From fac9e8bec1983fa9dff8f447fef106e427dfec26 Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Thu, 20 Jul 2023 17:02:05 +0200
Subject: c++: Renamed src to c++

---
 c++/core/templates.h | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 c++/core/templates.h

(limited to 'c++/core/templates.h')

diff --git a/c++/core/templates.h b/c++/core/templates.h
new file mode 100644
index 0000000..39befc1
--- /dev/null
+++ b/c++/core/templates.h
@@ -0,0 +1,76 @@
+#pragma once
+
+#include "string_literal.h"
+
+namespace saw {
+
+template <class T, class... TL> struct parameter_pack_index;
+
+template <class T, class... TL> struct parameter_pack_index<T, T, TL...> {
+	static constexpr size_t value = 0u;
+};
+
+template <class T, class TL0, class... TL>
+struct parameter_pack_index<T, TL0, TL...> {
+	static constexpr size_t value =
+		1u + parameter_pack_index<T, TL...>::value;
+};
+
+template <size_t N, class... T> struct parameter_pack_type {
+	static_assert(always_false<T...>, "Should've been caught by the specializations");
+};
+
+template <class TN, class... T> struct parameter_pack_type<0, TN, T...> {
+	using type = TN;
+};
+
+template <size_t N, class TN, class... T>
+struct parameter_pack_type<N, TN, T...> {
+	static_assert(sizeof...(T) > 0, "Exhausted parameters");
+	static_assert(N > 0, "Invalid number. Should've been caught");
+	using type = typename parameter_pack_type<N - 1, T...>::type;
+};
+/*
+ * Nightmare inducing compiler problems found here. Somehow non-type
+ * string_literals cannot be resolved as non-type primitive template values can.
+ * This is the workaround
+ */
+template <string_literal V, string_literal Key0, string_literal... Keys>
+struct parameter_key_pack_index_helper {
+	static constexpr size_t value =
+		(V == Key0)
+			? (0u)
+			: (1u + parameter_key_pack_index_helper<V, Keys...>::value);
+};
+
+template <string_literal V, string_literal Key0>
+struct parameter_key_pack_index_helper<V, Key0> {
+	static constexpr size_t value = (V == Key0) ? (0u) : (1u);
+};
+
+template <string_literal V, string_literal... Keys>
+struct parameter_key_pack_index {
+	static constexpr size_t value =
+		parameter_key_pack_index_helper<V, Keys...>::value;
+	static_assert(value < sizeof...(Keys),
+				  "Provided string_literal doesn't exist in searched list");
+};
+
+template <size_t i, size_t s, string_literal Key0, string_literal... Keys>
+struct parameter_key_pack_type_helper {
+	static constexpr string_literal literal = parameter_key_pack_type_helper<i, s+1, Keys...>::literal;
+};
+
+template <size_t i, string_literal Key0, string_literal... Keys>
+struct parameter_key_pack_type_helper<i, i, Key0, Keys...> {
+	static constexpr string_literal literal = Key0;
+};
+
+template <size_t i, string_literal... Keys>
+struct parameter_key_pack_type {
+	static constexpr string_literal literal = parameter_key_pack_type_helper<i, 0, Keys...>::literal;
+
+	static_assert(i < sizeof...(Keys), "Provided index is too large in list");
+};
+
+}
-- 
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