The number of variables doesn't matter, as long as they are the same type is the part that matters. <T, E> can be thought of as a pair, tuple, cartesian produc

The number of variables doesn't matter, as long as they are the same type is the part that matters. <T, E> can be thought of as a pair, tuple, cartesian product. Likewise you can expand it to as many values as you want. If type C is just (T, E) then it is really just Result<C> at that point. The first T can vary but as long as everything after that is fixed to the same type, you can have as many variables/types as you want and it will still be monadic.