sbt/util/collection/PMap.scala

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/* sbt -- Simple Build Tool
* Copyright 2010 Mark Harrah
*/
package sbt
import Types._
trait PMap[K[_], V[_]] extends (K ~> V)
{
def apply[T](k: K[T]): V[T]
def get[T](k: K[T]): Option[V[T]]
def update[T](k: K[T], v: V[T]): Unit
def contains[T](k: K[T]): Boolean
def remove[T](k: K[T]): Option[V[T]]
def getOrUpdate[T](k: K[T], make: => V[T]): V[T]
}
object PMap
{
implicit def toFunction[K[_], V[_]](map: PMap[K,V]): K[_] => V[_] = k => map(k)
}
abstract class AbstractPMap[K[_], V[_]] extends PMap[K,V]
{
def apply[T](k: K[T]): V[T] = get(k).get
def contains[T](k: K[T]): Boolean = get(k).isDefined
}
import collection.mutable.Map
/** Only suitable for K that is invariant in its parameter.
* Option and List keys are not, for example, because None <:< Option[String] and None <: Option[Int].*/
class DelegatingPMap[K[_], V[_]](backing: Map[K[_], V[_]]) extends AbstractPMap[K,V]
{
def get[T](k: K[T]): Option[V[T]] = cast[T]( backing.get(k) )
def update[T](k: K[T], v: V[T]) { backing(k) = v }
def remove[T](k: K[T]) = cast( backing.remove(k) )
def getOrUpdate[T](k: K[T], make: => V[T]) = cast[T]( backing.getOrElseUpdate(k, make) )
private[this] def cast[T](v: V[_]): V[T] = v.asInstanceOf[V[T]]
private[this] def cast[T](o: Option[V[_]]): Option[V[T]] = o map cast[T]
override def toString = backing.toString
}