It isn't, in ghci try ":m + Data.Traversable" and ":info (->)". It should be possible to define an "instance Bounded a, Enum a, Eq a) => Traversable ((->) a)", it would only work on total functions with finitely enumerable inputs. It would be exactly like "Ord a => Traversable (Map a)", except it also needs to convert the function into this map representation by enumerating all inputs. With just the Eq constraint, the resulting function would be very inefficient as it would need to scan all (input, output) pairs to find the matching one. So you'd probably want an Ord or Hashable constraint and use Map or HashMap. Since this process is so slow, it doesn't make much sense to have this instance defined, it is not a very normal thing to do with functions. More likely to cause confusing type errors when the user intended to use traverse with some other type. -Michael On Wed, Sep 20, 2017 at 10:33 AM, David Banas wrote:

Is there a Traversable instance for ((->) a)? -db

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