Nothing controversial said here... I'm just agreeing with Russel. On Tue, May 12, 2009 at 4:03 PM, <rocon...@theorem.ca> wrote:
> I wanted to pass this idea around the cafe to get some thoughts before > submitting a trac on this topic. > > I'd like to see the mtl removed from the Haskell Platform. > > The mtl was a tremendous step forward when it was developed. However, we > have learned a few things about monad transformers since the development of > the mtl, and it is time that we moved forward. > > There are at least 3 significant problem with the mtl. > > 1) `pass' should not be a member functions of the MonadWriter class. It is > my understanding that there is no `MonadWriter w m => MonadWriter w (ContT s > m)' instance because the `pass' function cannot be implemented. I'm also > highly suspicious of some other methods too (I'm looking at you `local'). > > 2) The `StateT s (Cont r a)' instance of callCC is wrong. The paper on > modular monad transformers <http://www.cs.nott.ac.uk/~mjj/pubs/mmt/mmt.pdf> > describes why this is wrong. > > 3) I am told by many people that the order of the state and value pair in > `State' is backwards. Actually, I'm not entirely sure what the issue is > here, but I trust the people who say this. > > I think that use of the mtl should be deprecated so that we move on to > improved monad transformer libraries. Having the mtl in the Haskell > Platform does the opposite by further entrenching its use, possibly to the > point where we may not be able to get rid of it for years. > > If I had to recommend a replace library, I would pick monadLib. However, > there are other libraries, such as the mmtl and transformers and it's > related packages that I haven't looked at, and may also make fine > replacements for the mtl. > > -- > Russell O'Connor <http://r6.ca/> > ``All talk about `theft,''' the general counsel of the American Graphophone > Company wrote, ``is the merest claptrap, for there exists no property in > ideas musical, literary or artistic, except as defined by statute.'' > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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