From e6f439cb43ee51b13ed4d29ec84ac5450556b163 Mon Sep 17 00:00:00 2001
From: Johannes Stoelp <johannes.stoelp@gmail.com>
Date: Wed, 24 Aug 2022 18:09:52 +0200
Subject: c++: add any_of meta fn example

---
 src/development/c++/meta3.cc | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 src/development/c++/meta3.cc

(limited to 'src/development/c++/meta3.cc')

diff --git a/src/development/c++/meta3.cc b/src/development/c++/meta3.cc
new file mode 100644
index 0000000..5dce54a
--- /dev/null
+++ b/src/development/c++/meta3.cc
@@ -0,0 +1,22 @@
+// Copyright (C) 2022 johannst
+
+#include <type_traits>
+
+template<typename T, typename... U>
+struct any_of : std::false_type {};
+
+// Found our type T in the list of types U.
+template<typename T, typename... U>
+struct any_of<T, T, U...> : std::true_type {};
+
+// Pop off the first element in the list of types U,
+// since it didn't match our type T.
+template<typename T, typename U0, typename... U>
+struct any_of<T, U0, U...> : any_of<T, U...> {};
+
+// Convenience template variable to invoke meta function.
+template<typename T, typename... U>
+constexpr bool any_of_v = any_of<T, U...>::value;
+
+static_assert(any_of_v<int, char, bool, int>, "");
+static_assert(!any_of_v<int, char, bool, float>, "");
-- 
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