Proposal for removing transformers dependency

Alexander V Vershilov alexander.vershilov at
Wed Jan 21 16:19:42 UTC 2015

I thought about providing package ghc-transformers-instances, that will
provide instances for transformers's type classes for user. So
ghc-tf-instances will depend on current ghc, and current transformers that
could be provided by user environment.
On Jan 21, 2015 7:15 PM, "Herbert Valerio Riedel" <hvriedel at>

> On 2015-01-21 at 16:51:55 +0100, Alexander V Vershilov wrote:
> [...]
> > As transformers usage are quite limited in ghc, and it's really relevant
> > in ghc-bin, it's possible to duplicate the code, and provide required
> > fixes in ghc-bin.cabal. As a result ghc uses it's own MonadIO,
> MonadControl
> > and Strict State, and ghc-bin.cabal (ghc/*) uses ones from
> > transformers.
> ...but doesn't this effectively mean that the instances provided by the
> `ghc` package are of little use or rather can't be easily combined with
> code that builds on top of the original `transformers` classes everyone
> else uses?
> Cheers,
>   hvr
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