From 84921fffa7aa6efd80f694ec295d4562c326fabc Mon Sep 17 00:00:00 2001
From: Brett Laptop <tri11paragon@tpgc.me>
Date: Wed, 23 Apr 2025 15:04:37 -0400
Subject: [PATCH] tuples!

---
 CMakeLists.txt                   |   2 +-
 include/blt/meta/function.h      | 152 +++++++++++++++++++++++++++++++
 include/blt/meta/passthrough.h   |  31 +++++++
 include/blt/meta/tuple_filters.h |  80 ++++++++++++++++
 include/blt/std/variant.h        |  65 ++++++-------
 tests/variant_tests.cpp          |  24 ++---
 6 files changed, 306 insertions(+), 48 deletions(-)
 create mode 100644 include/blt/meta/function.h
 create mode 100644 include/blt/meta/passthrough.h
 create mode 100644 include/blt/meta/tuple_filters.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4c812ac..1a2601a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.20)
 include(cmake/color.cmake)
-set(BLT_VERSION 5.4.8)
+set(BLT_VERSION 5.4.9)
 
 set(BLT_TARGET BLT)
 
diff --git a/include/blt/meta/function.h b/include/blt/meta/function.h
new file mode 100644
index 0000000..a64ebaa
--- /dev/null
+++ b/include/blt/meta/function.h
@@ -0,0 +1,152 @@
+#pragma once
+/*
+ *  Copyright (C) 2024  Brett Terpstra
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef BLT_META_FUNCTION_H
+#define BLT_META_FUNCTION_H
+
+#include <functional>
+#include <tuple>
+
+namespace blt::meta
+{
+	struct std_function_tag
+	{};
+
+	struct function_ptr_tag
+	{};
+
+	struct lambda_tag
+	{};
+
+	struct member_function_ptr_tag
+	{};
+
+	template <typename Func>
+	struct function_like;
+
+	template <typename Return, typename... Args>
+	struct function_like<std::function<Return(Args...)>>
+	{
+		using return_type = Return;
+		using args_tuple = std::tuple<Args...>;
+		using tag = std_function_tag;
+	};
+
+	template <typename Return, typename... Args>
+	struct function_like<Return (*)(Args...)>
+	{
+		using return_type = Return;
+		using args_tuple = std::tuple<Args...>;
+		using tag = function_ptr_tag;
+	};
+
+	template <typename Return, typename... Args>
+	struct function_like<Return (*)(Args...) noexcept>
+	{
+		using return_type = Return;
+		using args_tuple = std::tuple<Args...>;
+		using tag = function_ptr_tag;
+	};
+
+	template <typename Return, typename Class, typename... Args>
+	struct function_like<Return (Class::*)(Args...)>
+	{
+		using return_type = Return;
+		using args_tuple = std::tuple<Args...>;
+		using tag = member_function_ptr_tag;
+		using class_type = Class;
+	};
+
+	template <typename Return, typename Class, typename... Args>
+	struct function_like<Return (Class::*)(Args...) const>
+	{
+		using return_type = Return;
+		using args_tuple = std::tuple<Args...>;
+		using tag = member_function_ptr_tag;
+		using class_type = Class;
+	};
+
+	template <typename Return, typename Class, typename... Args>
+	struct function_like<Return (Class::*)(Args...) noexcept>
+	{
+		using return_type = Return;
+		using args_tuple = std::tuple<Args...>;
+		using tag = member_function_ptr_tag;
+		using class_type = Class;
+	};
+
+	template <typename Return, typename Class, typename... Args>
+	struct function_like<Return (Class::*)(Args...) const noexcept>
+	{
+		using return_type = Return;
+		using args_tuple = std::tuple<Args...>;
+		using tag = member_function_ptr_tag;
+		using class_type = Class;
+	};
+
+	template <typename Func>
+	struct function_like
+	{
+	private:
+		template <typename>
+		struct lambda_traits
+		{};
+
+		template <typename Return, typename Class, typename... Args>
+		struct lambda_traits<Return (Class::*)(Args...) const>
+		{
+			using return_type = Return;
+			using args_tuple = std::tuple<Args...>;
+			using class_type = Class;
+		};
+
+		template <typename Return, typename Class, typename... Args>
+		struct lambda_traits<Return (Class::*)(Args...) noexcept>
+		{
+			using return_type = Return;
+			using args_tuple = std::tuple<Args...>;
+			using class_type = Class;
