type NonEmpty<T> = [T, ...T[]]
newtype EvenGreaterThan100 = EvenGreaterThan100 Natural
evenGreaterThan100ToInteger :: EvenGreaterThan100 -> Integer
evenGreaterThan100ToInteger (EvenGreaterThan100 n) = (toInteger n * 2) + 102
integerToEvenGreaterThan100 :: Integer -> Maybe EvenGreaterThan100
integerToEvenGreaterThan100 n
| n < 100 = Nothing
| otherwise = case n `quotRem` 2 of
(q, 0) -> Just (EvenGreaterThan100 q)
(_, _) -> Nothing
val xs[A]: ArrayBuffer[A] = ArrayBuffer[A]()
val bools: ArrayBuffer[Bool] = xs[Bool]
bools += true
val ints: ArrayBuffer[Int] = xs[Int]
ints.last
def xs[A](): ArrayBuffer[A] = ArrayBuffer[A]()
newArrayBuffer :: forall a. IO (ArrayBuffer a)
xs :: forall a. ArrayBuffer a
xs :: forall a. ArrayBuffer a
xs = unsafePerformIO (newArrayBuffer @a)
mapM :: Monad m => (a -> m b) -> [a] -> m [b]
mapM f [] = return []
mapM f (x:xs) = (:) <$> f x <*> mapM f xs
fun map f [] = []
| map f (x :: xs) = op:: (f x) (map f xs)
When I wrote this blog post, I used a very simple datatype because it was an extraordinarily simple example, but given many of the comments here, it seems it may have been too simple (and thus too contrived). It is only an illustration; don’t read into it too much.