From 39759805ac98b0291852c0551ad3678614ed6ce8 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Mon, 9 Sep 2019 07:37:37 +1000
Subject: [PATCH] functor: add the identity functor

---
 functor.hpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/functor.hpp b/functor.hpp
index 9b0e4f85..4900d604 100644
--- a/functor.hpp
+++ b/functor.hpp
@@ -13,6 +13,20 @@
 
 
 namespace cruft::functor {
+    /// Returns the supplied argument unchanged
+    ///
+    /// CXX#20: Revisit when C++20 support is available. This is just a
+    /// trivial implementation of std::identity.
+    struct identity {
+        template <typename ValueT>
+        ValueT&&
+        operator() (ValueT &&val)
+        {
+            return std::forward<ValueT> (val);
+        }
+    };
+
+
     /// A trivial functor that wraps std::begin without any static typing.
     struct begin {
         template <typename valuet>