From f62fe088383cea66312a300c5c6e7c1d7669809f Mon Sep 17 00:00:00 2001
From: saganatt <8majak8@gmail.com>
Date: Wed, 8 Dec 2021 22:51:14 +0100
Subject: [PATCH 1/2] Extend pack with unique types and interleaved

---
 Framework/Foundation/include/Framework/Pack.h | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/Framework/Foundation/include/Framework/Pack.h b/Framework/Foundation/include/Framework/Pack.h
index 62c1f10338777..97c7db418a457 100644
--- a/Framework/Foundation/include/Framework/Pack.h
+++ b/Framework/Foundation/include/Framework/Pack.h
@@ -90,6 +90,15 @@ constexpr auto concatenate_pack(P1 p1, P2 p2, Ps... ps)
 template <typename... Ps>
 using concatenated_pack_t = decltype(concatenate_pack(Ps{}...));
 
+template <typename... Args1, typename... Args2>
+constexpr auto interleave_pack(pack<Args1...>, pack<Args2...>)
+{
+  return concatenated_pack_t<pack<Args1, Args2>...>{};
+}
+
+template <typename... Ps>
+using interleaved_pack_t = decltype(interleave_pack(Ps{}...));
+
 /// Selects from the pack types that satisfy the Condition
 template <template <typename> typename Condition, typename Result>
 constexpr auto select_pack(Result result, pack<>)
@@ -248,6 +257,25 @@ constexpr auto concatenate_pack_unique(P1 p1, P2 p2, Ps... ps)
 template <typename... Ps>
 using concatenated_pack_unique_t = decltype(concatenate_pack_unique(Ps{}...));
 
+template <typename T, typename T2>
+struct add_type_impl;
+template <typename T, typename... Ts>
+struct add_type_impl<T, pack<Ts...>> {
+  using type = std::conditional_t<sizeof...(Ts) == 0, pack<T>, std::conditional_t<has_type_v<T, pack<Ts...>>, pack<Ts...>, pack<T, Ts...>>>;
+};
+template <typename T, typename T2>
+using add_type = typename add_type_impl<T, T2>::type;
+
+template <typename P, typename PT = pack<>>
+struct unique_types_impl {
+  using type = PT;
+};
+template <typename PT, typename T, typename... Ts>
+struct unique_types_impl<pack<T, Ts...>, PT> : unique_types_impl<pack<Ts...>, add_type<T, PT>> {
+};
+template <typename P>
+using unique_types = typename unique_types_impl<P>::type;
+
 } // namespace o2::framework
 
 #endif // O2_FRAMEWORK_PACK_H_

From c8c7dbaa845487c1875f1fe4094f56aa67227141 Mon Sep 17 00:00:00 2001
From: saganatt <8majak8@gmail.com>
Date: Thu, 9 Dec 2021 12:43:33 +0100
Subject: [PATCH 2/2] Rewrote interleave and unique_pack

---
 Framework/Foundation/include/Framework/Pack.h | 32 ++++++++-----------
 .../test/test_FunctionalHelpers.cxx           |  3 ++
 2 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/Framework/Foundation/include/Framework/Pack.h b/Framework/Foundation/include/Framework/Pack.h
index 97c7db418a457..7b3899060c491 100644
--- a/Framework/Foundation/include/Framework/Pack.h
+++ b/Framework/Foundation/include/Framework/Pack.h
@@ -85,7 +85,7 @@ template <typename P1, typename P2, typename... Ps>
 constexpr auto concatenate_pack(P1 p1, P2 p2, Ps... ps)
 {
   return concatenate_pack(p1, concatenate_pack(p2, ps...));
-};
+}
 
 template <typename... Ps>
 using concatenated_pack_t = decltype(concatenate_pack(Ps{}...));
@@ -96,8 +96,8 @@ constexpr auto interleave_pack(pack<Args1...>, pack<Args2...>)
   return concatenated_pack_t<pack<Args1, Args2>...>{};
 }
 
-template <typename... Ps>
-using interleaved_pack_t = decltype(interleave_pack(Ps{}...));
+template <typename P1, typename P2>
+using interleaved_pack_t = decltype(interleave_pack(P1{}, P2{}));
 
 /// Selects from the pack types that satisfy the Condition
 template <template <typename> typename Condition, typename Result>
@@ -257,24 +257,20 @@ constexpr auto concatenate_pack_unique(P1 p1, P2 p2, Ps... ps)
 template <typename... Ps>
 using concatenated_pack_unique_t = decltype(concatenate_pack_unique(Ps{}...));
 
-template <typename T, typename T2>
-struct add_type_impl;
-template <typename T, typename... Ts>
-struct add_type_impl<T, pack<Ts...>> {
-  using type = std::conditional_t<sizeof...(Ts) == 0, pack<T>, std::conditional_t<has_type_v<T, pack<Ts...>>, pack<Ts...>, pack<T, Ts...>>>;
-};
-template <typename T, typename T2>
-using add_type = typename add_type_impl<T, T2>::type;
+template <typename PT>
+constexpr auto unique_pack(pack<>, PT p2)
+{
+  return p2;
+}
 
-template <typename P, typename PT = pack<>>
-struct unique_types_impl {
-  using type = PT;
-};
 template <typename PT, typename T, typename... Ts>
-struct unique_types_impl<pack<T, Ts...>, PT> : unique_types_impl<pack<Ts...>, add_type<T, PT>> {
-};
+constexpr auto unique_pack(pack<T, Ts...>, PT p2)
+{
+  return unique_pack(pack<Ts...>{}, concatenate_pack_unique(pack<T>{}, p2));
+}
+
 template <typename P>
-using unique_types = typename unique_types_impl<P>::type;
+using unique_pack_t = decltype(unique_pack(P{}, pack<>{}));
 
 } // namespace o2::framework
 
diff --git a/Framework/Foundation/test/test_FunctionalHelpers.cxx b/Framework/Foundation/test/test_FunctionalHelpers.cxx
index e77f9a0b88504..7871ed0f337e8 100644
--- a/Framework/Foundation/test/test_FunctionalHelpers.cxx
+++ b/Framework/Foundation/test/test_FunctionalHelpers.cxx
@@ -51,6 +51,9 @@ BOOST_AUTO_TEST_CASE(TestOverride)
   print_pack<p3>();
   static_assert(std::is_same_v<p3, pack<float, bool, int, double, char>>, "pack should not have duplicated types");
 
+  static_assert(std::is_same_v<unique_pack_t<pack<int, float, int, float, char, char>>, pack<char, float, int>>, "pack should not have duplicated types");
+  static_assert(std::is_same_v<interleaved_pack_t<pack<int, float, int>, pack<char, bool, char>>, pack<int, char, float, bool, int, char>>, "interleaved packs of the same size");
+
   struct ForwardDeclared;
   static_assert(is_type_complete_v<ForwardDeclared> == false, "This should not be complete because the struct is simply forward declared.");