Imported Upstream version 5.0.0.42

Former-commit-id: fd56571888259555122d8a0f58c68838229cea2b

external/linker/cecil/rocks/Mono.Cecil.Rocks/Functional.cs

@@ -0,0 +1,41 @@
+//
+// Author:
+//   Jb Evain (jbevain@gmail.com)
+//
+// Copyright (c) 2008 - 2015 Jb Evain
+// Copyright (c) 2008 - 2011 Novell, Inc.
+//
+// Licensed under the MIT/X11 license.
+//
+
+using System;
+using System.Collections.Generic;
+
+namespace Mono.Cecil.Rocks {
+
+	static class Functional {
+
+		public static System.Func<A, R> Y<A, R> (System.Func<System.Func<A, R>, System.Func<A, R>> f)
+		{
+			System.Func<A, R> g = null;
+			g = f (a => g (a));
+			return g;
+		}
+
+		public static IEnumerable<TSource> Prepend<TSource> (this IEnumerable<TSource> source, TSource element)
+		{
+			if (source == null)
+				throw new ArgumentNullException ("source");
+
+			return PrependIterator (source, element);
+		}
+
+		static IEnumerable<TSource> PrependIterator<TSource> (IEnumerable<TSource> source, TSource element)
+		{
+			yield return element;
+
+			foreach (var item in source)
+				yield return item;
+		}
+	}
+}