(VAR x y) (RULES D(t) -> 1 D(constant) -> 0 D(+(x,y)) -> +(D(x),D(y)) D(*(x,y)) -> +(*(y,D(x)),*(x,D(y))) D(-(x,y)) -> -(D(x),D(y)) ) (COMMENT Example 8 in \cite{D33})