From 0d662ade08f088616b9533af1d19e3f3bc0ef854 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@github.com>
Date: Wed, 14 Oct 2015 09:43:23 -0400
Subject: [PATCH] Implement `extract` on `Cofree`.

---
 prototype/Doubt/Cofree.swift | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/prototype/Doubt/Cofree.swift b/prototype/Doubt/Cofree.swift
index 7e3378463..864ac8bd5 100644
--- a/prototype/Doubt/Cofree.swift
+++ b/prototype/Doubt/Cofree.swift
@@ -3,3 +3,15 @@
 public enum Cofree<B> {
 	case Unroll(B)
 }
+
+
+// MARK: - Comonad
+
+extension Cofree {
+	var extract: B {
+		switch self {
+		case let .Unroll(b):
+			return b
+		}
+	}
+}