C++11 auto实践

测试一

	#include <iostream>
	#include <typeinfo>

	using namespace std;

	int main()
	{
		auto x = 5;
		std::cout << typeid(x).name() << std::endl;

		auto pi = new auto(1);
		std::cout << typeid(pi).name() << std::endl;

		const auto *v = &x, u = 6;
		std::cout << typeid(v).name() << std::endl;
		std::cout << typeid(u).name() << std::endl;

		static auto y = 0.0;
		std::cout << typeid(y).name() << std::endl;

		// auto int r; // error

		// auto s; // error

	    return 0;
	}

	output：
	int
	int *
	int const *
	int
	double

测试二

  #include <iostream>
  #include <typeinfo>

  int main()
  {
      int x = 0;
      const auto *v = &x, u = 6.0;
      std::cout << typeid(v).name() << std::endl;
      std::cout << typeid(u).name() << std::endl;
      return 0;
  }
  output:
  autoTest.cpp: In function ‘int main()’:
  autoTest.cpp:7:29: error: inconsistent deduction for ‘const auto’: ‘int’ and then ‘double’
       const auto *v = &x, u = 6.0;

测试三

  #include <iostream>
  #include <typeinfo>

  int main()
  {
      int x = 0;
      auto *a = &x;
      std::cout << typeid(a).name() << std::endl;

      auto b = &x;
      std::cout << typeid(b).name() << std::endl;

      auto &c = x;
      std::cout << typeid(c).name() << std::endl;

      auto d = c;
      std::cout << typeid(d).name() << std::endl;

      const auto e = x;
      std::cout << typeid(e).name() << std::endl;

      auto f = e;
      std::cout << typeid(f).name() << std::endl;

      const auto &g = x;
      std::cout << typeid(g).name() << std::endl;

      auto &h = g;
      std::cout << typeid(h).name() << std::endl;
  }
  output:
  int *
  int *
  int
  int
  int
  int
  int
  int

测试四（auto限制）

  #include <iostream>
  #include <typeinfo>

  void func(auto a = 1) {} // error:auto 不能用于函数参数

  struct Foo
  {
      auto var1_ = 0; // error:auto 不能用于非静态成员函数
      static const auto var2_ = 0;
  };

  template <typename T>
  sturct Bar{};

  int main()
  {
      int arr[10] = { 0 };
      auto aa = arr;

      auto rr[10] = arr; // error
      Bar<int> bar;
      Bar<auto> bb = bar; // error

      return 0
  }

C++11 auto实践

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