
eval(g)
class(ans)

g = sin(sym(2))*sym('pi')*x
eval(g)
class(ans)