(VAR x y z)
(RULES
fib(0) -> 0
fib(s(0)) -> s(0)
fib(s(s(x))) -> +(fib(s(x)),fib(x))
+(x,0) -> x
+(x,s(y)) -> s(+(x,y))
)
(COMMENT Example 2.25 (Fibonacci Function) in \cite{SK90})