Lyndon Maydwell
I thought it was pure as, conceptually, readFile isn't 'run' rather it constructs a pure function that accepts a unique world state as a parameter. This might be totally unrealistic, but this is how I see IO functions remaining pure. Is this a good mental model?
Yes, but some people argue that there are problems with this model. For example it doesn't really catch the forkIO concept and the interactions between threads. For this model, forkIO is just a side effect like everything else and if you takeMVar a value, then it comes "from the world", which isn't very useful. But don't bother, because that model works most of the time. Personally I have switched from your model to the model of an embedded DSL. It's a simpler mental model and doesn't interpret too much. You just get some primitive IO computations and a number of combinators to stick them together. That's it. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/