From 587acb304a40059211a449acbb754567fb09d038 Mon Sep 17 00:00:00 2001
From: Razakhel <romain.milbert@gmail.com>
Date: Sun, 3 Nov 2024 14:56:19 +0100
Subject: [PATCH] [Math/Vector] Added structured bindings support for
 Raz::Vector

- Added std::tuple_size<Vector>, std::tuple_element<Vector> & get<I>(Vector)
---
 include/RaZ/Math/Vector.hpp   | 40 ++++++++++++++
 tests/src/RaZ/Math/Vector.cpp | 98 +++++++++++++++++++++++++++++++++++
 2 files changed, 138 insertions(+)

diff --git a/include/RaZ/Math/Vector.hpp b/include/RaZ/Math/Vector.hpp
index e03bed1a..a97a98cb 100644
--- a/include/RaZ/Math/Vector.hpp
+++ b/include/RaZ/Math/Vector.hpp
@@ -293,8 +293,48 @@ constexpr Vec3f Z(0.f, 0.f, 1.f);
 
 } // namespace Axis
 
+/// Vector element fetching function for a constant lvalue reference.
+/// \tparam I Index of the element.
+/// \tparam T Type of the vector's data.
+/// \tparam Size Vector's size.
+/// \param vec Vector to get the element from.
+/// \return Constant lvalue reference on the vector's element.
+template <std::size_t I, typename T, std::size_t Size>
+constexpr const T& get(const Vector<T, Size>& vec) noexcept { static_assert(I < Size); return vec[I]; }
+
+/// Vector element fetching function for a non-constant lvalue reference.
+/// \tparam I Index of the element.
+/// \tparam T Type of the vector's data.
+/// \tparam Size Vector's size.
+/// \param vec Vector to get the element from.
+/// \return Non-constant lvalue reference on the vector's element.
+template <std::size_t I, typename T, std::size_t Size>
+constexpr T& get(Vector<T, Size>& vec) noexcept { static_assert(I < Size); return vec[I]; }
+
+/// Vector element fetching function for a non-constant rvalue reference.
+/// \tparam I Index of the element.
+/// \tparam T Type of the vector's data.
+/// \tparam Size Vector's size.
+/// \param vec Vector to get the element from.
+/// \return Non-constant rvalue reference on the vector's element.
+template <std::size_t I, typename T, std::size_t Size>
+constexpr T&& get(Vector<T, Size>&& vec) noexcept { static_assert(I < Size); return std::move(vec[I]); }
+
 } // namespace Raz
 
+/// Specialization of std::tuple_size for Vector.
+/// \tparam T Type of the vector's data.
+/// \tparam Size Vector's size.
+template <typename T, std::size_t Size>
+struct std::tuple_size<Raz::Vector<T, Size>> : std::integral_constant<std::size_t, Size> {};
+
+/// Specialization of std::tuple_element for Vector.
+/// \tparam I Index of the element.
+/// \tparam T Type of the vector's data.
+/// \tparam Size Vector's size.
+template <std::size_t I, typename T, std::size_t Size>
+struct std::tuple_element<I, Raz::Vector<T, Size>> { using type = T; };
+
 /// Specialization of std::hash for Vector.
 /// \tparam T Type of the vector's data.
 /// \tparam Size Vector's size.
diff --git a/tests/src/RaZ/Math/Vector.cpp b/tests/src/RaZ/Math/Vector.cpp
index 3cd307ea..c0de2ea0 100644
--- a/tests/src/RaZ/Math/Vector.cpp
+++ b/tests/src/RaZ/Math/Vector.cpp
@@ -7,6 +7,7 @@
 #include <catch2/catch_test_macros.hpp>
 
 #include <unordered_map>
+#include <utility>
 
 namespace {
 
@@ -322,6 +323,103 @@ TEST_CASE("Vector interpolation", "[math]") {
   CHECK_THAT(vec3d1.lerp(vec3d2, 1.0), IsNearlyEqualToVector(vec3d2, 0.000000000001));
 }
 
