# define a table for the convolution
table w % 11 -5 5 1/11
# define h(u-theta)
h[0..100]=heav(u[j]-theta)
# define the special convolution operator
special k=conv(zero,101,5,w,h0)
u[0..100]'=-u[j]+k([j])
init u0=1,u1=1,u2=1
par theta=.1
done