October 2015 1HaskellADay 1-Liners

• October 15th, 2015: Matrix-themed problem
  dotProduct :: Num a => [a] -> [a] -> a
  dotProduct a b = sum (zipWith (*) a b)
  point-free-itize the definition
• Freddy Román @frcepeda dotProduct = sum `dot` zipWith (*) where dot = (.).(.)
• October 13th, 2015: You're given either fst or snd, but don't know which. Define a function that returns its dual:
  dual :: ((a,a) -> a) -> ((a,a) -> a)
  n.b.: The tuples here have BOTH fst and snd as the same type: a
  Also, a-values have NO typeclass constraints. You CAN NOT use (==) nor (>)
• Michael Thomas @mjtjunior dual f = f (snd,fst)
• Francisco Soares Nt @frsoares dual = uncurry . flip . curry
• Fernando Castor @fernandocastor dual f = \(x,y) -> f (y, x)
  (I hadn't seen @mjtjunior's answer beforehand)
• Андреев Кирилл @nonaem00 (. Data.Tuple.swap)