1. fst, snd, swap

-- | Extract the first component of a pair.
fst                     :: (a,b) -> a
fst (x,_)               =  x

-- | Extract the second component of a pair.
snd                     :: (a,b) -> b
snd (_,y)               =  y

-- | Swap the components of a pair.
swap                    :: (a,b) -> (b,a)
swap (a,b)              = (b,a)


2. curry, uncurry
-- | 'curry' converts an uncurried function to a curried function.
curry                   :: ((a, b) -> c) -> a -> b -> c
curry f x y             =  f (x, y)

-- | 'uncurry' converts a curried function to a function on pairs.
uncurry                 :: (a -> b -> c) -> ((a, b) -> c)
uncurry f p             =  f (fst p) (snd p)

3. Uncurry
http://ro-che.info//articles/2013-01-29-generic-uncurry.html