+		};
+
+		template <typename Return, typename Class, typename... Args>
+		struct lambda_traits<Return (Class::*)(Args...) const noexcept>
+		{
+			using return_type = Return;
+			using args_tuple = std::tuple<Args...>;
+			using class_type = Class;
+		};
+
+		template <typename Return, typename Class, typename... Args>
+		struct lambda_traits<Return (Class::*)(Args...)>
+		{
+			using return_type = Return;
+			using args_tuple = std::tuple<Args...>;
+			using class_type = Class;
+		};
+
+		using lambda_trait = lambda_traits<decltype(&Func::operator())>;
+
+	public:
+		using tag_type = lambda_tag;
+		using return_type = typename lambda_trait::return_type;
+		using args_tuple = typename lambda_trait::args_tuple;
+		using class_type = typename lambda_trait::class_type;
+	};
+}
+
+#endif //BLT_META_FUNCTION_H
diff --git a/include/blt/meta/passthrough.h b/include/blt/meta/passthrough.h
new file mode 100644
index 0000000..3ea369d
--- /dev/null
+++ b/include/blt/meta/passthrough.h
@@ -0,0 +1,31 @@
+#pragma once
+/*
+ *  Copyright (C) 2024  Brett Terpstra
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef BLT_META_PASSTHROUGH_H
+#define BLT_META_PASSTHROUGH_H
+
+namespace blt::meta
+{
+	template <typename T>
+	struct passthrough
+	{
+		using type = T;
+	};
+}
+
+#endif //BLT_META_PASSTHROUGH_H
diff --git a/include/blt/meta/tuple_filters.h b/include/blt/meta/tuple_filters.h
new file mode 100644
index 0000000..033d35c
--- /dev/null
+++ b/include/blt/meta/tuple_filters.h
@@ -0,0 +1,80 @@
+#pragma once
+/*
+ *  Copyright (C) 2024  Brett Terpstra
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef BLT_META_FILTER_VOID_H
+#define BLT_META_FILTER_VOID_H
+
+#include <tuple>
+#include <type_traits>
+
+namespace blt::meta
+{
+	template <typename... Ts>
+	struct filter_void;
+
+	template <>
+	struct filter_void<>
+	{
+		using type = std::tuple<>;
+	};
+
+	template <typename T, typename... Ts>
+	struct filter_void<T, Ts...>
+	{
+		using type = std::conditional_t<std::is_void_v<T>, typename filter_void<Ts...>::type, decltype(std::tuple_cat(
+											std::declval<std::tuple<T>>(), std::declval<typename filter_void<Ts...>::type>()))>;
+	};
+
+	template <typename... Ts>
+	struct filter_void<std::tuple<Ts...>>
+	{
+		using type = typename filter_void<Ts...>::type;
+	};
+
+	template <typename... Ts>
+	using filter_void_t = typename filter_void<Ts...>::type;
+
+	template <template<typename...> typename Func, typename ArgsTuple, typename... Ts>
+	struct filter_func;
+
+	template <template<typename...> typename Func, typename ArgsTuple>
+	struct filter_func<Func, ArgsTuple>
+	{
+		using type = std::tuple<>;
+	};
+
+	template <template<typename...> typename Func, typename... Args, typename T, typename... Ts>
+	struct filter_func<Func, std::tuple<Args...>, T, Ts...>
+	{
+		using type = std::conditional_t<Func<T, Args...>::value, typename filter_func<Func, std::tuple<Args...>, Ts...>::type, decltype(
+											std::tuple_cat(std::declval<std::tuple<T>>(),
+															std::declval<typename filter_func<Func, std::tuple<Args...>, Ts...>::type>()))>;
+	};
+
+	template <template<typename...> typename Func, typename ArgsTuple, typename... Ts>
+	struct filter_func<Func, ArgsTuple, std::tuple<Ts...>>
+	{
+		using type = typename filter_func<Func, ArgsTuple, Ts...>::type;
+	};
+
+	template <template<typename...> typename Func, typename ArgsTuple, typename... Ts>
+	using filter_func_t = typename filter_func<Func, ArgsTuple, Ts...>::type;
+
+}
+
+#endif //BLT_META_FILTER_VOID_H
diff --git a/include/blt/std/variant.h b/include/blt/std/variant.h
index dc117f1..da4c108 100644
--- a/include/blt/std/variant.h
+++ b/include/blt/std/variant.h
@@ -24,6 +24,8 @@
 #include <tuple>
 #include <type_traits>
 #include <variant>
+#include <blt/meta/passthrough.h>
+#include <blt/meta/tuple_filters.h>
 #include <blt/std/types.h>
 
