[Haskell-cafe] Re: Transformers versus monadLib versus...

Yves Parès limestrael at gmail.com
Tue Jul 6 09:29:07 EDT 2010

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?

(btw, I like the fact that monadLib provides IdT ^^ (IdentityT))

2010/7/6 Ertugrul Soeylemez <es at ertes.de>

> Yves Parès <limestrael at gmail.com> wrote:
> > monadLib looks nice, indeed, but the major problem with using it
> > resides in the fact that most of the libraries on hackage use MTL.
> > Must be tedious to have to use two monad libraries at the same time...
> In general this is a minor problem.  Note that when using a monad from
> another library usually you get provided with a type alias (or even a
> newtype) and a number of convenience functions, so you don't have to
> access names from both libraries at the same time.
> I can only speak for myself, but I've never had a problem with this,
> even though my packages often have lots and lots of dependencies.
> Greets,
> Ertugrul
> --
> nightmare = unsafePerformIO (getWrongWife >>= sex)
> http://ertes.de/
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