Their definitions of OOP and FP are rather restrictive - it's basically FP = ADTs (data) and OOP = interfaces (codata). Many modern languages support both (e.g.

Their definitions of OOP and FP are rather restrictive - it's basically FP = ADTs (data) and OOP = interfaces (codata). Many modern languages support both (e.g. Haskell has typeclasses, Java has records and sealed interfaces).