From b3c0e92d2afed0e47e4783446345e8a7f062a941 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@github.com>
Date: Thu, 17 Sep 2015 14:14:01 -0400
Subject: [PATCH] Stream concatenation.

---
 prototype/Doubt/Stream.swift | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/prototype/Doubt/Stream.swift b/prototype/Doubt/Stream.swift
index a2db8b054..d81142b05 100644
--- a/prototype/Doubt/Stream.swift
+++ b/prototype/Doubt/Stream.swift
@@ -41,6 +41,16 @@ public enum Stream<A>: NilLiteralConvertible, SequenceType {
 	}
 
 
+	public func concat(other: Stream) -> Stream {
+		switch self {
+		case .Nil:
+			return other
+		case let .Cons(first, rest):
+			return .Cons(first, rest.map { $0.concat(other) })
+		}
+	}
+
+
 	public init(nilLiteral: ()) {
 		self = .Nil
 	}