From 916337a5727b5a53302467f443b9207673d3d988 Mon Sep 17 00:00:00 2001
From: PraisePancakes <100659653+PraisePancakes@users.noreply.github.com>
Date: Fri, 13 Jun 2025 11:06:12 -0400
Subject: [PATCH 1/7] changed fplus::internal::get_index to reduce templated
 recursion and introduced contains metafunction to test whether type list
 contains a type

---
 include/fplus/variant.hpp                  | 27 +++++++++----------
 include_all_in_one/include/fplus/fplus.hpp | 31 ++++++++++------------
 2 files changed, 26 insertions(+), 32 deletions(-)

diff --git a/include/fplus/variant.hpp b/include/fplus/variant.hpp
index 732ffa38..9e1dc45d 100644
--- a/include/fplus/variant.hpp
+++ b/include/fplus/variant.hpp
@@ -93,23 +93,20 @@ namespace internal {
         typedef std::shared_ptr<T> type;
     };
 
-    // http://stackoverflow.com/a/27588263/1866775
-
-    template <typename T, typename... Ts>
-    struct get_index;
-
-    template <typename T, typename... Ts>
-    struct get_index<T, T, Ts...> : std::integral_constant<std::size_t, 0> {
+    template <typename What, typename... Ts>
+    struct contains {
+        /// True if T is in Ts...
+        constexpr static bool value = (std::is_same_v<What, Ts> || ...);
     };
 
-    template <typename T, typename Tail, typename... Ts>
-    struct get_index<T, Tail, Ts...> : std::integral_constant<std::size_t, 1 + get_index<T, Ts...>::value> {
-    };
-
-    template <typename T>
-    struct get_index<T> {
-        // condition is always false, but should be dependant of T
-        static_assert(sizeof(T) == 0, "element not found");
+    template <typename What, typename... Ts>
+    struct get_index {
+        /// Index of type T in List.
+        constexpr static auto index = []() {
+            return (contains<What, Ts...>::value ? []() {signed i = 0;
+            (... && (!std::is_same_v<What, Ts...> && ++i));
+            return i; }() : -1);
+        }();
     };
 
     template <typename T, typename... Ts>
diff --git a/include_all_in_one/include/fplus/fplus.hpp b/include_all_in_one/include/fplus/fplus.hpp
index 80894cdd..a71e5ab7 100644
--- a/include_all_in_one/include/fplus/fplus.hpp
+++ b/include_all_in_one/include/fplus/fplus.hpp
@@ -3295,7 +3295,7 @@ namespace internal {
         std::size_t pos_;
     };
 
-#if defined(_MSC_VER) && _MSC_VER >= 1900
+#if defined(_MSC_VER) && _MSC_VER >= 1900 && _MSC_VER < 1915
     template <typename T, std::size_t N>
     struct std::_Is_checked_helper<array_back_insert_iterator<T, N>>
         : public true_type { // mark array_back_insert_iterator as checked
@@ -14329,23 +14329,20 @@ namespace internal {
         typedef std::shared_ptr<T> type;
     };
 
-    // http://stackoverflow.com/a/27588263/1866775
-
-    template <typename T, typename... Ts>
-    struct get_index;
-
     template <typename T, typename... Ts>
-    struct get_index<T, T, Ts...> : std::integral_constant<std::size_t, 0> {
-    };
-
-    template <typename T, typename Tail, typename... Ts>
-    struct get_index<T, Tail, Ts...> : std::integral_constant<std::size_t, 1 + get_index<T, Ts...>::value> {
-    };
-
-    template <typename T>
-    struct get_index<T> {
-        // condition is always false, but should be dependant of T
-        static_assert(sizeof(T) == 0, "element not found");
+    struct contains {
+        /// True if T is in Ts...
+        constexpr static bool value = (std::is_same_v<T, Ts> || ...);
+    };
+
+    template <typename What, typename... Ts>
+    struct get_index {
+        /// Index of type T in List.
+        constexpr static auto index = []() {
+            return (contains<What, Ts...>::value ? []() {signed i = 0;
+            (... && (!std::is_same_v<What, Ts...> && ++i));
+            return i; }() : -1);
+        }();
     };
 
     template <typename T, typename... Ts>

From 6c478a234273565ad1f7889543bf0c67bbbc1be5 Mon Sep 17 00:00:00 2001
From: PraisePancakes <100659653+PraisePancakes@users.noreply.github.com>
Date: Sat, 14 Jun 2025 10:20:13 -0400
Subject: [PATCH 2/7] fixed get_index error

