3 ms·

Agreed. This is just like when I tried to grok monads. So many articles trying to tell me how simple they are... yet still so many articles needed to explain it

• continuational 9y ago
  Monad is just an interface with these methods: pure :: a -> List a flatten :: List (List a) -> List a map :: (a -> b) -> List a -> List b The above types are for lists, but you can substitute your own type constructor for List. For lists, the implementation is as follows: pure x = [x] flatten [] = [] flatten (x:xs) = x ++ flatten xs map f [] = [] map f (x:xs) = f x : map f xs A flatMap method can be defined once for all monads: flatMap f m = flatten (map f m) This method is sometimes called "bind" and is written ">>=" in Haskell (where pure is also called "return" and flatten is also called "join"): m >>= f = flatMap f m The methods are related by the monad laws - you can look them up if you're interested, but they're not required to gain an intuition.