(STRATEGY
    INNERMOST)

(VAR
    X X1 X2 Y Z)
(DATATYPES
    A = µX.< 0, nil, s(X), cons(X, X), fst(X, X), from(X), add(X, X), len(X) >)
(SIGNATURES
    a__fst :: [A x A] -> A
    a__from :: [A] -> A
    a__add :: [A x A] -> A
    a__len :: [A] -> A
    mark :: [A] -> A)
(RULES
    a__fst(0(),Z) -> nil()
    a__fst(s(X),cons(Y,Z)) ->
      cons(mark(Y),fst(X,Z))
    a__from(X) -> cons(mark(X)
                      ,from(s(X)))
    a__add(0(),X) -> mark(X)
    a__add(s(X),Y) -> s(add(X,Y))
    a__len(nil()) -> 0()
    a__len(cons(X,Z)) -> s(len(Z))
    mark(fst(X1,X2)) ->
      a__fst(mark(X1),mark(X2))
    mark(from(X)) ->
      a__from(mark(X))
    mark(add(X1,X2)) ->
      a__add(mark(X1),mark(X2))
    mark(len(X)) -> a__len(mark(X))
    mark(0()) -> 0()
    mark(s(X)) -> s(X)
    mark(nil()) -> nil()
    mark(cons(X1,X2)) ->
      cons(mark(X1),X2)
    a__fst(X1,X2) -> fst(X1,X2)
    a__from(X) -> from(X)
    a__add(X1,X2) -> add(X1,X2)
    a__len(X) -> len(X))