Stephen Dolan wrote:
unsafePerformIO is possibly the most ugly feature of Haskell, yet is necessary to do many things which should be possible without it, such as reading configuration from a file at startup or creating global IORefs
There is a considerable debate about global mutable state even in imperative languages. As to reading data from a configuration file -- which should be immutable for the rest of the computation -- one solution has been proposed back in 2002: Pure File Reading (was: Dealing with configuration data) http://www.haskell.org/pipermail/haskell/2002-September/010519.html The problem essentially is of separate compilation and dynamic linking -- both of which are far simpler now than it was in 2002, with GHC API and hs-plugins.