---
 CMakeLists.txt                             | 2 +-
 include/fplus/variant.hpp                  | 2 +-
 include_all_in_one/include/fplus/fplus.hpp | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d21a29a1..e2633a86 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,7 +21,7 @@ target_include_directories(
         "$<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>"
 )
 
-target_compile_features(fplus INTERFACE cxx_std_14)
+target_compile_features(fplus INTERFACE cxx_std_23)
 
 find_package(Threads REQUIRED)
 target_link_libraries(fplus INTERFACE Threads::Threads)
diff --git a/include/fplus/variant.hpp b/include/fplus/variant.hpp
index 9e1dc45d..edfbd356 100644
--- a/include/fplus/variant.hpp
+++ b/include/fplus/variant.hpp
@@ -104,7 +104,7 @@ namespace internal {
         /// Index of type T in List.
         constexpr static auto index = []() {
             return (contains<What, Ts...>::value ? []() {signed i = 0;
-            (... && (!std::is_same_v<What, Ts...> && ++i));
+            (... && (!std::is_same_v<What, Ts> && ++i));
             return i; }() : -1);
         }();
     };
diff --git a/include_all_in_one/include/fplus/fplus.hpp b/include_all_in_one/include/fplus/fplus.hpp
index a71e5ab7..4a411768 100644
--- a/include_all_in_one/include/fplus/fplus.hpp
+++ b/include_all_in_one/include/fplus/fplus.hpp
@@ -14329,10 +14329,10 @@ namespace internal {
         typedef std::shared_ptr<T> type;
     };
 
-    template <typename T, typename... Ts>
+    template <typename What, typename... Ts>
     struct contains {
         /// True if T is in Ts...
-        constexpr static bool value = (std::is_same_v<T, Ts> || ...);
+        constexpr static bool value = (std::is_same_v<What, Ts> || ...);
     };
 
     template <typename What, typename... Ts>

From 9edce489fb9563cd942f28703480d0ee8dd7374f Mon Sep 17 00:00:00 2001
From: PraisePancakes <100659653+PraisePancakes@users.noreply.github.com>
Date: Sun, 15 Jun 2025 23:17:30 -0400
Subject: [PATCH 3/7] testing local environment

---
 include/fplus/variant.hpp                  | 7 ++++---
 include_all_in_one/include/fplus/fplus.hpp | 9 +++++----
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/include/fplus/variant.hpp b/include/fplus/variant.hpp
index edfbd356..6e7f866f 100644
--- a/include/fplus/variant.hpp
+++ b/include/fplus/variant.hpp
@@ -102,10 +102,11 @@ namespace internal {
     template <typename What, typename... Ts>
     struct get_index {
         /// Index of type T in List.
-        constexpr static auto index = []() {
-            return (contains<What, Ts...>::value ? []() {signed i = 0;
+        static_assert(contains<What, Ts...>::value, "element is not in list");
+        constexpr static auto value = []() {
+            return ([]() {std::size_t i = 0;
             (... && (!std::is_same_v<What, Ts> && ++i));
-            return i; }() : -1);
+            return i; }());
         }();
     };
 
diff --git a/include_all_in_one/include/fplus/fplus.hpp b/include_all_in_one/include/fplus/fplus.hpp
index 4a411768..99a0b111 100644
--- a/include_all_in_one/include/fplus/fplus.hpp
+++ b/include_all_in_one/include/fplus/fplus.hpp
@@ -14338,10 +14338,11 @@ namespace internal {
     template <typename What, typename... Ts>
     struct get_index {
         /// Index of type T in List.
-        constexpr static auto index = []() {
-            return (contains<What, Ts...>::value ? []() {signed i = 0;
-            (... && (!std::is_same_v<What, Ts...> && ++i));
-            return i; }() : -1);
+        static_assert(contains<What, Ts...>::value, "element is not in list");
+        constexpr static auto value = []() {
+            return ([]() {std::size_t i = 0;
+            (... && (!std::is_same_v<What, Ts> && ++i));
+            return i; }());
         }();
     };
 

From 0bdf71f5688bb26513a9e44b562ca4d2f32f56a1 Mon Sep 17 00:00:00 2001
From: PraisePancakes <100659653+PraisePancakes@users.noreply.github.com>
Date: Mon, 16 Jun 2025 09:19:21 -0400
Subject: [PATCH 4/7] changed standard version to test CI

---
 CMakeLists.txt      | 2 +-
 test/CMakeLists.txt | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e2633a86..f7282a3f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,7 +21,7 @@ target_include_directories(
         "$<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>"
 )
 
