groups as an exampleWhy not go all the way and teach functors and applicatives before monads? Then the student can see that monads are just a small addition built on top of the other two. Functors, in particular, are very easy to grasp despite their intimidating name. They just generalize map over arbitrary data structures:
l_double : List Int -> List Int
l_double xs = map (* 2) xs
f_double : Functor f => f Int -> f Int
f_double xs = map (* 2) xs
Applicatives are a little bit trickier but once you get them, there's only a tiny jump to get to monads. Taught this way, people will realize that they don't need the full power of monads for everything. Then, when people learn about idiom brackets [1], they start to get really excited! Instead of writing this:
m_add : Maybe Int -> Maybe Int -> Maybe Int
m_add x y = case x of
Nothing => Nothing
Just x' => case y of
Nothing => Nothing
Just y' => Just (x' + y')
You can write this:
m_add' : Maybe Int -> Maybe Int -> Maybe Int
m_add' x y = [| x + y |]
Much better!
[1] http://docs.idris-lang.org/en/latest/tutorial/interfaces.htm...
Why not go all the way and teach functors and applicatives before monads? Then the student can see that monads are just a small addition built on top of the other two. Functors, in particular, are very easy to grasp despite their intimidating name. They just generalize map over arbitrary data structures:
Applicatives are a little bit trickier but once you get them, there's only a tiny jump to get to monads. Taught this way, people will realize that they don't need the full power of monads for everything. Then, when people learn about idiom brackets [1], they start to get really excited! Instead of writing this: You can write this: Much better![1] http://docs.idris-lang.org/en/latest/tutorial/interfaces.htm...