Prelude> :t 11111111111111111111111 11111111111111111111111 :: Num a => a Prelude> :t (length []) (length []) :: Int Prelude> 111111111111111111

Prelude> :t 11111111111111111111111 11111111111111111111111 :: Num a => a Prelude> :t (length []) (length []) :: Int Prelude> 11111111111111111111111111111 - (length []) 1729917383 Prelude> 1111111111111111111111111111 - 0 1111111111111111111111111111 Prelude> 1111111111111111111111111111 - fromIntegral (length []) 1111111111111111111111111111 Prelude> 11111111111111111111111111111 :: Int 1729917383 "Int" is the machine-length integer type. "Integer" is the unbounded, but slower integer type ("bigint" in other languages). In Prelude, "length" always returns an Int, assuming that the length of a list will never be bigger than 232. Haskell interprets numeric literals as the typeclass (Num a => a), meaning any member of the typeclass Num can be constructed using these literals. Int is one such type, and causes wraparound when it constructs an instance using the typeclass.