[Haskell-cafe] liftN

[adam vogt]

On Thu, Oct 17, 2013 at 3:19 PM, Wvv <vitea3v at rambler.ru> wrote:
> Nice! Thanks!
>
> As I understand, your solution it is not liftN, but another nice function:
> liftUp (it lifts up to Monad).

The simpler liftN I wrote seems to be the same as
http://hackage.haskell.org/package/layers-0.1/docs/Control-Monad-Layer.html#t:lift

In the LiftN_ module, the expression (liftN (Proxy :: Proxy 3)) has
the same type as the example (lift . lift . lift) you gave, and the
recursion in the class instance look pretty much repeats the lift .
(liftN (n-1)) you wrote.

On the other hand, I'm not sure what you're expecting from the type
signature you wrote for liftN. Promoted types don't have values, which
is why things like f :: True and  g :: 'False -> () are kind errors.

--
Adam