From a606d9d7988009df7dfaf44f8351dcada09485a5 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@github.com>
Date: Wed, 14 Oct 2015 10:03:42 -0400
Subject: [PATCH] Implement `duplicate` on Cofree.

---
 prototype/Doubt/Cofree.swift | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/prototype/Doubt/Cofree.swift b/prototype/Doubt/Cofree.swift
index 9c70a67dd..33288bc9b 100644
--- a/prototype/Doubt/Cofree.swift
+++ b/prototype/Doubt/Cofree.swift
@@ -25,4 +25,8 @@ extension Cofree {
 	public func extend<Other>(transform: Cofree -> Other) -> Cofree<A, Other> {
 		return .Unroll(transform(self), unwrap.map { $0.extend(transform) })
 	}
+
+	public var duplicate: Cofree<A, Cofree<A, B>> {
+		return .Unroll(self, unwrap.map { $0.duplicate })
+	}
 }