From dd8d58a9c06a44272ca83d0e38a5157f1f1a6120 Mon Sep 17 00:00:00 2001
From: Mark Harrah <dmharrah@gmail.com>
Date: Fri, 27 Aug 2010 19:17:03 -0400
Subject: [PATCH] cross-configurations

---
 util/collection/Attributes.scala | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/util/collection/Attributes.scala b/util/collection/Attributes.scala
index 231cda300..488142ad7 100644
--- a/util/collection/Attributes.scala
+++ b/util/collection/Attributes.scala
@@ -8,10 +8,12 @@ import Types._
 // T must be invariant to work properly.
 //  Because it is sealed and the only instances go through make,
 //  a single AttributeKey instance cannot conform to AttributeKey[T] for different Ts
-sealed trait AttributeKey[T]
+sealed trait AttributeKey[T] {
+	def label: String
+}
 object AttributeKey
 {
-	def make[T]: AttributeKey[T] = new AttributeKey[T] {}
+	def apply[T](name: String): AttributeKey[T] = new AttributeKey[T] { def label = name }
 }
 
 trait AttributeMap
@@ -20,15 +22,35 @@ trait AttributeMap
 	def get[T](k: AttributeKey[T]): Option[T]
 	def contains[T](k: AttributeKey[T]): Boolean
 	def put[T](k: AttributeKey[T], value: T): AttributeMap
+	def keys: Iterable[AttributeKey[_]]
+	def ++(o: AttributeMap): AttributeMap
+	def entries: Iterable[AttributeEntry[_]]
+	def isEmpty: Boolean
 }
 object AttributeMap
 {
-	def empty: AttributeMap = new BasicAttributeMap(Map.empty)
+	val empty: AttributeMap = new BasicAttributeMap(Map.empty)
 }
-private class BasicAttributeMap(backing: Map[AttributeKey[_], Any]) extends AttributeMap
+private class BasicAttributeMap(private val backing: Map[AttributeKey[_], Any]) extends AttributeMap
 {
+	def isEmpty: Boolean = backing.isEmpty
 	def apply[T](k: AttributeKey[T]) = backing(k).asInstanceOf[T]
 	def get[T](k: AttributeKey[T]) = backing.get(k).asInstanceOf[Option[T]]
 	def contains[T](k: AttributeKey[T]) = backing.contains(k)
 	def put[T](k: AttributeKey[T], value: T): AttributeMap = new BasicAttributeMap( backing.updated(k, value) )
+	def keys: Iterable[AttributeKey[_]] = backing.keys
+	def ++(o: AttributeMap): AttributeMap =
+		o match {
+			case bam: BasicAttributeMap => new BasicAttributeMap(backing ++ bam.backing)
+			case _ => o ++ this
+		}
+	def entries: Iterable[AttributeEntry[_]] =
+		for( (k: AttributeKey[kt], v) <- backing) yield AttributeEntry(k, v.asInstanceOf[kt])
+	override def toString = entries.mkString("(", ", ", ")")
+}
+
+// type inference required less generality
+final case class AttributeEntry[T](a: AttributeKey[T], b: T)
+{
+	override def toString = a.label + ": " + b
 }
\ No newline at end of file