(STRATEGY
    INNERMOST)

(VAR
    x y)
(DATATYPES
    A = µX.< 0, s(X) >)
(SIGNATURES
    - :: [A x A] -> A
    p :: [A] -> A
    f :: [A x A] -> A)
(RULES
    -(x,0()) -> x
    -(s(x),s(y)) -> -(x,y)
    p(s(x)) -> x
    f(s(x),y) -> f(p(-(s(x),y))
                  ,p(-(y,s(x))))
    f(x,s(y)) -> f(p(-(x,s(y)))
                  ,p(-(s(y),x))))