The Q42 e-mail signature as executable Haskell. Returns 42 times Q42 when executed.

signature.hs

{-# LANGUAGE ParallelListComp, MonadComprehensions, RebindableSyntax #-}
import Prelude

data Names = Q42 Names | BV | Names :// (Int -> Int) | Waldorpstraat Int Names | F | Den Names | Haag | KvK Int
instance Show Names where show _ = "Q42"
infixr 9 ://

tel :: Int -> Int -> Int -> Names
tel _ _ _ = F
http :: Names
http = Haag
q42, nl :: Int -> Int
q42 = (+42)
nl = (*5)

guard :: Names -> [()]
guard name = replicate (f name) ()
  where
    f (Q42 n) = 42 * f n
    f BV = 5
    f (_ :// g) = g 4
    f (Waldorpstraat i _) = i - 10
    f F = 100
    f (Den n) = 2 * f n
    f Haag = 3
    f (KvK i) = i
mzip :: [a] -> [b] -> [(a, b)]
mzip = zip

signature :: [Names]
signature = [ Q42 BV | tel 070 44523 42 | http://q42.nl | Waldorpstraat 17F, Den Haag | KvK 30164662 ]