[Haskell-cafe] Re: Transformers versus monadLib versus...
es at ertes.de
Tue Jul 6 11:02:54 EDT 2010
Yves Parès <limestrael at gmail.com> wrote:
> Yes but, for instance, every library which provides monad transformers
> will provides a MTL's MonadTrans instance, not a monadLib's MonadT
> instance. And since a library hides its types internals, you cannot
> write the MonadT instances yourself.
> For instance, I was planning to translate a little program of mine
> (which uses quite heavily monad transformers) to monadLib. It uses the
> packages operational which is based on MTL, and I cannot make myself
> operational's transformers instances of MonadT.
> How would you solve that?
You don't, unfortunately. I would probably use both mtl and monadLib or
even rewrite 'operational' to support monadLib.
> (btw, I like the fact that monadLib provides IdT ^^ (IdentityT))
Haven't found a use for it though. =)
nightmare = unsafePerformIO (getWrongWife >>= sex)
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