Ross Paterson
When I've used seq, it's to ensure that a function is strict in that argument, and therefore has been evaluated before the function is called. (If the language had unlifted types, I might have used those instead). Beyond that, I don't care exactly when it was evaluated; it might be long before, thanks to propagation of strictness information.
When I use `seq`, it is sometimes in a construction like unsafePerformIO (emit "squawk!) `seq` x where I am trying to force the impure side-effect to happen, exactly and immediately before x is evaluated. Whilst this is not good style in a general sense, I argue that it is perfectly safe inside certain kinds of library (e.g. for calculating coverage information, or for emitting tracing information). But if the language itself cannot guarantee this exact placement of side-effects, then it becomes impossible to write computation-reflective tools like Hat and hpc for Haskell, in Haskell. That would surely be a sad state of affairs. Regards, Malcolm