命名循环成语：危险吗？ [英] The named loop idiom : dangerous?
问题描述
我读过有关命名循环成语在C ++中的一篇文章：<一href=\"http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Named_Loop\">http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Named_Loop
I've read an article about the "Named Loop Idiom" in C++ : http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Named_Loop
这个成语让我们写这样的事情：
This idiom allows us to write things like that :
named(outer)
for(int i = 0 ; i < rows ; ++i) {
named(inner)
for(int j = 0 ; j < cols ; ++j) {
if(some_condition)
break(outer); // exit the 'outer' loop
}
}
这样的构建已经存在的核心功能在许多语言，如Java的实例。
Such constructs already exists as core feature in many languages, like Java for instance.
根据文章通过定义二恶宏，可以在C ++实现的：
According to the article, it can be implemented in C++ by defining two evil macros :
#define named(blockname) goto blockname; \
blockname##_skip: if (0) \
blockname:
#define break(blockname) goto blockname##_skip;
我知道很多人想驱逐使用转到的。我个人发现在极少数情况很有帮助，特别是当我想要破一堆嵌套循环。这个成语在我看来，作为一个清洁的解决方案，但它是确定在现实code使用它？
I know that many people would like to banish the use of goto. I personally found it helpful in very rare cases, especially when I wanted to break a bunch of nested loops. This idiom appears to me as a cleaner solution for that, but is it ok to use it in real code ?
在文章的讨论页，可以阅读：
On the discussion page of the article, one can read :
别这样，你最终会在地狱
"Do not do this. You'll end up in hell"
所以我的问题是：什么是使用指定的循环成语的弊端？危险吗 ？如果是，为什么？
的奖金的问题：是有可能实现名为继续相似？ （我认为它使用是不可能的的（......指定（...）; ...; ...）{} 语法，但谁知道） 的
Bonus question : is it possible to implement named continue similarly ? (I think it's not possible using the named(...) for(...;...;...) {} syntax, but who knows ?)
编辑：我同意你的看法，重新定义关键字是讨厌。关于使用什么的#define breakLoop（）呢？
EDIT : I agree with you, redefining a keyword is nasty. What about using #define breakLoop() instead?
推荐答案
由于涵盖了意见，#defining 破是有问题的。让我们假设你用别的东西。
As covered in the comments, #defining break is problematic. Let's assume you use something else.
我仍然认为这是危险的。这是一个极不寻常的成语（以C ++程序员），所以他们就不太可能理解，因此他们可能使重大更改。鉴于有不太令人吃惊的 - 因此较少危险 - 的方式来完成同样的事情，我会建议反对
I'd still argue that this is dangerous. It's an extremely unusual idiom (to C++ programmers), so they're less likely to understand, and thus they might make breaking changes. Given that there are less-surprising--and therefore less-dangerous--ways to accomplish the same thing, I would advise against it.
考虑将循环在函数或一个lambda。然后，你可以收益打出来的外循环。作为一个好处，你可以返回有关premature退出，这可能是外code有用的信息。
Consider putting the loops in a function or a lambda. Then you can return to break out of the outer loop. As a benefit, you can return information about the premature exit, which may be useful to the outer code.
这篇关于命名循环成语：危险吗？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
