update.elm

update : Action -> Model -> Model
update action model =
  case action of
    Toggle seatToToggle ->
      let
        updateSeat seatFromModel =
          if seatFromModel.seatNo == seatToToggle.seatNo then
            -- Not working, compiler expects `=`
            { seatFromModel | occupied <- not seatFromModel.occupied }
            
            -- Works
            { seatFromModel | occupied = not seatFromModel.occupied }
          else seatFromModel
      in
        List.map updateSeat model