I think you are correct that the language does think of all expressions in terms of thunks, but I'm guessing `4 + 5` won't actually be run at run-time! Since i

I think you are correct that the language does think of all expressions in terms of thunks, but I'm guessing `4 + 5` won't actually be run at run-time! Since it's pure a decent compiler should be able to simply replace any `x` with the number 9 - correct me if I'm wrong :) Any primitive (C code) however won't run until run-time, which is probably the pressing reason putStr doesn't run until run-time (and that's a good thing :)