Inspired by conversations recent [1] and not-so-recent [2] and by my own past wish for this, I propose adding the following function to base: toBoundedIntegral :: (Integral a, Integral b, Bounded b) => a -> Maybe b toBoundedIntegral x | y > toInteger (maxBound `asTypeOf` z) = Nothing | y < toInteger (minBound `asTypeOf` z) = Nothing | otherwise = Just $! z where y = toInteger x z = fromInteger y This includes rules to optimize for many cases where we know the bounds at compile time. See the gist for the full implementation: https://gist.github.com/spl/1986c9ff0b2416948957 I'm not particularly concerned with the precise location of this function. It could start out in GHC.Int if there's controversy. Otherwise, Data.Int would be an option to avoid polluting the Prelude. I chose the name to be descriptive of the result type, which is the more constrained type. The function that I started from [2] was called fromIntegralSafe, but I think “safe” is too ambiguous here. I did not find “toBoundedIntegral” in any package on Hackage. I welcome review of the implementation and rules. Discussion period: ~10 days if there is a strong desire to get it in GHC 7.10. (I would certainly like to see it get in.) Otherwise, I can make a package, and we can revisit the issue at another time. Regards, Sean [1] Evan Laforge: http://thread.gmane.org/gmane.comp.lang.haskell.cafe/113600/focus=113648 [2] Stephen Paul Weber: http://thread.gmane.org/gmane.comp.lang.haskell.cafe/102613/focus=64686