[Haskell-cafe] When using Cereal, what is the right way to write `get` for multi-constructor type?

[Magicloud Magiclouds]

Hi,
Say I have code already like:
data STH = A
        | B
        | C
instance Serialize STH where
  put A = putWord8 1
  put B = putWord8 66
  put C = putWord8 111

Then what is the better way to do `get`? Is following the only one?
get = do
  i <- getWord8
  case i of
    1 -> return A
    66 -> return B
    111 -> return C

Thanks.
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