Is there a reason there is no `modify` operation in Control.Monad.State.Strict (and the transformers analogue) which is truly strict in the state? That is, modify' :: Monad m => (a -> a) -> StateM a m () modify' f = get >>= (\x -> put $! f x) While this is admittedly not a difficult piece of code to write, even the suggestion in the documentation that `modify` isn't as strict as one might think would likely save many man-hours of debugging (especially for those who are less familiar with the language, for whom, speaking from experience, strictness issues can pose a major hurdle to adoption) In general it would be nice if the notion of strictness were better addressed in the major libraries' documentation. It's a nuanced issue which is not fully captured by a ".Lazy" or ".Strict" in the module name. Just a thought. Thanks, - Ben