% The Kahan example. In exact arithmetic f/e = 0/0:
clc
format long

h = 1./2.;

x = 2./3. - h;
e = (x+x+x) - h

y = 3./5. - h;
f = (y+y+y+y+y)-h

z = f/e

disp(sprintf('\nz = %10.5f',z))