  Given a continuous function $f(x)$, suppose that the sign of $f$ only has
finitely many discontinuous points in the interval $[0,1]$. We show how to use
a sequence of one dimensional deterministic binary cellular automata to
determine the sign of $f(\rho)$ where $\rho$ is the (number) density of 1s in
an arbitrarily given bit string of finite length provided that $f$ satisfies
certain technical conditions.
