Concepts

Shpadoinkle is a new way to program user interfaces with Haskell.

The core idea here is to model user interfaces as functions with type:

view :: Model -> Html m Model

This lets you describe the view as a pure function predicated on the current application state. It also suggests that changes to application state are dictated by the view.

Here is a simple example that displays a counter:

view :: Int -> Html m Int
view model = (1)
  div []
  [ text $ pack $ show model (2)
  , button
    [ onClick (+ 1) ] (3)
    [ text "Increment" ]
  ]
1 The function receives the current application state (which is just an Int)
2 Shows the current state to the user in a text node
3 When the user clicks the <button> it is added to the model

That is it. If you can understand what is going on in the above example, you understand Shpadoinkle, it’s that simple. There is no dispatch, no payloads, no event types, no giant update function, no networks of state managers, no templating, no special HTML syntax, no magic attributes, no digest cycle, and nothing fancy going on.

In fact, the only part of Shpadoinkle that actually performs work is only about 12 lines of code.