Scala functional programming gymnastics

Question

I am trying to do the following in as little code as possible and as functionally as possible:

def restrict(floor : Option[Double], cap : Option[Double], amt : D         


        

Answer 1

I'm adding another answer which was inspired by both retronym and Debilski - basically it amounts to converting the cap and floor to functions (Double => Double, if they are present) and then folding the identity function through them with composition:

def restrict(floor: Option[Double], cap: Option[Double], amt: Double) = {
  (identity[Double] _ /: List(floor.map(f => (_: Double) max f), cap.map(c => (_: Double) min c)).flatten){ _ andThen _ }(amt)
}