什么是逗号的阵列和结构初始化的意义何在？ [英] What is the significance of comma in array and structure initialization?

问题描述

虽然通过一些codeS浏览，我遇到这种初始化方法：

While browsing through some codes, i came across this method of initialization:

#include<stdio.h>

struct trial{
    int x, y;
};

int main(){
    int a[10] = {0,1, };//comma here
    struct trial z = {1, };//comma here
    return 0;
}

这是什么逗号运算的意义是什么？如果逗号运算符被删除我不觉得在初始化的方法有什么区别。

What is the significance of this comma operator? I do not find any difference in the method of initialization if the comma operator is removed.

推荐答案

这是有道理的，如果你生成脚本，code。它使你的脚本简单。没有边缘的情况。特别是，你不打扰你是否需要添加一个，第一，写多了一个项目之前;你只写一个项目接着一个逗号，你就大功告成了！

It makes sense if you generate such code from scripts. It keeps your script simple. No edge-cases. In particular, you don't bother whether you need to add a , first, before writing one more item; you just write one item followed by a comma and you're done!

您不关心的第一项或最后一项。所有项目的相同的，如果有一个结尾逗号。

You don't care about the first item or last item. All items are same if there is a trailing comma.

但从code代点思考。这将开始制作感。

Think from code-generation point of view. It would start making sense.

请参阅产生此种code这个python脚本：

See this python script that generates such code:

print ("int a[] = {")
for item in items:
    print (item + ",")
print ("};")

这很简单。现在试着写一个code没有尾随逗号。它不会是的是的简单。

该标准还允许尾随逗号枚举定义：

The standard also allows trailing-comma in enum definition:

enum A
{
    X,
    Y,
    Z, //last item : comman is okay
};

希望有所帮助。

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