最卢的瑟's homework

.gitignore

@@ -28,3 +28,4 @@ node_modules
 /public
 /resources
 go.sum
+cmake-build

src/群友提交/第01题/brian.cpp

@@ -0,0 +1,24 @@
+//
+// loser_homework / brian.cpp
+// Created by brian on 2024 Apr 03.
+//
+
+#include <vector>
+#include <functional>
+#include <iostream>
+#include <algorithm>
+
+template<typename T, typename Func>
+requires std::invocable<Func, T&>
+std::vector<T>& operator|(std::vector<T>& vec, Func const& func) {
+  std::ranges::for_each(vec, func);
+  return vec;
+}
+
+
+int main() {
+  std::vector v{1, 2, 3};
+  std::function f{[](const int& i) { std::cout << i << ' '; }};
+  auto f2 = [](int& i) { i *= i; };
+  v | f2 | f;
+}

src/群友提交/第04题/brian.cpp

@@ -0,0 +1,34 @@
+//
+// loser_homework / brian.cpp
+// Created by brian on 2024 Apr 03.
+//
+#include<iostream>
+
+class ComponentBase {
+protected:
+  static inline std::size_t component_type_count = 0;
+};
+
+template<typename T>
+class Component : public ComponentBase {
+public:
+  static size_t component_type_id() {
+    static size_t unique_id = component_type_count++;
+    return unique_id;
+  }
+};
+
+class A : public Component<A> {};
+
+class B : public Component<B> {};
+
+class C : public Component<C> {};
+
+int main() {
+  std::cout << A::component_type_id() << std::endl;
+  std::cout << B::component_type_id() << std::endl;
+  std::cout << B::component_type_id() << std::endl;
+  std::cout << A::component_type_id() << std::endl;
+  std::cout << A::component_type_id() << std::endl;
+  std::cout << C::component_type_id() << std::endl;
+}

src/群友提交/第05题/brian.cpp

@@ -0,0 +1,86 @@
+//
+// loser_homework / scope_guard.cpp
+// Created by brian on 2024 Apr 03.
+//
+#include <cstdio>
+#include <cassert>
+
+#include <stdexcept>
+#include <functional>
+
+struct X {
+  X() { puts("X()"); }
+
+  X(const X&) { puts("X(const X&)"); }
+
+  X(X&&) noexcept { puts("X(X&&)"); }
+
+  ~X() { puts("~X()"); }
+};
+
+struct scope_guard {
+  template<typename F, typename... A>
+  requires std::invocable<F, A...>
+  scope_guard(F&& func, A&& ...args) {
+    gc = [&func, &args...]() mutable {
+      /**
+      * @brief https://en.cppreference.com/w/cpp/utility/functional/invoke
+      * invoke： 如果\p func 是成员函数， 则\p ...args 的第一个参数是对应的对象(\p &,* )
+      */
+      std::invoke(std::forward<F>(func), args...);
+    };
+  }
+  ~scope_guard() { gc(); }
+  scope_guard(const scope_guard&) = delete;
+  scope_guard& operator=(const scope_guard&) = delete;
+
+private:
+  std::function<void()> gc;
+};
+
+
+int main() {
+  {
+    // scope_guard的作用之一，是让各种C风格指针接口作为局部变量时也能得到RAII支持
+    // 这也是本题的基础要求
+    FILE* fp = nullptr;
+    try {
+      fp = fopen("test.txt", "a");
+      auto guard = scope_guard([&] {
+        fclose(fp);
+        fp = nullptr;
+      });
+
+      throw std::runtime_error{"Test"};
+    } catch (std::exception& e) {
+      puts(e.what());
+    }
+    assert(fp == nullptr);
+  }
+  puts("----------");
+  {
+    // 附加要求1，支持函数对象调用
+    struct Test {
+      void operator()(X* x) {
+        delete x;
+      }
+    } t;
+    auto x = new X{};
+    auto guard = scope_guard(t, x);
+  }
+  puts("----------");
+  {
+    // 附加要求2，支持成员函数和std::ref
+    auto x = new X{};
+    {
+      struct Test {
+        void f(X*& px) {
+          delete px;
+          px = nullptr;
+        }
+      } t;
+      auto guard = scope_guard{&Test::f, &t, std::ref(x)};
+    }
+    assert(x == nullptr);
+  }
+}

src/群友提交/第06题/brian.md

@@ -0,0 +1,5 @@
+为保证atomic对象的原子性，复制和移动都是不允许的。
+
+C++17之前 `std::atomic<int> n = 6;`不合法是因为atomic只支持列表初始化， 写成 `std::atomic<int> n = {6};`就可以通过编译了； 
+
+17+之后的`std::atomic<int> n = 6;`其实是原地构造，合法。