(VAR x xs y )
(STRATEGY INNERMOST)
(RULES 
        double(0) -> 0
        double(s(x)) -> s(s(double(x)))
        del(x,nil) -> nil
        del(x,cons(y,xs)) -> if(eq(x,y),x,y,xs)
        if(true,x,y,xs) -> xs
        if(false,x,y,xs) -> cons(y,del(x,xs))
        eq(0,0) -> true
        eq(0,s(y)) -> false
        eq(s(x),0) -> false
        eq(s(x),s(y)) -> eq(x,y)
        first(nil) -> 0
        first(cons(x,xs)) -> x
        doublelist(nil) -> nil
        doublelist(cons(x,xs)) -> cons(double(x),doublelist(del(first(cons(x,xs)),cons(x,xs))))
        
)