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final class Opt[+A >: Null](val value: A) extends AnyVal {
def get: A = value
def isEmpty = value == null
def isDefined = !isEmpty
}
object Opt {
final val None = new Opt[Null](null)
def apply[A >: Null](value: A): Opt[A] = if (value == null) None else new Opt[A](value)
}
object ValueOpt {
// public java.lang.String unapply(java.lang.Object);
// 0: aload_1
// 1: instanceof #16 // class java/lang/String
// 4: ifeq 21
// 7: getstatic #21 // Field Opt$.MODULE$:LOpt$;
// 10: astore_2
// 11: ldc #23 // String String
// 13: checkcast #16 // class java/lang/String
// 16: astore 5
// 18: goto 71
// 21: aload_1
// 22: instanceof #25 // class scala/collection/immutable/List
// 25: ifeq 42
// 28: getstatic #21 // Field Opt$.MODULE$:LOpt$;
// 31: astore_3
// 32: ldc #27 // String List
// 34: checkcast #16 // class java/lang/String
// 37: astore 5
// 39: goto 71
// 42: aload_1
// 43: instanceof #29 // class java/lang/Integer
// 46: ifeq 64
// 49: getstatic #21 // Field Opt$.MODULE$:LOpt$;
// 52: astore 4
// 54: ldc #31 // String Int
// 56: checkcast #16 // class java/lang/String
// 59: astore 5
// 61: goto 71
// 64: getstatic #21 // Field Opt$.MODULE$:LOpt$;
// 67: pop
// 68: aconst_null
// 69: astore 5
// 71: aload 5
// 73: areturn
def unapply(x: Any): Opt[String] = x match {
case _: String => Opt("String")
case _: List[_] => Opt("List")
case _: Int => Opt("Int")
case _ => Opt.None
}
}
object RegularOpt {
// public scala.Option<java.lang.String> unapply(java.lang.Object);
// 0: aload_1
// 1: instanceof #16 // class java/lang/String
// 4: ifeq 20
// 7: new #18 // class scala/Some
// 10: dup
// 11: ldc #20 // String String
// 13: invokespecial #23 // Method scala/Some."<init>":(Ljava/lang/Object;)V
// 16: astore_2
// 17: goto 64
// 20: aload_1
// 21: instanceof #25 // class scala/collection/immutable/List
// 24: ifeq 40
// 27: new #18 // class scala/Some
// 30: dup
// 31: ldc #27 // String List
// 33: invokespecial #23 // Method scala/Some."<init>":(Ljava/lang/Object;)V
// 36: astore_2
// 37: goto 64
// 40: aload_1
// 41: instanceof #29 // class java/lang/Integer
// 44: ifeq 60
// 47: new #18 // class scala/Some
// 50: dup
// 51: ldc #31 // String Int
// 53: invokespecial #23 // Method scala/Some."<init>":(Ljava/lang/Object;)V
// 56: astore_2
// 57: goto 64
// 60: getstatic #36 // Field scala/None$.MODULE$:Lscala/None$;
// 63: astore_2
// 64: aload_2
// 65: areturn
def unapply(x: Any): Option[String] = x match {
case _: String => Some("String")
case _: List[_] => Some("List")
case _: Int => Some("Int")
case _ => None
}
}
object Test {
def f(x: Any) = x match {
case ValueOpt(s) => s
case _ => "Something else"
}
def g(x: Any) = x match {
case RegularOpt(s) => s
case _ => "Something else"
}
val xs = List("abc", Nil, 5, Test)
def main(args: Array[String]): Unit = {
xs map f foreach println
xs map g foreach println
}
}
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