behavior.elm

import Task exposing (Task)

type Never = Never Never

type Behavior a = Behavior (a -> Task Never (Behavior a))


contramap : (b -> a) -> Behavior a -> Behavior b
contramap f (Behavior g) = 
  Behavior (\b -> Task.map (contramap f) (g (f b)))
  
  
divide : (c -> (a, b)) -> Behavior a -> Behavior b -> Behavior c
divide f (Behavior fa) (Behavior fb) =
  Behavior <| 
    \c ->
      case f c of 
        (a, b) ->
          fa a 
            `Task.andThen` \behaviorA -> fb b
            `Task.andThen` \behaviorB -> Task.succeed (divide f behaviorA behaviorB)
           
  
  
runBehavior : Behavior a -> List a -> Task Never ()
runBehavior (Behavior f) list = 
  case list of 
    [] ->
      Task.succeed ()
      
    x :: xs ->
      f x 
        `Task.andThen` \behavior -> runBehavior behavior xs