(STRATEGY
    INNERMOST)

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