I wrote:
But the list monad [] is not a transformer, so you can't lift in it,
even if the contained type happens also to be a monad.
Andrew Bromage wrote:
ListT is also not a transformer.
True, unfortunately. But it does provide MonadTrans
and MonadIO instances that solve problems like
this in practice.
What can be done to get an improved list transformer
into MTL?
See here for details:
http://www.haskell.org/hawiki/ListTDoneRight
Can someone with permissions on the new wiki please
get this important page moved over?
Thanks,
Yitz
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