From 4cd07ae65a7cedb55c2d77366eb356e9b551f3bf Mon Sep 17 00:00:00 2001
From: Anairkoen Schno <aaron.cirr.com@gmail.com>
Date: Sat, 7 Dec 2019 23:44:26 -0600
Subject: [PATCH] Added own implementation of IEnumerable.Prepend

---
 IPA.Loader/IPA.Loader.csproj                 |  1 +
 IPA.Loader/Utilities/EnumerableExtensions.cs | 45 ++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 IPA.Loader/Utilities/EnumerableExtensions.cs

diff --git a/IPA.Loader/IPA.Loader.csproj b/IPA.Loader/IPA.Loader.csproj
index 9e0a7a0e..1785dc84 100644
--- a/IPA.Loader/IPA.Loader.csproj
+++ b/IPA.Loader/IPA.Loader.csproj
@@ -131,6 +131,7 @@
     <Compile Include="Utilities\BeatSaber.cs" />
     <Compile Include="Utilities\AlmostVersion.cs" />
     <Compile Include="Utilities\CriticalSection.cs" />
+    <Compile Include="Utilities\EnumerableExtensions.cs" />
     <Compile Include="Utilities\Ref.cs" />
     <Compile Include="Utilities\ReflectionUtil.cs" />
     <Compile Include="Loader\Composite\CompositeIPAPlugin.cs" />
diff --git a/IPA.Loader/Utilities/EnumerableExtensions.cs b/IPA.Loader/Utilities/EnumerableExtensions.cs
new file mode 100644
index 00000000..61ba93a4
--- /dev/null
+++ b/IPA.Loader/Utilities/EnumerableExtensions.cs
@@ -0,0 +1,45 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace IPA.Utilities
+{
+    /// <summary>
+    /// Extensions for <see cref="IEnumerable{T}"/> that don't currently exist in <c>System.Linq</c>.
+    /// </summary>
+    public static class EnumerableExtensions
+    {
+        /// <summary>
+        /// Adds a value to the beginning of the sequence.
+        /// </summary>
+        /// <typeparam name="T">the type of the elements of <paramref name="seq"/></typeparam>
+        /// <param name="seq">a sequence of values</param>
+        /// <param name="prep">the value to prepend to <paramref name="seq"/></param>
+        /// <returns>a new sequence beginning with <paramref name="prep"/></returns>
+        public static IEnumerable<T> Prepend<T>(this IEnumerable<T> seq, T prep)
+            => new PrependEnumerable<T>(seq, prep);
+
+        private sealed class PrependEnumerable<T> : IEnumerable<T>
+        {
+            private readonly IEnumerable<T> rest;
+            private readonly T first;
+
+            public PrependEnumerable(IEnumerable<T> rest, T first)
+            {
+                this.rest = rest;
+                this.first = first;
+            }
+
+            public IEnumerator<T> GetEnumerator()
+            {
+                yield return first;
+                foreach (var v in rest) yield return v;
+            }
+
+            IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+        }
+    }
+}