Efficient algorithm for finding minimum and maximum value from sequence

minmax.hs

import Data.Tuple (swap)
import System.Environment (getArgs)

minmax (a:b:xs) = foldl (minmax') (sort' (a, b)) (pairs xs)
    where minmax' (curmin, curmax) candidates = (newmin, newmax)
              where (cmin, cmax) = sort' candidates
                    newmin = if cmin < curmin then cmin else curmin
                    newmax = if cmax > curmax then cmax else curmin

sort' tup@(a, b) = if a <= b then tup else swap tup

pairs :: [a] -> [(a, a)]
pairs (a:b:as) = (a, b):(pairs as)
pairs (c:[]) = (c, c):[]
pairs [] = []

main = do
    args <- getArgs
    let [from, till] = map read args :: [Int]
    print $ minmax [from..till]