nrujac at gmail.com
Thu Oct 17 18:05:30 UTC 2013
This is slightly off-topic, but you might be interested in the
that obviates the need for a function like liftN.
On Thu, Oct 17, 2013 at 1:44 PM, Wvv <vitea3v at rambler.ru> wrote:
> Thank you!
> Unfortunately, liftN always take same number of arguments.
> So, polyvariadic "magic" don't work here.
> wren ng thornton wrote
> > On 10/16/13 5:06 PM, Wvv wrote:
> >> I try to write a function "liftN", but I'm not satisfied with result.
> >> lift :: (MonadTrans t) => Monad m => m a -> t m a
> >> liftN n
> >> | n < 1 = error "liftN: n<1"
> >> | n == 1 = lift
> >> | otherwise = lift . (liftN (n-1))
> >> 1) I know(?), that it is impossible to write liftN now: typechecker
> >> decide which signature it is.
> > You should check out the solutions for encoding polyvariadic functions,
> > e.g.
> > *
> > <
> > * <http://okmij.org/ftp/Haskell/polyvariadic.html#polyvartype-fn>
> > * <
> > *
> > <
> > --
> > Live well,
> > ~wren
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