Solve SEND+MORE=MONEY puzzle with Haskell

main.hs

main = do
    print "(s,e,n,d,m,o,r,y)"
    print solveSendMoreMoney

--   S E N D
-- + M O R E
-- ---------
-- M O N E Y
-- where M /= 0 and every digit stands for a different (unique) number

solveSendMoreMoney = head [(s,e,n,d,m,o,r,y) |
    s <- [0..9],
    e <- [0..9],
    n <- [0..9],
    d <- [0..9],
    m <- [1..9], -- [sic!]
    o <- [0..9],
    r <- [0..9],
    y <- [0..9],
    unique (s:e:n:d:m:o:r:y:[]),
    s * 1000 + e * 100 + n * 10 + d +
    m * 1000 + o * 100 + r * 10 + e ==
    m * 10000 + o * 1000 + n * 100 + e * 10 + y]
    
unique [] = True
unique [x] = True
unique (x:xs) = not (x `elem` xs) && unique xs