Triangle.scala

import scala.util.Try

case class Triangle(
  opposite: Float,
  adjacent: Float,
  hypotenuse: Float
) {
  require(
    opposite + adjacent > hypotenuse &&
    adjacent + hypotenuse > opposite &&
    opposite + hypotenuse > adjacent,
    "Triangle's law should be satisfied")
  
  require(
    opposite*opposite + adjacent*adjacent == hypotenuse*hypotenuse,
    "Pythagoras law should be satisfied")
  
  def sin(): Option[Float] = {
    hypotenuse match {
      case 0 => None
      case h => Some(opposite/h)
    }
  }
  
  def cos(): Option[Float] = {
    hypotenuse match {
      case 0 => None
      case h => Some(adjacent/h)
    }
  }
  
  def tan(): Option[Float] = for {
    s <- sin
    c <- cos
  } yield s/c
}


val good = Try(Triangle(3, 4, 5)).toOption
// good: Option[Triangle] = Some(Triangle(3.0,4.0,5.0))

println(good.flatMap(_.cos))
// Some(0.8)

println(good.flatMap(_.tan))
// Some(0.75)

val bad = Try(Triangle(4, 5, 5)).toOption
// bad: Option[Triangle] = None

println(bad.flatMap(_.cos))
// None

println(bad.flatMap(_.tan))
// None