最近，我想起了为什么我认为给初学者C ++ 是个坏主意。这是一个坏主意，因为在C ++中，真正的混乱是一个美丽但又变态，悲剧和惊人的混乱。尽管社区处于当前状态，但本文并非针对现代 C ++。相反，她部分地继续了Simon Brand的文章 “ C ++中的初始化非常疯狂” ，部分地它是向想要开始深渊学习的每个学生传达的信息。

当学生被告知要学习C时，他们通常会提出异议：

“有人在用吗？”
“这很愚蠢”
“我们为什么要学习C？”
“我们必须学习更好的东西，例如C ++”（笑声）

似乎许多学生认为学习C并不重要（作者：不是），而应该从C ++开始。让我们看一下这是一个荒谬主张的原因之一： 创建一个他妈的变量 。在最初的文章中，Simon Brand建议读者已经熟悉C ++ 11之前版本中的初始化奇异之处。在这里，我们来看其中一些，并进一步介绍。

首先，请允许我在本文中阐明我的个人观点，而不是我在电气和计算机工程系任教的Drexel大学的正式职位。我的演讲通常包含在工程程序课程中，而不是计算机科学课程，也就是说，它们与系统编程和嵌入式系统的关系更大。

一个GIF中的摘要

u / Reddit上的AlexAlabuzhev设法以gif格式重述了整篇文章。（我认为这是Timur Dumler的原创作品）

我对C ++毫无抵触，但在初期阶段，您不需要很多东西。

仅此而已。回家吧与狗散步。洗衣服。打电话给妈妈说你爱她。尝试新食谱。没什么在这里读的家伙。实际上，请考虑一下工程师（即我）传达思想的能力有多差...

一切，我尽力说服！

所以，你还在吗？真正的士兵。如果可以的话，我会给你一枚奖章！还有美味的巧克力牛奶！

现在回到我们通常的编程。

用C初始化

参赛作品

首先，考虑一下C中的初始化，因为出于兼容性方面的考虑，它类似于C ++。它将非常快，因为C非常无聊且简单（ ahem ）。每个初学者都会认真学习这种初始化，因为在C中，它的工作方式不同于许多新的静态类型语言。缺省值为可接受的值初始化，否则将引发编译错误。

int main() {
    int i;
    printf("%d", i);
}

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a.c: In function ‘main’:
a.c:9:5: warning: ‘a.i’ is used uninitialized in this function [-Wuninitialized]
     printf("%d\n", a.i);

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    /* Error! (Well, technically) Initializer lists are 'non-empty' */
    /* struct A a3 = {}; */

    /* ...or use designated initializers if C99 or later */
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    /* default value */
    struct A a5 = default_A;
}

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$ g++ -Wuninitalized -O2 a.cpp
a.cpp: In function ‘int main()’:
a.cpp:9:20: warning: ‘a.A::i’ is used uninitialized in this function [-Wuninitialized]
     std::cout << a.i << std::endl;

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a.cpp: In function ‘int main()’:
a.cpp:9:12: error: C++ designated initializers only available with -std=c++2a or -std=gnu++2a [-Wpedantic]
     A a = {.i = 0};

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}

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$

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}

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$ ./a.out
0 1

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    A a3 = {}; // copy-list-initialization with empty list
    std::cout << a1.i << " " << a2.i << " " << a3.i << std::endl;
}

$ g++ -std=c++11 -pedantic-errors -Wuninitialized -O2 a.cpp
a.cpp: In function ‘int main()’:
a.cpp:9:26: warning: ‘a1.A::i’ is used uninitialized in this function [-Wuninitialized]
     std::cout << a1.i << " " << a2.i << " " << a3.i « std::endl;

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}

$ g++ -std=c++11 -pedantic-errors -Wuninitialized -O2 a.cpp
$

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};
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}

$ g++ -std=c++11 -pedantic-errors -Wuninitialized -O2 a.cpp
a.cpp: In function ‘int main()’:
a.cpp:8:20: warning: ‘a.A::i’ is used uninitialized in this function [-Wuninitialized]
     std::cout << a.i << std::endl;

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}

$ g++ -std=c++11 -pedantic-errors -Wuninitialized -O2 a.cpp
a.cpp: In function ‘int main()’:
a.cpp:7:13: error: could not convert ‘{1}’ from ‘<brace-enclosed initializer list>’ to ‘A’
     A a = {1};

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$

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}

$ g++ -std=c++11 -pedantic-errors -Wuninitialized -O2 a.cpp
a.cpp: In function ‘int main()’:
a.cpp:11:25: warning: ‘b.B::<anonymous>.A::i’ is used uninitialized in this function [-Wuninitialized]
     std::cout << b.i << " " << b.j << std::endl;

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struct A {
    template <typename T>
    A(std::initializer_list<T>) {}
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};

int main() {
    A a1{0};
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    A a3{"hey", "thanks", "for", "reading!"};
    std::cout << a1.i << a2.i << a3.i << std::endl;
}

$ g++ -std=c++17 -pedantic-errors -Wuninitialized -O2 a.cpp
a.cpp: In function ‘int main()’:
a.cpp:12:21: warning: ‘a1.A::i’ is used uninitialized in this function [-Wuninitialized]
     std::cout << a1.i << a2.i << a3.i << std::endl;
                     ^
a.cpp:12:29: warning: ‘a2.A::i’ is used uninitialized in this function [-Wuninitialized]
     std::cout << a1.i << a2.i << a3.i << std::endl;
                             ^
a.cpp:12:37: warning: ‘a3.A::i’ is used uninitialized in this function [-Wuninitialized]
     std::cout << a1.i << a2.i << a3.i << std::endl;

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#include <vector>
#include <string>
int main() {
    std::vector<int> v_1_int{5};
    std::vector<int> v_5_ints(5);
    std::vector<std::string> v_strs = {"neato!", "blammo!", "whammo!", "egh"};
}

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#include <iostream>
struct A {
    A(std::initializer_list<int> l) : i(2) {}
    A(int i = 1) : i(i) {}
    int i;
};
int main() {
    A a1;
    A a2{};
    A a3(3);
    A a4 = {5};
    A a5{4, 3, 2};
    std::cout << a1.i << " "
              << a2.i << " "
              << a3.i << " "
              << a4.i << " "
              << a5.i << std::endl;
}

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$ g++ -std=c++11 -pedantic-errors -Wuninitialized -O2 a.cpp
$ ./a.out
1 1 3 2 2

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, .

用C ++进行初始化真的很疯狂。最好从C开始

一个GIF中的摘要

用C初始化

参赛作品

C++

1.

2.

3.

4.

5. ,

6.

More articles:

用C ++进行初始化真的很疯狂。 最好从C开始

一个GIF中的摘要

用C初始化

参赛作品

C++

1.

2.

3.

4.

5. ,

6.

More articles:

用C ++进行初始化真的很疯狂。最好从C开始