From 26f0ea419df4dfde06cc2ecc4aa320d935bf6702 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@github.com>
Date: Wed, 14 Oct 2015 10:00:16 -0400
Subject: [PATCH] Implement `extend` 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 8e9b89325..afe4558dc 100644
--- a/prototype/Doubt/Cofree.swift
+++ b/prototype/Doubt/Cofree.swift
@@ -21,4 +21,8 @@ extension Cofree {
 			return b
 		}
 	}
+
+	func extend<Other>(transform: Cofree -> Other) -> Cofree<A, Other> {
+		return .Unroll(transform(self), unwrap.map { $0.extend(transform) })
+	}
 }