Scala compose monadic type

compose.scala

implicit class OptionK[A, B](f: (A) => Option[B]) {
  def composed[C](g: B => Option[C]): (A) => Option[C] = (x: A) => f(x).flatMap(g)
}

val strToInt:(String) => Option[Int] = s => if(s.matches("-?[\\d]+")) Some(s.toInt) else None

val realSqrt:(Int) => Option[Double] = x => if(x > 0) Some(Math.sqrt(x)) else None

val strToSqrt = strToInt composed realSqrt

strToSqrt("9") //Some(3.0)
strToSqrt("-9") //None
strToSqrt("meh") //None