Hello, After days of effort, I finally managed to compile and install a Haskell compiler. The one I have is NHC98. So now, with my new toy, I am eager to compile my very first Haskell program (I've been using 'runhugs' so far). But I'm having problems: ---<quote>---- $ nhc98 prng.hs -o prng I/O error (user-defined), call to function `userError': In file ./RC4.hi: 1:1-1:6 Found _module_ but expected a interface ---<quote>---- Okay, so I need to learn what an interface is. It looks like Hugs and NHC98 have idfferent ideas of what's acceptable. The file prng.hs starts with: ---<quote>---- module Main where import RC4 .... ---<quote>---- And the file RC4.hs contains all the interesting code. So that's where I am. I'm not clear what it is NHC98 is complaining about or how to fix it. It looks like it doesn't like modules and it wants an interface instead. Can someone point me to where I can learn what an interface is? and how to turn my module into one? Or else, how to make NHC98 accept the module. Any help would be much appreciated. Cheers, Daniel.