Hi,

Two functions from one of Yampa's auxiliary modules have become generally useful (they were made public and they have found use in games, other applications, and other libraries):

dup :: a -> (a, a)
dup x = (x, x)

arr2 :: Arrow a => (b -> c -> d) -> a (b, c) d
arr2 = arr . uncurry

Would you consider adding them to base?

I'd say the logical place for dup would be Data.Tuple and for arr2 would be Control.Arrow.