(VAR f x xs y )
(RULES 
        app(id,x) -> x
        app(add,0) -> id
        app(app(add,app(s,x)),y) -> app(s,app(app(add,x),y))
        app(app(map,f),nil) -> nil
        app(app(map,f),app(app(cons,x),xs)) -> app(app(cons,app(f,x)),app(app(map,f),xs))
        
)