primFittingAllInts.hs

data Prim
  = PU8
  | PU16
  | PU32
  | PU64
  | PS8
  | PS16
  | PS32
  | PS64
  | PF32
  | PF64
  | PBool
  deriving (Show, Eq, Enum, Bounded)

primFittingAllInts :: [Integer] -> Prim
primFittingAllInts vs
    | (not signed) && all (<= w8max) vs  = PU8
    | (not signed) && all (<= w16max) vs = PU16
    | (not signed) && all (<= w32max) vs = PU32
    | (not signed) && all (<= w64max) vs = PU64

    | (signed) && all (\i -> i8min  <= i && i <= i8max)  vs = PS8
    | (signed) && all (\i -> i16min <= i && i <= i16max) vs = PS16
    | (signed) && all (\i -> i32min <= i && i <= i32max) vs = PS32
    | (signed) && all (\i -> i64min <= i && i <= i64max) vs = PS64

    | otherwise = error $ "Unable to express all values in a single primitive: " ++ show vs
  where
    signed = any (< 0) vs

    w64max = fromIntegral (maxBound :: Word64)
    w32max = fromIntegral (maxBound :: Word32)
    w16max = fromIntegral (maxBound :: Word16)
    w8max  = fromIntegral (maxBound :: Word8)

    i64max = fromIntegral (maxBound :: Int64)
    i32max = fromIntegral (maxBound :: Int32)
    i16max = fromIntegral (maxBound :: Int16)
    i8max  = fromIntegral (maxBound :: Int8)

    i64min = fromIntegral (minBound :: Int64)
    i32min = fromIntegral (minBound :: Int32)
    i16min = fromIntegral (minBound :: Int16)
    i8min  = fromIntegral (minBound :: Int8)