gistfile1.scala

trait Query { def i: Int }

// A Query and a Query Decorator
case class SimpleQuery(val i: Int) extends Query
case class TimingOutQuery(timeout: Int)(query: Query) extends Query { def i = query.i }

// Factories
type QueryFactory = Int => Query

// A thing that needs to make Queries
class QueryEvaluator(Query: QueryFactory)(k: Int) {
  def apply() = Query(1 + k).i
}

// A specific set of decorators:
val myQueryFactory = SimpleQuery andThen TimingOutQuery(1) // andThen StatsColletingQuery(...)

// Using it
val queryEvaluator = new QueryEvaluator(myQueryFactory)(1)
println(queryEvaluator())