Well, in a sense other languages opt-in to TM code by interfacing with a relational database. Similar to how in Haskell you put TVar in front of the relevant b

Well, in a sense other languages opt-in to TM code by interfacing with a relational database. Similar to how in Haskell you put TVar in front of the relevant bits to opt-in. In Haskell it's just more economic and better integrated with the rest of the language and its typesystem.