MonoidSillyExample.scala

import cats.Monoid
import cats.syntax.monoid._

case class Order(products: List[String], topay: Double)

//This could be done with higher abstraction cats tools
implicit val orderMonoidInstance: Monoid[Order] = new Monoid[Order] { 
  def empty: Order = Order(Nil, 0.0)
  def combine(x: Order, y: Order): Order = Order(x.products ++ y.products, x.topay + y.topay)
} 

val orders =  Order("fp2016"::Nil, 20.0)::Order("bananas"::"apples"::Nil, 10.0)::Nil

orders.combineAll