On Mon, Aug 9, 2010 at 3:42 PM, Job Vranish wrote:
> For monads like StateT, WriterT, ReaderT, the order doesn't matter (except
> perhaps for some pesky performance details). However, for monad transformers
> like ErrorT or ListT, the order _does_ matter.
Is it really correct to say that order do
I've never used this myself, but the package mtlx seems to offer one
possible solution to this problem by tagging the monad transformers with
index types:
http://hackage.haskell.org/package/mtlx
Cheers,
Greg
On 08/09/10 12:39, Gábor Lehel wrote:
> Actually, while I haven't even used monad t
2010/8/9 Edward Z. Yang :
> Excerpts from Gábor Lehel's message of Mon Aug 09 15:39:49 -0400 2010:
>> Actually, while I haven't even used monad transformers before (just
>> read about them a lot), I was thinking that something like this might
>> be the way to solve the lift . lift . lift . lift . f
Excerpts from Gábor Lehel's message of Mon Aug 09 15:39:49 -0400 2010:
> Actually, while I haven't even used monad transformers before (just
> read about them a lot), I was thinking that something like this might
> be the way to solve the lift . lift . lift . lift . foo problem on the
> one hand, a
For monads like StateT, WriterT, ReaderT, the order doesn't matter (except
perhaps for some pesky performance details). However, for monad transformers
like ErrorT or ListT, the order _does_ matter.
The code you have there is perfectly fine, sometimes the added generality
can be quite handy (espec
Actually, while I haven't even used monad transformers before (just
read about them a lot), I was thinking that something like this might
be the way to solve the lift . lift . lift . lift . foo problem on the
one hand, and by wrapping the 'contents' (e.g. the environment of a
reader monad) of every
Excerpts from aditya siram's message of Mon Aug 09 15:05:14 -0400 2010:
> Until test is called in 'main' we don't know the order of monads. In fact
> even the base monad is not know. All we know is that it uses the State and
> Writer monad. In each call to 'test' in main we can determine the stacki
Hi all,
I was experimenting with monad transformers and realized that the stacking
order of the monads can remain unknown until it is used. Take for example
the following code:
import "mtl" Control.Monad.State
import "mtl" Control.Monad.Writer
import "mtl" Control.Monad.Identity
test :: (MonadWri
