type class exercise in Elm

TypeClassSim.elm

import Html exposing (text)


main =
  text (toString <| allTheSame equal [ obj1, obj2, obj3 ])
  
  
obj1 = { id = 1, name = "foo" }
obj2 = { id = 1, name = "bar" }
obj3 = { id = 1, name = "baz" }
  
  
equal a b =
  a.id == b.id
  
  
type alias Eq a = a -> a -> Bool

  
allTheSame : Eq a -> List a -> Bool
allTheSame eq list =
  case list of
    x :: y :: rest ->
      eq x y && allTheSame eq (y :: rest)
      
    _ ->
      True