Memo does not need the evaluated label.

prototype/Doubt/Memo.swift

@@ -3,7 +3,7 @@ public struct Memo<A> {
 		self.init(.Unevaluated(unevaluted))
 	}
 
-	public init(evaluated: A) {
+	public init(_ evaluated: A) {
 		self.init(.Evaluated(evaluated))
 	}
 

prototype/Doubt/Stream.swift

@@ -32,7 +32,7 @@ public enum Stream<A>: NilLiteralConvertible, SequenceType {
 	}
 
 	public var rest: Memo<Stream> {
-		return analysis(ifCons: { $1 }, ifNil: { Memo(evaluated: .Nil) })
+		return analysis(ifCons: { $1 }, ifNil: { Memo(.Nil) })
 	}
 
 	public var isEmpty: Bool {
@@ -59,7 +59,7 @@ public enum Stream<A>: NilLiteralConvertible, SequenceType {
 	}
 
 	public func concat(other: Stream) -> Stream {
-		return concat(Memo(evaluated: other))
+		return concat(Memo(other))
 	}
 
 
@@ -76,7 +76,7 @@ public enum Stream<A>: NilLiteralConvertible, SequenceType {
 
 
 	public func generate() -> AnyGenerator<A> {
-		var current = Memo(evaluated: self)
+		var current = Memo(self)
 		return anyGenerator {
 			let next = current.value.first
 			current = current.value.rest

prototype/Doubt/Vertex.swift

@@ -8,7 +8,7 @@ public enum Vertex<Element> {
 		case let .XY(_, xs, _):
 			return xs
 		case .End:
-			return Memo(evaluated: .End)
+			return Memo(.End)
 		}
 	}
 
@@ -17,14 +17,14 @@ public enum Vertex<Element> {
 		case let .XY(_, _, ys):
 			return ys
 		case .End:
-			return Memo(evaluated: .End)
+			return Memo(.End)
 		}
 	}
 
 	public var diagonal: Memo<Vertex> {
 		return right.flatMap { $0.down }
 	}
-	
+
 
 	public init<A, B>(rows: Stream<A>, columns: Stream<B>, combine: (A, B) -> Element) {
 		self = columns