 namespace blt
@@ -33,37 +35,13 @@ namespace blt
 
 	namespace detail
 	{
-		template <typename... Ts>
-		struct filter_void;
-
-		template <>
-		struct filter_void<>
-		{
-			using type = std::tuple<>;
-		};
-
-		template <typename T, typename... Ts>
-		struct filter_void<T, Ts...>
-		{
-			using type = std::conditional_t<std::is_void_v<T>, typename filter_void<Ts...>::type, decltype(std::tuple_cat(
-												std::declval<std::tuple<T>>(), std::declval<typename filter_void<Ts...>::type>()))>;
-		};
-
-		template <typename... Ts>
-		using filter_void_t = typename filter_void<Ts...>::type;
-
-		template<typename T>
-		struct passthrough
-		{
-			using type = T;
-		};
-
 		template <typename Type, typename Func, typename... Args>
 		struct member_func_meta
 		{
 			using can_invoke = std::is_invocable<Func, Type, Args...>;
 
-			using return_type = typename std::conditional_t<can_invoke::value, std::invoke_result<Func, Type, Args...>, passthrough<void>>::type;
+			using return_type = typename std::conditional_t<can_invoke::value, std::invoke_result<Func, Type, Args...>, meta::passthrough<void>>::type
+			;
 		};
 
 		template <typename Func, typename ArgsTuple, typename... Types>
@@ -73,7 +51,7 @@ namespace blt
 		struct member_call_return_type<Func, std::tuple<Args...>, Types...>
 		{
 			using result_types = std::tuple<member_func_meta<Types, Func, Args...>...>;
-			using non_void_result_types = typename filter_void<typename member_func_meta<Types, Func, Args...>::return_type...>::type;
+			using non_void_result_types = meta::filter_void_t<typename member_func_meta<Types, Func, Args...>::return_type...>;
 
 			static constexpr bool all_void = std::tuple_size_v<non_void_result_types> == 0;
 			static constexpr bool some_void = std::tuple_size_v<non_void_result_types> != sizeof...(Types);
@@ -83,12 +61,35 @@ namespace blt
 			using return_type = std::conditional_t<all_void, void, std::conditional_t<some_void, std::optional<first_return>, first_return>>;
 		};
 
+		template <typename Func, typename... Types>
+		struct visit_func_meta
+		{
+			using result_tuple = std::tuple<typename std::conditional_t<
+				std::is_invocable_v<Func, Types>, std::invoke_result<Func, Types>, meta::passthrough<void>>::type...>;
+
+			using non_void_results = meta::filter_void_t<result_tuple>;
+
+			using return_type = std::tuple_element_t<
+				0, std::conditional_t<std::tuple_size_v<non_void_results> == 0, std::tuple<void>, non_void_results>>;
+		};
+
 		template <typename FuncTuple, typename TypesTuple>
 		struct visit_return_type;
 
 		template <typename... Funcs, typename... Types>
 		struct visit_return_type<std::tuple<Funcs...>, std::tuple<Types...>>
-		{};
+		{
+			using return_tuple = std::tuple<typename visit_func_meta<Funcs, Types...>::return_type...>;
+
+			using non_void_returns = meta::filter_void_t<return_tuple>;
+
+			using first_return = std::tuple_element_t<
+				0, std::conditional_t<std::tuple_size_v<non_void_returns> == 0, std::tuple<void>, non_void_returns>>;
+
+			static constexpr bool all_void = std::tuple_size_v<non_void_returns> == 0;
+			static constexpr bool some_void = std::tuple_size_v<non_void_returns> != std::tuple_size_v<return_tuple>;
+			static constexpr bool all_same = meta::filter_func_t<std::is_same, std::tuple<first_return>, non_void_returns>::value;
+		};
 	}
 
