Simpson's 3/8th Rule (Simple)

disp("------------------------Simpson's 3/8th Rule------------------------")

% str = input('Give an equation in x: ','s')  ;
% a = input('Enter lowerbound value:');
% a
% b = input('Enter upperbound value:');
% b

str = "exp(1)"
a=-1;
b=1;
a
b

h = (b-a)/3;
x1 = a + h;
x2 = a + h + h;
h

% f = inline(str,'x') ;
f = str2func(['@(x) ',str]);

fa = feval(f,a) ;
fb = feval(f,b) ;
fx1 = 3* feval(f, x1) ;
fx2 = 3* feval(f, x2) ;


I = (h/2)*(fa+fx1+fx2+fb);


disp(['Ans: ', num2str(I)])