I've wondered for a while why Haskell 98 didn't provide strictness annotations for functions a la Clean and no implementations provide it as an extension (actually I don't know about NHC, but I'm pretty sure neither GHC nor Hugs do). Clean's solution seems easier to read and write and seems like it would be trivial (though possibly tedious) to implement. So my questions are: What was the motivation for not providing them in Haskell 98? Are there any technical problems with adding them to Haskell now (or then)? If there aren't any issues, are strictness annotations on any implementors' wish-list to be added when there is sufficient demand or no more pressing matters? Googling the haskell archives didn't (immediately at least) turn up any answers to these questions, but did turn up a couple posts suggesting the desirability this. http://www.haskell.org/pipermail/haskell/2002-March/009176.html http://www.haskell.org/pipermail/haskell-cafe/2001-June/001995.html