21 lines
482 B
Scala
21 lines
482 B
Scala
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sealed abstract class List[+a]
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private case object Nil extends List[Nothing]
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private final case class Cons[+a](head: a, tail: List[a])
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extends List[a]
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object List {
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def unapply[a](xs: List[a]): Option[(a, List[a])] = xs match {
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case Nil => None
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case Cons(x, xs) => Some(x, xs)
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}
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def unapply[a](xs: List[a]): Option[Null] = xs match {
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case Nil => Some(null)
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case Cons(_, _) => None
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}
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def foo[a](xs: List[a]) = xs match {
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case List(x, xs) => 7
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}
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}
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