为什么一个额外的逗号不是参数列表，当它被允许在括号初始化允许？ [英] Why is an extra comma not allowed in a parameter list when it is allowed in a brace initialization?

问题描述

这是我的一个老问题，跟进（<一个href=\"http://stackoverflow.com/questions/24156241/is-there-any-relevance-to-an-extra-in-the-end-of-a-brace-initialization\">Is有任何相关性的额外＆QUOT;，＆QUOT;在括号初始化结束）

Following up on an old question of mine (Is there any relevance to an extra "," in the end of a brace initialization?)

有没有为什么参数列表中的函数声明和函数调用尚未作出code世代友好像括号初始化？任何技术原因

Are there any technical reasons why the parameter list in function declarations and function calls has not been made code-generation-friendly like the brace initialization?

我的意思是：

这是确定的，额外的，被忽略了：

This is ok, the extra , is ignored:

int generated_array[] = {
  1,
  2,
  3,
};

有关的一致性，是不是也是有道理允许这样做？

For consistency, wouldn't it also make sense to allow this?

int someFunc(
  int v1,
  int v2,
  int v3,
){...}

int ret_val = someFunc(
  1,
  2,
  3,
);

我看不出它是如何使编译更加复杂，但也许有一些东西我没有想到的。我猜它实际上将简化稍微。

I cannot see how it would make compilation more complicated, but perhaps there is something I'm not thinking of. I would guess it would actually simplify it slightly.

当然，我们可以说，它不是作为支柱初始化是有用的，但应该在哪里code一代人进行至少一点点简单的，如果这是允许的情况下。

Of course one can argue that it's not as useful as the brace initialization, but there should be cases where code generation would be made at least a tiny bit simpler if this was allowed.

推荐答案

在初始化列表尾随逗号的理由是为了便于机器新一代大型静止阵列。这样，如果你碰巧需要编写生成C数组初始化列表中的程序，你可以这样写：

The justification for trailing commas in initializer lists is to allow easy machine-generation of large static arrays. This way, if you happen to need to write a program which generates a C array initializer list, you can just write something like this:

printf("int arr[] = {");
for (int i = 0; i < N; i++) {
    printf("%d, ", i);
}
printf("};");

如果后面的逗号是不允许的，你必须确保它不会产生;和诚实，而这并不难做到，它只是丑陋和颈部疼痛。

If the trailing comma wasn't permitted, you would have to make sure that it's not generated; and honestly, while it's not hard to do, it's just ugly and a pain in the neck.

有没有实际需要机器生成大量功能的参数列表，不过，这些名单固然看起来没有后面的逗号更好的，所以没有必要允许在函数参数和调用同样的事情。

There's no practical need to machine-generate large function parameter lists, though, and these lists admittedly look nicer without a trailing comma, so there's no need to permit the same thing in function parameters and calls.

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