添加单位元委托Identity

Sanchime.Functional/Core/Extensions/Identity.cs

@@ -0,0 +1,12 @@
+using Sanchime.Functional.Core.Products;
+
+namespace Sanchime.Functional.Core.Extensions;
+
+public static class IdentityExtension
+{
+    public static Identity<R> Map<T, R>(this Identity<T> @this, Func<T, R> mapping)
+        => () => mapping(@this());
+
+    public static Identity<R> Bind<T, R>(this Identity<T> @this, Func<T, Identity<R>> binding)
+        => binding(@this()).Invoke();
+}

Sanchime.Functional/Core/Products/Identity.cs

@@ -0,0 +1,8 @@
+namespace Sanchime.Functional.Core.Products;
+
+/// <summary>
+/// 单位元
+/// </summary>
+/// <typeparam name="T"></typeparam>
+/// <returns></returns>
+public delegate T Identity<T>();