From 585965ec7ca1a8146a7ac688873f2b8a077a104b Mon Sep 17 00:00:00 2001
From: Alex Hirsch <w4rh4wk@bluephoenix.at>
Date: Thu, 21 Jan 2021 15:08:19 +0100
Subject: [PATCH] Add little features topic

---
 topic/little_features/.gitignore              |  1 +
 topic/little_features/CMakeLists.txt          | 13 ++++
 topic/little_features/conversion_operator.cpp | 19 ++++++
 topic/little_features/execution_policy.cpp    | 15 +++++
 topic/little_features/placement_new.cpp       | 23 ++++++++
 topic/little_features/pointer_to_member.cpp   | 59 +++++++++++++++++++
 6 files changed, 130 insertions(+)
 create mode 100644 topic/little_features/.gitignore
 create mode 100644 topic/little_features/CMakeLists.txt
 create mode 100644 topic/little_features/conversion_operator.cpp
 create mode 100644 topic/little_features/execution_policy.cpp
 create mode 100644 topic/little_features/placement_new.cpp
 create mode 100644 topic/little_features/pointer_to_member.cpp

diff --git a/topic/little_features/.gitignore b/topic/little_features/.gitignore
new file mode 100644
index 0000000..0ec9e7f
--- /dev/null
+++ b/topic/little_features/.gitignore
@@ -0,0 +1 @@
+/build*
diff --git a/topic/little_features/CMakeLists.txt b/topic/little_features/CMakeLists.txt
new file mode 100644
index 0000000..137af03
--- /dev/null
+++ b/topic/little_features/CMakeLists.txt
@@ -0,0 +1,13 @@
+cmake_minimum_required(VERSION 3.16)
+project(little_features CXX)
+
+file(GLOB srcs *.cpp)
+foreach(src IN LISTS srcs)
+  get_filename_component(exe ${src} NAME_WE)
+  add_executable(${exe} ${src})
+  target_compile_features(${exe} PRIVATE cxx_std_17)
+  set_target_properties(${exe} PROPERTIES CXX_EXTENSIONS OFF)
+  target_compile_options(${exe} PRIVATE
+    $<$<CXX_COMPILER_ID:GNU,Clang,AppleClang>:-Wall -Wextra -pedantic>)
+  target_link_libraries(${exe} -ltbb)
+endforeach()
diff --git a/topic/little_features/conversion_operator.cpp b/topic/little_features/conversion_operator.cpp
new file mode 100644
index 0000000..920d1d9
--- /dev/null
+++ b/topic/little_features/conversion_operator.cpp
@@ -0,0 +1,19 @@
+#include <cassert>
+
+struct Vec3 {
+	float x, y, z;
+};
+
+struct Vec2 {
+	float x, y;
+	operator Vec3() const { return Vec3{x, y, 0}; }
+};
+
+int main()
+{
+	Vec2 v2{1, 2};
+
+	Vec3 v3 = v2;
+
+	assert(v3.x == 1 && v3.y == 2 && v3.z == 0);
+}
diff --git a/topic/little_features/execution_policy.cpp b/topic/little_features/execution_policy.cpp
new file mode 100644
index 0000000..7ea3652
--- /dev/null
+++ b/topic/little_features/execution_policy.cpp
@@ -0,0 +1,15 @@
+#include <algorithm>
+#include <array>
+#include <execution>
+#include <iostream>
+
+int main()
+{
+	std::vector<int> numbers;
+	for (auto i = 0; i < 1000; i++) {
+		numbers.push_back(i);
+	}
+
+	// Output should be malformed since there is no synchronization in place.
+	std::for_each(std::execution::par, numbers.begin(), numbers.end(), [](int i) { std::cout << i << "\n"; });
+}
diff --git a/topic/little_features/placement_new.cpp b/topic/little_features/placement_new.cpp
new file mode 100644
index 0000000..92cb562
--- /dev/null
+++ b/topic/little_features/placement_new.cpp
@@ -0,0 +1,23 @@
+#include <cstdlib>
+#include <iostream>
+
+struct Point {
+	Point(float x, float y) : x(x), y(y) { std::cout << "Constructed at address: " << this << "\n"; }
+	~Point() { std::cout << "Deconstructed at address: " << this << "\n"; }
+	float x, y;
+};
+
+int main()
+{
+	auto memory = malloc(sizeof(Point));
+
+	// Construct a point at a specific location.
+	Point *p = new (memory) Point(1.0f, 2.0f);
+
+	std::cout << "x: " << p->x << "\n";
+
+	// Need to manually invoke the destructor.
+	p->~Point();
+
+	free(memory);
+}
diff --git a/topic/little_features/pointer_to_member.cpp b/topic/little_features/pointer_to_member.cpp
new file mode 100644
index 0000000..e0375ea
--- /dev/null
+++ b/topic/little_features/pointer_to_member.cpp
@@ -0,0 +1,59 @@
+#include <cassert>
+
+struct Point {
+	float x, y;
+};
+
+struct Rect {
+	Point tl, br;
+	float area() const { return (br.x - tl.x) * (br.y - tl.y); }
+};
+
+class IShape {
+  public:
+	virtual float area() const { assert(false); };
+	virtual ~IShape() {}
+};
+
+class Square : public IShape {
+  public:
+	Square(float extend) : m_extend(extend) {}
+	float area() const override { return m_extend * m_extend; }
+
+  private:
+	float m_extend;
+};
+
+int main()
+{
+	Rect r1{{1, 1}, {4, 4}};
+	assert(r1.area() == 9.0f);
+
+	Rect *r1_ptr = &r1;
+	assert(r1_ptr->area() == 9.0f);
+
+	// member variable pointer
+	auto tl_mem_ptr = &Rect::tl; // Point Rect::*tl_mem_ptr
+
+	assert((r1.*tl_mem_ptr).x == 1.0f);
+
+	assert((r1_ptr->*tl_mem_ptr).x == 1.0f);
+
+	// member function pointer
+	auto area_memfn_ptr = &Rect::area; // float (Rect::*area_memfn_ptr)() const
+
+	assert((r1.*area_memfn_ptr)() == 9.0f);
+
+	assert((r1_ptr->*area_memfn_ptr)() == 9.0f);
+
+	// Virtual
+	Square square{2.0f};
+	IShape *shape_ptr = &square;
+
+	// virtual member function pointer
+	auto virt_area_memfn_ptr = &IShape::area; // float (IShape::*virt_area_memfn_ptr)() const
+
+	assert((square.*virt_area_memfn_ptr)() == 4.0f);
+
+	assert((shape_ptr->*virt_area_memfn_ptr)() == 4.0f);
+}