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  1. trait CanQuantify[Q <: Quantity[T], T] {
  2.   def apply(value: T): Q
  3. }
  4.  
  5. trait Quantity[T] {
  6.   type Self <: Quantity[T]
  7.  
  8.   def value: T
  9.  
  10.   def +(that: Quantity[T])(implicit q: CanQuantify[Self, T], num: Numeric[T]) = {
  11.   	import num._
  12.   	q(value + that.value)
  13.   }
  14.  
  15.   def *[R <: Quantity[T]](that: R)(implicit num: Numeric[T]) = {
  16.   	import num._
  17.   	Times[T, Self, R](value * that.value)
  18.   }
  19.  
  20.   def /[R <: Quantity[T]](that: R)(implicit num: Fractional[T]) = {
  21.   	import num._
  22.     Per[T, Self, R](value / that.value)
  23.   }
  24. }
  25.  
  26. case class Times[T, Q <: Quantity[T], R <: Quantity[T]](value: T) extends Quantity[T] {
  27.   override type Self = Per[T, Q, R]
  28.  
  29.   def /(that: R)(implicit q: CanQuantify[Q, T], num: Fractional[T]) = {
  30.   	import num._
  31.   	q(value / that.value)
  32.   }
  33. }
  34.  
  35. case class Per[T, Q <: Quantity[T], R <: Quantity[T]](value: T) extends Quantity[T] {
  36.   override type Self = Per[T, Q, R]
  37.  
  38.   def *(that: R)(implicit q: CanQuantify[Q, T], num: Numeric[T]) = {
  39.   	import num._
  40.   	q(value * that.value)
  41.   }
  42. }
  43.  
  44. case class ProductCount(value: Double) extends Quantity[Double] {
  45.   override type Self = ProductCount
  46. }
  47.  
  48. case class BoxCount(value: Double) extends Quantity[Double] {
  49.   override type Self = BoxCount
  50. }
  51.  
  52. object canQuantifies {
  53.   implicit val productCountCanQuantify = new CanQuantify[ProductCount, Double] {
  54.     override def apply(value: Double) = ProductCount(value)
  55.   }
  56.  
  57.   implicit val boxCountCanQuantify = new CanQuantify[BoxCount, Double] {
  58.     override def apply(value: Double) = BoxCount(value)
  59.   }
  60. }
  61. import canQuantifies._
  62.  
  63. object Main extends App {
  64.   val products = ProductCount(10.0)
  65.   val boxes = BoxCount(5.0)
  66.   var n = products / boxes
  67.   n = n * boxes / boxes
  68. }
Success #stdin #stdout 0.24s 381696KB
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https://ideone.com/CF8LGV
language:
Scala (scala 2.12.8)
created:
11 years ago
visibility:
public

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