addressmusings.elm

import Task exposing (Task, succeed)

type Never = Never Never

type alias Address e = e -> Task Never ()

forwardTo : Address a -> (b -> a) -> Address b
forwardTo address f b = 
  address (f b)
  
type alias Loopback a b = Address a -> Address b


map : (a -> b) -> Loopback a x -> Loopback b x
map f loopA address x = 
  loopA (forwardTo address f) x
  
reroute : (b -> Maybe a) -> Loopback x a -> Loopback x b
reroute f loopA address b = 
  case f b of 
    Nothing ->
      succeed ()
      
    Just a ->
      loopA address a
  
  
dimap : (a -> b) -> (d -> Maybe c) -> Loopback a c -> Loopback b d
dimap f g = 
  map f >> reroute g

  
type ListAction a 
  = ChildAction Int a
  
    
  
list : Loopback action effect -> Loopback (ListAction action) (ListAction effect)
list loopback address (ChildAction n effect) = 
  loopback (forwardTo address (ChildAction n)) effect
 
 
 
  
type Json
  = String String
  | Int Int
  | Float Float
  | List (List Json)
  | Object String Json
  

getInt : Json -> Maybe Int
getInt json = 
  case json of 
    Int n -> Just n
    _ -> Nothing

  
int : Loopback Int Int -> Loopback Json Json
int = 
  dimap Int getInt