+TEST_CASE("Vector structured bindings", "[math]") {
+  static_assert(std::tuple_size_v<decltype(vec3b1)> == 3);
+  static_assert(std::tuple_size_v<decltype(vec4f1)> == 4);
+  static_assert(std::tuple_size_v<decltype(Raz::Vector<bool, 1>())> == 1);
+
+  static_assert(std::is_same_v<std::tuple_element_t<0, decltype(vec3i1)>, const int>);
+  static_assert(std::is_same_v<std::tuple_element_t<2, decltype(vec3d1)>, const double>);
+  static_assert(std::is_same_v<std::tuple_element_t<0, decltype(Raz::Vector<bool, 1>())>, bool>);
+  static_assert(std::is_same_v<std::tuple_element_t<0, decltype(Raz::Vector<const bool, 1>())>, const bool>);
+  static_assert(std::is_same_v<std::tuple_element_t<0, std::add_const_t<decltype(Raz::Vector<bool, 1>())>>, const bool>);
+
+  // When using structured bindings, Raz::get<I>(e) is exclusively found using ADL (https://en.cppreference.com/w/cpp/language/adl)
+  static_assert(Raz::get<0>(vec3f1) == vec3f1[0]);
+  static_assert(Raz::get<1>(vec3f1) == vec3f1[1]);
+  static_assert(Raz::get<2>(vec3f1) == vec3f1[2]);
+
+  {
+    const auto [x, y, z] = vec3b2;
+    static_assert(std::is_same_v<decltype(x), const uint8_t>);
+    static_assert(std::is_same_v<decltype(y), const uint8_t>);
+    static_assert(std::is_same_v<decltype(z), const uint8_t>);
+
+    CHECK(x == vec3b2.x());
+    CHECK(y == vec3b2.y());
+    CHECK(z == vec3b2.z());
+
+    // Elements are new variables
+    CHECK_FALSE(&x == &vec3b2.x());
+    CHECK_FALSE(&y == &vec3b2.y());
+    CHECK_FALSE(&z == &vec3b2.z());
+  }
+
+  {
+    const auto& [x, y, z] = vec3d2;
+    // decltype-ing a structured binding doesn't show a reference...
+    static_assert(std::is_same_v<decltype(x), const double>);
+    static_assert(std::is_same_v<decltype(y), const double>);
+    static_assert(std::is_same_v<decltype(z), const double>);
+    // ... but getting the elements independently does...
+    static_assert(std::is_same_v<decltype(Raz::get<0>(vec3d2)), const double&>);
+    static_assert(std::is_same_v<decltype(Raz::get<1>(vec3d2)), const double&>);
+    static_assert(std::is_same_v<decltype(Raz::get<2>(vec3d2)), const double&>);
+
+    CHECK(x == vec3d2.x());
+    CHECK(y == vec3d2.y());
+    CHECK(z == vec3d2.z());
+
+    // ... and the elements are linked as expected
+    CHECK(&x == &vec3d2.x());
+    CHECK(&y == &vec3d2.y());
+    CHECK(&z == &vec3d2.z());
+  }
+
+  {
+    Raz::Vector<bool, 1> boolVec(38);
+
+    {
+      const auto [x] = boolVec;
+      static_assert(std::is_same_v<decltype(x), const bool>);
+      CHECK(x == boolVec.x());
+      CHECK_FALSE(&x == &boolVec.x());
+    }
+
+    {
+      auto [x] = boolVec;
+      static_assert(std::is_same_v<decltype(x), bool>);
+      CHECK(x == boolVec.x());
+      CHECK_FALSE(&x == &boolVec.x());
+    }
+
+    {
+      const auto& [x] = boolVec;
+      static_assert(std::is_same_v<decltype(x), const bool>);
+      static_assert(std::is_same_v<decltype(Raz::get<0>(std::as_const(boolVec))), const bool&>);
+      CHECK(x == boolVec.x());
+      CHECK(&x == &boolVec.x());
+    }
+
+    {
+      auto& [x] = boolVec;
+      static_assert(std::is_same_v<decltype(x), bool>);
+      static_assert(std::is_same_v<decltype(Raz::get<0>(boolVec)), bool&>);
+      CHECK(x == boolVec.x());
+      CHECK(&x == &boolVec.x());
+    }
+
+    {
+      auto&& [x] = std::move(boolVec);
+      static_assert(std::is_same_v<decltype(x), bool>);
+      static_assert(std::is_same_v<decltype(Raz::get<0>(std::move(boolVec))), bool&&>); // xvalue
+      static_assert(std::is_same_v<decltype(Raz::get<0>(Raz::Vector<bool, 1>())), bool&&>); // prvalue
+      CHECK(x == boolVec.x());
+      CHECK(&x == &boolVec.x());
+    }
+  }
+}
+
 TEST_CASE("Vector hash", "[math]") {
   CHECK(vec3b1.hash() == vec3b1.hash());
   CHECK_FALSE(vec3b1.hash() == vec3b2.hash());