-target_compile_features(fplus INTERFACE cxx_std_23)
+target_compile_features(fplus INTERFACE cxx_std_17)
 
 find_package(Threads REQUIRED)
 target_link_libraries(fplus INTERFACE Threads::Threads)
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 0a10914a..316b46c8 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -75,6 +75,6 @@ foreach (name IN LISTS tests)
             FunctionalPlus::fplus
             doctest::doctest
     )
-    target_compile_features("${name}" PRIVATE cxx_std_14)
+    target_compile_features("${name}" PRIVATE cxx_std_17)
     doctest_discover_tests("${name}")
 endforeach ()

From 1ff0b33cb42d2ba5aaa626fa890d37904aa230d1 Mon Sep 17 00:00:00 2001
From: PraisePancakes <100659653+PraisePancakes@users.noreply.github.com>
Date: Mon, 16 Jun 2025 09:27:37 -0400
Subject: [PATCH 5/7] reverted test build cmake to 14

---
 test/CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 316b46c8..0a10914a 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -75,6 +75,6 @@ foreach (name IN LISTS tests)
             FunctionalPlus::fplus
             doctest::doctest
     )
-    target_compile_features("${name}" PRIVATE cxx_std_17)
+    target_compile_features("${name}" PRIVATE cxx_std_14)
     doctest_discover_tests("${name}")
 endforeach ()

From 982899e2ff6aabbf8c9b4f9b9b24a37b02bf6ae4 Mon Sep 17 00:00:00 2001
From: PraisePancakes <100659653+PraisePancakes@users.noreply.github.com>
Date: Mon, 16 Jun 2025 12:18:11 -0400
Subject: [PATCH 6/7] changed c++23 to 17

---
 include/fplus/function_traits.hpp          | 34 +++++++++++-----------
 include_all_in_one/include/fplus/fplus.hpp | 34 +++++++++++-----------
 test/CMakeLists.txt                        |  4 +--
 3 files changed, 35 insertions(+), 37 deletions(-)

diff --git a/include/fplus/function_traits.hpp b/include/fplus/function_traits.hpp
index 9598f748..3858ef2a 100644
--- a/include/fplus/function_traits.hpp
+++ b/include/fplus/function_traits.hpp
@@ -85,22 +85,6 @@ namespace utils {
         : public function_traits<decltype(&T::operator())> {
     };
 
-    namespace xx_impl {
-        template <typename C, typename R, typename... A>
-        struct memfn_type {
-            typedef typename std::conditional<
-                std::is_const<C>::value,
-                typename std::conditional<
-                    std::is_volatile<C>::value,
-                    R (C::*)(A...) const volatile,
-                    R (C::*)(A...) const>::type,
-                typename std::conditional<
-                    std::is_volatile<C>::value,
-                    R (C::*)(A...) volatile,
-                    R (C::*)(A...)>::type>::type type;
-        };
-    }
-
     template <typename ReturnType, typename... Args>
     struct function_traits<ReturnType(Args...)> {
         /**
@@ -145,6 +129,22 @@ namespace utils {
         };
     };
 
+    namespace xx_impl {
+        template <typename C, typename R, typename... A>
+        struct memfn_type {
+            typedef typename std::conditional<
+                std::is_const<C>::value,
+                typename std::conditional<
+                    std::is_volatile<C>::value,
+                    R (C::*)(A...) const volatile,
+                    R (C::*)(A...) const>::type,
+                typename std::conditional<
+                    std::is_volatile<C>::value,
+                    R (C::*)(A...) volatile,
+                    R (C::*)(A...)>::type>::type type;
+        };
+    }
+
 #if __cplusplus > 201510L
 
     template <typename ReturnType, typename... Args>
@@ -441,7 +441,7 @@ namespace internal {
     };
 
     template <typename ReturnType, typename ClassType, typename... Args>
-    struct has_function_traits<ReturnType (ClassType::*)(Args...)&> : std::true_type {
+    struct has_function_traits<ReturnType (ClassType::*)(Args...) &> : std::true_type {
     };
 
     template <typename ReturnType, typename ClassType, typename... Args>
diff --git a/include_all_in_one/include/fplus/fplus.hpp b/include_all_in_one/include/fplus/fplus.hpp
index 99a0b111..bf290851 100644
--- a/include_all_in_one/include/fplus/fplus.hpp
+++ b/include_all_in_one/include/fplus/fplus.hpp
@@ -344,22 +344,6 @@ namespace utils {
         : public function_traits<decltype(&T::operator())> {
     };
 
