A solution to a problem (https://www.hackerrank.com/challenges/pangrams) someone (http://chat.stackoverflow.com/transcript/message/19783858#19783858) asked me to solve.

pangram.hs

import Data.Char (toLower)

isPangram :: String -> Bool
isPangram s =
    let ls = map (toLower) s
    in null . filter (not . (`elem` ls)) $ ['a'..'z']

main :: IO ()
main = do
    s <- getLine
    if isPangram s
        then putStrLn "pangram"
        else putStrLn "not pangram"