[ac]

Depends on what you are doing. The library eco-system used to be a weak link in Haskell, but I see it improving. To clarify, there were (and still are) a lot of broken and/or poorly documented and/or unmaintained libraries on Hackage. Or several libraries for doing the same thing where there is no indication of which library is the best choice. I suspect that is, to some degree, the case in any open-source eco-system, thought. Recently, though, thanks to the effort of the giants like Edward Kmett there have been an influx of great well-documented libraries on Hackage. And of course, you are welcome to contribute new packages/improvements to existing packages.

Working with DBs is easy, especially if you use HaskellDB. There are bindings for non-relational DBs, as well as a DB written in Haskell (acid-state).

As for the language itself, you might find it tricky to develop computation intensive applications with large run-time data-sets due to garbage collection (but that is true for any garbage collected language). Other than that, it's one of the best performing languages in the Debian PL shootout. And the fact that concurrency is (comparatively) easy means you can make use of those extra cores.

Monad transformers and monads are fine, you just need to learn how to use them.

To sum up: it depends on what you do and what you consider a "real world application". Might be a good idea to elaborate. For example, are compilers, games, web apps, automated trading systems, android apps considered "real world"? Because any of these has been done in Haskell.

[raphinou]

I mentioned real world app to mean "not a toy project". That is, i meant a reasonably large, structured, maintainable code base. I am thinking of haskell as the language to use for a new project, and am interested to know more about the potential problems and downsides i should be aware of. Also are there situations where one should absolutely avoid haskell?

[ac]

Yes, I think you should avoid Haskell (and any language with managed memory) on embedded systems or in very performance critical applications. Beyond that, it's going to be a choice of whether there are enough well-supported libraries that help your cause versus some other language. It would help to know in what domain is your new project is going to be.

You've mentioned web apps, so, to be specific, I think the Haskell web app frameworks (Happstack, Yesod and Snap) are mature. There aren't nearly as many utility libraries, as there are, say, for Rails. But that, in my opinion, is compensated by greater correctness guarantees and performance.

I'd encourage you to join the haskell-cafe [1] mailing list: it's a great place to get help if you get stuck.

[1] http://www.haskell.org/mailman/listinfo/haskell-cafe

[DanWaterworth]

> Yes, I think you should avoid Haskell (and any language with managed memory) on embedded systems or in very performance critical applications.

You're forgetting about atom, http://hackage.haskell.org/package/atom.

[mightybyte]

I think that the larger your project gets, the more Haskell will prove to be a win compared to other languages. The value of Haskell's type system in aiding the management and maintenance of large codebases is difficult to overstate.