(STRATEGY
    INNERMOST)

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