toEnum is partial. If the type is not only Enum but also Bounded it's simple enough to implement a non-partial version, e.g.
toEnumSafe :: forall a. (Enum a, Bounded a) => Int -> Maybe a
toEnumSafe i = guard (inBounds i) $> toEnum i where
inBounds = inRange $ join bimap (fromEnum @a) (minBound, maxBound)
{-# INLINE toEnumSafe #-} -- the hope is most of 'inBounds' can be evalueated at compile time if 'a' is known
(inRange is defined in Data.Ix)
There are versions of this in relude and safe. It's occasionally very useful.
toEnumis partial. If the type is not onlyEnumbut alsoBoundedit's simple enough to implement a non-partial version, e.g.(
inRangeis defined inData.Ix)There are versions of this in
reludeandsafe. It's occasionally very useful.