(VAR f g x xs )
(RULES 
        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))
        app(app(app(comp,f),g),x) -> app(f,app(g,x))
        app(twice,f) -> app(app(comp,f),f)
        
)