formatDecimal i
    | i < 0     = minus Mon.<>
                  if i <= -128
                  then formatPositive (-(i `quot` 10)) Mon.<> digit (-(i `rem` 10))
                  else formatPositive (-i)
    | otherwise = formatPositive i

formatPositive = go
  where go n | n < 10    = digit n
             | otherwise = go (n `quot` 10) Mon.<> digit (n `rem` 10)

digit :: Integral a => a -> Builder
digit n = word8 $! i2w (fromIntegral n)

class F a where
  fb :: a -> Builder

newtype Fast a = Fast a

instance F a => ToField (Fast a) where
   toField (F a) = toStrict . toLazyByteString $ fb a

deriving via F Int64 instance ToField Int64