(STRATEGY
    INNERMOST)

(VAR
    x y)
(DATATYPES
    A = µX.< 0, true, s(X), false >)
(SIGNATURES
    leq :: [A x A] -> A
    if :: [A x A x A] -> A
    - :: [A x A] -> A
    mod :: [A x A] -> A)
(RULES
    leq(0(),y) -> true()
    leq(s(x),0()) -> false()
    leq(s(x),s(y)) -> leq(x,y)
    if(true(),x,y) -> x
    if(false(),x,y) -> y
    -(x,0()) -> x
    -(s(x),s(y)) -> -(x,y)
    mod(0(),y) -> 0()
    mod(s(x),0()) -> 0()
    mod(s(x),s(y)) -> if(leq(y,x)
                        ,mod(-(s(x),s(y)),s(y))
                        ,s(x)))