{-
Unzip an `Optional` value into two separate `Optional` values

Examples:

```
./unzip Text Bool (Some { _1 = "ABC", _2 = True  })
= { _1 = Some "ABC", _2 = Some True }

./unzip Text Bool (None { _1 : Text, _2 : Bool })
= { _1 = None Text, _2 = None Bool }
```
-}
    let unzip
        :   ∀(a : Type)
          → ∀(b : Type)
          → Optional { _1 : a, _2 : b }
          → { _1 : Optional a, _2 : Optional b }
        =   λ(a : Type)
          → λ(b : Type)
          → λ(xs : Optional { _1 : a, _2 : b })
          → { _1 =
                Optional/fold
                { _1 : a, _2 : b }
                xs
                (Optional a)
                (λ(x : { _1 : a, _2 : b }) → Some x._1)
                (None a)
            , _2 =
                Optional/fold
                { _1 : a, _2 : b }
                xs
                (Optional b)
                (λ(x : { _1 : a, _2 : b }) → Some x._2)
                (None b)
            }

in  unzip