Created
January 3, 2012 12:00
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Scala Association Heterogeneous List (map with heterogeneous values)
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| // Association Heterogeneous List | |
| object AHListTest { | |
| object AHList { | |
| def apply[K]() = new AHNil[K]() | |
| } | |
| sealed trait AHList[K] { | |
| def get[V : Manifest](k: K): Option[V] = None | |
| def get[V : Manifest](k: K, default: V): V = get[V](k).getOrElse(default) | |
| def put[V : Manifest](k: K, v: V) = AHCons(k -> v, this) | |
| } | |
| final class AHNil[K] extends AHList[K] { | |
| def ::[V : Manifest](v : Tuple2[K, V]) = AHCons(v, this) | |
| } | |
| def AHNil[K] = new AHNil[K]() | |
| final case class AHCons[K, V : Manifest, T <: AHList[K]](head : Tuple2[K, V], tail : T) extends AHList[K] { | |
| def ::[V : Manifest](v : Tuple2[K, V]) = AHCons(v, this) | |
| override def get[L : Manifest](key: K): Option[L] = { | |
| if (head._1 == key && manifest[V] <:< manifest[L]) Some(head._2.asInstanceOf[L]) | |
| else tail.get[L](key) | |
| } | |
| } | |
| type ::[K, V, T <: AHList[K]] = AHCons[K, V, T] | |
| } | |
| /* | |
| scala> val list = ("age" -> 26) :: ("name" -> "Alois") :: AHNil[String] | |
| list: AHListTest.AHCons[String,Int,AHListTest.AHCons[String,java.lang.String,AHListTest.AHNil[String]]] = AHCons((age,26),AHCons((name,Alois),AHListTest$AHNil@2f0f94a0)) | |
| scala> list.head._2 | |
| res0: Int = 26 | |
| scala> list.tail.head._2 | |
| res1: java.lang.String = Alois | |
| */ | |
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