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

Ivan Miljenovic wrote:

On 8 July 2010 13:48, Ertugrul Soeylemez wrote:

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Ivan Miljenovic wrote:

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mtl's advantages: wide pre-existing user base, etc.

As said, I don't think this is a valid argument.  Windows has a much larger user base than Linux.  C++ has a much larger user base than Haskell.  We still use Haskell, and many of us use Linux.

My point was, was that if you need to pick a monad transformer library and you've never done any before, then some people are likely to choose mtl because it's currently the most-used library, it comes with the platform and if they need to interact with another package that uses a monad transformer library then it's more likely to be using mtl than anything else.

Yes, that's true. And my point is that that doesn't mean you shouldn't use anything else.

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transformers (especially when used with monads-{fd,tf}) advantage over monadLib: pre-existing type aliases, documentation, easier to port old code that was using mtl.

If you don't use monadLib-specific features, then most code will run in monadLib as well as transformers without changes.  The Haddock documentation of monadLib is quite brief, but if you know how to use monad transformers, you won't have any problems.

I for one don't know how to use monad transformers (I mean, I've read the section in RWH and could figure it out, but off the top of my head I can't recall how to do all the lifting stuff, etc.).

They are easy to use and very useful, especially to make code more modular. You should try them out.

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And I don't know what you mean by "pre-existing type aliases".

http://hackage.haskell.org/packages/archive/transformers/0.2.1.0/doc/html/Co...

MonadLib has newtypes instead of type aliases for them. But the implementations are the same (M = MT Id). Interestingly I need transformers much more often than ready-made monads. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/