Grouping numbers together in Haskell

grp.hs

-- Group blocks together.

import Data.List (intersperse)

grp :: [Int] -> [(Int,Int)]
grp [] = []
grp (x:xs) = pair x x xs where
	pair lo hi (x:xs) | x == hi + 1 = pair lo x xs
	pair lo hi xs | otherwise = (lo,hi): grp xs


displayGroup :: [(Int,Int)] -> String
displayGroup = concat . intersperse "," . map displayPair where
	displayPair (x,y) = if x == y then show x
		else show x ++ "-" ++ show y

{-|

> grp [1,2,3,4,5,8,9,20,21,22,23,24,25,30]
[(1,5),(8,9),(20,25),(30,30)]

> displayGroup $ grp [1,2,3,4,5,8,9,20,21,22,23,24,25,30]
"1-5,8-9,20-25,30"

-}