elm extensible records example

ext.elm

module Main exposing (..)

import Html exposing (Html, text)

type alias Named a = { a | name : String }

foo : Compound -> String
foo named = named.name ++ "!"

type alias Position r = { r |  x:Float }
type alias Velocity r = { r | vx:Float }
type alias Person r = { r | name:String }
type alias Compound = Person (Position (Velocity {}))

main : Html a
main =
  let compound = {x = 1.0, vx = 1.1, name = "pete"}
  in
    text ("hi, " ++ foo compound)