Re: [Haskell-cafe] Trying to write 'safeFromInteger'

On Tue, 7 Apr 2009, Max Rabkin wrote:

The problem with your code is that the type of maxBound is unspecified. You need (maxBound `asTypeOf` i), or enable ScopedTypeVariables and use (maxBound :: a) (I think).

i is Integer, so asTypeOf is not so easy to apply. I propose to write safeFromIntegerAux :: (Num a, Integral a) => a -> Integer -> Maybe a safeFromIntegerAux mb i =    if i > toInteger mb      then Nothing      else Just (fromInteger i) safeFromInteger = safeFromIntegerAux maxBound Btw. this is another instance where my beloved toMaybe function is useful. :-) http://hackage.haskell.org/packages/archive/utility-ht/0.0.4/doc/html/Data-M...