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使用std :: cout和使用:: std :: cout有什么区别？

[英]What's the difference between using std::cout and using ::std::cout?

原文 2016-01-03 17:42:15 5 1 c++/ namespaces

As we already know :: is global namespace. 我们已经知道::是全局名称空间。 And we have already know that using namespace has some downsides. 而我们已经知道的是使用命名空间有一些缺点。

So we decide to type less and type in the beggining of our file using ::std::cout; 因此，我们决定减少键入，然后using ::std::cout;文件的开头using ::std::cout; , but we can also type using std::cout; ，但我们也可以using std::cout; . 。 So is there any difference? 那有什么区别吗？

1 个解决方案

Some people write ::std::cout in order to be absolutely sure that they're getting the cout from the standard library, since the leading :: roots the type at the global namespace. 有些人写::std::cout以绝对确保他们得到的cout标准库中，由于领导::根在全局命名空间的类型。

Otherwise it's conceivable that lookup could find some ::haha::trolling::std::cout name. 否则，可以想到查找可以找到::haha::trolling::std::cout名称。 However, I'd say that this is unlikely. 但是，我想这不太可能。

I do sometimes write ::std in short function templates that are designed to be highly reusable, just for maximum portability, but it's fairly uncommon. 我有时会在简短的函数模板中编写::std ，这些模板被设计为具有高度可重用性，以实现最大的可移植性，但这并不常见。 I've seen one SO contributor who stuck to it religiously, but that's about it. 我见过一位SO贡献者虔诚地坚持下去，但仅此而已。