Scala example source code file (existentials.scala)

This example Scala source code file (existentials.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

a, any, c, c, cell, cell, counter, counter, float, int, option, t, t, u

The Scala existentials.scala source code

class Foo {
  class Line {
    case class Cell[T](var x: T)
    def f[T](x: Any): Cell[t1] forSome { type t1 } = x match { case y: Cell[t] => y }
    
    var x: Cell[T] forSome { type T } = new Cell(1)
    println({ x = new Cell("abc"); x })
  }
}

class FooW {
  class Line {
    case class Cell[T](var x: T)
    def f[T](x: Any): Cell[ _ ] = x match { case y: Cell[t] => y }
    
    var x: Cell[_] = new Cell(1)
    println({ x = new Cell("abc"); x })
  }
}

trait Counter[T] {
   def newCounter: T
   def get(i: T): Int
   def inc(i: T): T
}

case class C[T](x: T)

object LUB {
  def x = C(1)
  def y = C("abc")
  var coinflip: Boolean = _
  def z = if (coinflip) x else y
  def zz: C[_1] forSome { type _1 >: Int with java.lang.String } = z
  def zzs: C[_ >: Int with java.lang.String] = z
}

object Bug1189 {
  case class Cell[T](x: T)
  type U = Cell[T1] forSome { type T1 }
  def f(x: Any): U = x match { case y: Cell[_] => y }

  var x: U = Cell(1)
  println(x)

  println(f(x))

  x = Cell("abc")
  println(x)
  println(f(x))
}

object Test extends App {

  val x = { class I; class J; (new C(new I), new C(new J)) }
  val y: (C[X], C[Y]) forSome { type X; type Y } = x

   def foo(x : Counter[T] { def name : String } forSome { type T }) = x match {
     case ctr: Counter[t] =>
       val c = ctr.newCounter
       println(ctr.name+" "+ctr.get(ctr.inc(ctr.inc(c))))
     case _ =>
   }

   def fooW(x : Counter[T] { def name : String } forSome { type T }) = x match {
     case ctr: Counter[t] =>
       val c = ctr.newCounter
       println(ctr.name+" "+ctr.get(ctr.inc(ctr.inc(c))))
     case _ =>
   }

   val ci = new Counter[Int] {
     def newCounter = 0
     def get(i: Int) = i
     def inc(i: Int) = i+1
     def name = "Int"
   }

   val cf = new Counter[Float] {
     def newCounter = 0
     def get(i: Float) = i.intValue
     def inc(i: Float) = i+1
     def name = "Float"
   }

   var ex: Counter[T] forSome { type T } = _
   ex = ci
   ex = cf

   var exW: Counter[_] = _
   ex = ci
   ex = cf

   foo(ci)
   foo(cf)
   fooW(ci)
   fooW(cf)
   val foo = new Foo
   new foo.Line
   val fooW = new FooW
   new fooW.Line
}

trait FooBar[ A <: Option[_]] { def foo: A }
trait SubFooBar[B <: Option[_]] extends FooBar[B]

object Test1 {

  var pc: List[Product with (Counter[T] forSome { type T })] = List()
  def f() = pc
  pc = f()
}