A solution to https://exercism.org/tracks/haskell/exercises/pangram

pangram.hs

module Pangram (isPangram) where

import Data.Char
import Data.Bits 

charToBit :: Char -> Int
charToBit c = let bit = (fromEnum c .|. 32) - 97 in 
              if bit >=0 && bit < 26 then 2 ^ bit else 0

bitsum :: String -> Int
bitsum txt = foldl (.|.) 0 (map charToBit txt)

isPangram :: String -> Bool
isPangram text = 2^26-1 == bitsum text

qbf="The quick brown fox jumps over the lazy dog"
main = do
    print $ isPangram qbf
    print $ isPangram "not a pangram"