Add ifThenElse and (?) to Data.Bool

[Henning Thielemann]

On Thu, 17 Nov 2016, Yitzchak Gale wrote:

> Anyway, bool is the natural parameter order in Haskell.
> I'll make more explicit what others have already said, with
> this analogy:
>
> maybe (if it fails) (if it succeeds) (input data)
> either (if it fails) (if it succeeds) (input data)

> foldl (if it's null) (if it's not null) (input data)
> foldr (if it's null) (if it's not null) (input data)

Unfortunately, it is the other way round:

foldl (if it's not null) (if it's null) (input data)
foldr (if it's not null) (if it's null) (input data)