-    namespace xx_impl {
-        template <typename C, typename R, typename... A>
-        struct memfn_type {
-            typedef typename std::conditional<
-                std::is_const<C>::value,
-                typename std::conditional<
-                    std::is_volatile<C>::value,
-                    R (C::*)(A...) const volatile,
-                    R (C::*)(A...) const>::type,
-                typename std::conditional<
-                    std::is_volatile<C>::value,
-                    R (C::*)(A...) volatile,
-                    R (C::*)(A...)>::type>::type type;
-        };
-    }
-
     template <typename ReturnType, typename... Args>
     struct function_traits<ReturnType(Args...)> {
         /**
@@ -404,6 +388,22 @@ namespace utils {
         };
     };
 
+    namespace xx_impl {
+        template <typename C, typename R, typename... A>
+        struct memfn_type {
+            typedef typename std::conditional<
+                std::is_const<C>::value,
+                typename std::conditional<
+                    std::is_volatile<C>::value,
+                    R (C::*)(A...) const volatile,
+                    R (C::*)(A...) const>::type,
+                typename std::conditional<
+                    std::is_volatile<C>::value,
+                    R (C::*)(A...) volatile,
+                    R (C::*)(A...)>::type>::type type;
+        };
+    }
+
 #if __cplusplus > 201510L
 
     template <typename ReturnType, typename... Args>
@@ -700,7 +700,7 @@ namespace internal {
     };
 
     template <typename ReturnType, typename ClassType, typename... Args>
-    struct has_function_traits<ReturnType (ClassType::*)(Args...)&> : std::true_type {
+    struct has_function_traits<ReturnType (ClassType::*)(Args...) &> : std::true_type {
     };
 
     template <typename ReturnType, typename ClassType, typename... Args>
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 0a10914a..025344cf 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -15,9 +15,7 @@ include(../cmake/warnings.cmake)
 find_package(doctest 2.4.11 CONFIG REQUIRED)
 # for doctest_discover_tests
 include(doctest)
-
 enable_testing()
-
 set(
         tests
         show_versions
@@ -75,6 +73,6 @@ foreach (name IN LISTS tests)
             FunctionalPlus::fplus
             doctest::doctest
     )
-    target_compile_features("${name}" PRIVATE cxx_std_14)
+    target_compile_features("${name}" PRIVATE cxx_std_17)
     doctest_discover_tests("${name}")
 endforeach ()

From 7ce200c165d8447b7cc4137b49b35a7bd5d7dbdf Mon Sep 17 00:00:00 2001
From: PraisePancakes <100659653+PraisePancakes@users.noreply.github.com>
Date: Mon, 16 Jun 2025 12:23:07 -0400
Subject: [PATCH 7/7] reverted xx_impl

---
 include/fplus/function_traits.hpp | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/include/fplus/function_traits.hpp b/include/fplus/function_traits.hpp
index 3858ef2a..9c0bac76 100644
--- a/include/fplus/function_traits.hpp
+++ b/include/fplus/function_traits.hpp
@@ -85,6 +85,21 @@ namespace utils {
         : public function_traits<decltype(&T::operator())> {
     };
 
+    namespace xx_impl {
+        template <typename C, typename R, typename... A>
+        struct memfn_type {
+            typedef typename std::conditional<
+                std::is_const<C>::value,
+                typename std::conditional<
+                    std::is_volatile<C>::value,
+                    R (C::*)(A...) const volatile,
+                    R (C::*)(A...) const>::type,
+                typename std::conditional<
+                    std::is_volatile<C>::value,
+                    R (C::*)(A...) volatile,
+                    R (C::*)(A...)>::type>::type type;
+        };
+    }
     template <typename ReturnType, typename... Args>
     struct function_traits<ReturnType(Args...)> {
         /**
@@ -129,22 +144,6 @@ namespace utils {
         };
     };
 
-    namespace xx_impl {
-        template <typename C, typename R, typename... A>
-        struct memfn_type {
-            typedef typename std::conditional<
-                std::is_const<C>::value,
-                typename std::conditional<
-                    std::is_volatile<C>::value,
-                    R (C::*)(A...) const volatile,
-                    R (C::*)(A...) const>::type,
-                typename std::conditional<
-                    std::is_volatile<C>::value,
-                    R (C::*)(A...) volatile,
-                    R (C::*)(A...)>::type>::type type;
-        };
-    }
-
 #if __cplusplus > 201510L
 
     template <typename ReturnType, typename... Args>