 	/*
@@ -214,7 +215,7 @@ namespace blt
 		}
 
 		template <typename MemberFunc, typename... Args>
-		constexpr auto call_member(const MemberFunc func, Args&&... args)
+		constexpr auto call_member(const MemberFunc func, Args&&... args) -> decltype(auto)
 		{
 			using meta = detail::member_call_return_type<MemberFunc, std::tuple<Args...>, Types...>;
 			return visit([&](auto&& value) -> typename meta::return_type {
@@ -356,12 +357,6 @@ namespace blt
 		}
 
 	private:
-		template <typename Derived, typename Base, typename ReturnType, typename... Args>
-		static auto cast_member_ptr(ReturnType (Base::*base_func)(Args...))
-		{
-			return reinterpret_cast<ReturnType (Derived::*)(Args...)>(base_func);
-		}
-
 		value_type m_variant;
 	};
 
diff --git a/tests/variant_tests.cpp b/tests/variant_tests.cpp
index b0c2e81..6d18ff1 100644
--- a/tests/variant_tests.cpp
+++ b/tests/variant_tests.cpp
@@ -34,12 +34,12 @@ struct mutate_type : base_type
 
 struct type1 final : base_type
 {
-	[[nodiscard]] int simple() const override // NOLINT
+	[[nodiscard]] int simple() const final // NOLINT
 	{
 		return 1;
 	}
 
-	[[nodiscard]] std::string to_string() const override // NOLINT
+	[[nodiscard]] std::string to_string() const final // NOLINT
 	{
 		return "Type1";
 	}
@@ -48,12 +48,12 @@ struct type1 final : base_type
 
 struct type2 final : base_type
 {
-	[[nodiscard]] int simple() const override // NOLINT
+	[[nodiscard]] int simple() const final // NOLINT
 	{
 		return 2;
 	}
 
-	[[nodiscard]] std::string to_string() const override // NOLINT
+	[[nodiscard]] std::string to_string() const final // NOLINT
 	{
 		return "Type2";
 	}
@@ -62,12 +62,12 @@ struct type2 final : base_type
 
 struct type3 final : base_type
 {
-	[[nodiscard]] int simple() const override // NOLINT
+	[[nodiscard]] int simple() const final // NOLINT
 	{
 		return 3;
 	}
 
-	[[nodiscard]] std::string to_string() const override // NOLINT
+	[[nodiscard]] std::string to_string() const final // NOLINT
 	{
 		return "Type3";
 	}
@@ -79,17 +79,17 @@ struct storing_type1 final : mutate_type
 	{
 	}
 
-	[[nodiscard]] int simple() const override // NOLINT
+	[[nodiscard]] int simple() const final // NOLINT
 	{
 		return internal;
 	}
 
-	void mutate(const int i) override
+	void mutate(const int i) final
 	{
 		internal = i;
 	}
 
-	[[nodiscard]] std::string to_string() const override // NOLINT
+	[[nodiscard]] std::string to_string() const final // NOLINT
 	{
 		return "Storing Type: {" + std::to_string(internal) + "}";
 	}
@@ -103,17 +103,17 @@ struct storing_type2 final : mutate_type
 	{
 	}
 
-	[[nodiscard]] int simple() const override // NOLINT
+	[[nodiscard]] int simple() const final // NOLINT
 	{
 		return static_cast<int>(internal);
 	}
 
-	void mutate(const int i) override
+	void mutate(const int i) final
 	{
 		internal = static_cast<float>(i) * 2.2534f;
 	}
 
-	[[nodiscard]] std::string to_string() const override // NOLINT
+	[[nodiscard]] std::string to_string() const final // NOLINT
 	{
 		return "Storing Type: {" + std::to_string(internal) + "}";
 	}