From c13864bfc0bbbf34fe6cf8e9a304937043757292 Mon Sep 17 00:00:00 2001
From: Spartan322 <Megacake1234@gmail.com>
Date: Tue, 30 Dec 2025 15:10:48 -0500
Subject: [PATCH] Add strict_regular_invocable_r to concepts Prefer
 strict_regular_invocable_r for IndexedFlatMap callables arguments

---
 src/openvic-simulation/core/template/Concepts.hpp | 6 ++++++
 src/openvic-simulation/types/IndexedFlatMap.hpp   | 8 ++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/openvic-simulation/core/template/Concepts.hpp b/src/openvic-simulation/core/template/Concepts.hpp
index 3063bfb9..1c7193cd 100644
--- a/src/openvic-simulation/core/template/Concepts.hpp
+++ b/src/openvic-simulation/core/template/Concepts.hpp
@@ -226,4 +226,10 @@ namespace OpenVic {
 	concept mul_add_assignable = requires(Lhs& lhs, const A a, const B b) {
 		{ lhs += a * b } -> std::same_as<Lhs&>;
 	};
+
+	// Return type is strictly evaluated with same_as
+	template<typename F, typename Return, typename... Args>
+	concept strict_regular_invocable_r = std::regular_invocable<F, Args...> && requires(F f, Args&&... args) {
+		{ f(static_cast<Args>(args)...) } -> std::same_as<Return>;
+	};
 }
diff --git a/src/openvic-simulation/types/IndexedFlatMap.hpp b/src/openvic-simulation/types/IndexedFlatMap.hpp
index 051defad..a1af1048 100644
--- a/src/openvic-simulation/types/IndexedFlatMap.hpp
+++ b/src/openvic-simulation/types/IndexedFlatMap.hpp
@@ -604,7 +604,7 @@ namespace OpenVic {
 		*
 		* @note This method requires `ValueType` to be copy-assignable.
 		*/
-		void reinitialize_with_generator(fu2::function<ValueType(ForwardedKeyType const&)> value_generator)
+		void reinitialize_with_generator(strict_regular_invocable_r<ValueType, ForwardedKeyType const&> auto&& value_generator)
 		requires std::copyable<ValueType> {
 			for (iterator it = begin(); it < end(); it++) {
 				auto& [key, value] = *it;
@@ -622,7 +622,7 @@ namespace OpenVic {
 		* @note This method destroys existing elements and constructs new ones in place,
 		* which is often more efficient for move-only types.
 		*/
-		void reinitialize_with_generator(fu2::function<ValueType(ForwardedKeyType const&)> value_generator)
+		void reinitialize_with_generator(strict_regular_invocable_r<ValueType, ForwardedKeyType const&> auto&& value_generator)
 		requires std::movable<ValueType> && (!std::copyable<ValueType>) {
 			values.clear();
 			for (ForwardedKeyType const& key : keys) {
@@ -735,7 +735,7 @@ namespace OpenVic {
 		template <typename OtherValueType>
 		IndexedFlatMap<ForwardedKeyType, ValueType> divide_handle_zero(
 			IndexedFlatMap<ForwardedKeyType,OtherValueType> const& other,
-			fu2::function<ValueType(ValueType const&, OtherValueType const&)> handle_div_by_zero
+			strict_regular_invocable_r<ValueType, ValueType const&, OtherValueType const&> auto&& handle_div_by_zero
 		) const requires divisible<ValueType,OtherValueType,ValueType> {
 			static_assert(has_index<ForwardedKeyType>);
 			if (!check_subset_span_match(other)) {
@@ -745,7 +745,7 @@ namespace OpenVic {
 			return IndexedFlatMap(keys, [&](ForwardedKeyType const& key) {
 				if (other.contains(key)) {
 					if (other.at(key) == static_cast<ValueType>(0)) {
-						return handle_div_by_zero(
+						return std::forward(handle_div_by_zero)(
 							this->at(key),
 							other.at(key)
 						);