C++ 什么是qualified-id/name 和unqualified-id/name？
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What are qualified-id/name and unqualified-id/name?
提问by M3taSpl0it
I was wondering if someone could explain there terms since I encounter them in many places. I know some basic theory about them but not sure what I know is right or wrong.
我想知道是否有人可以解释这些术语，因为我在很多地方都遇到过它们。我知道一些关于它们的基本理论，但不确定我所知道的是对还是错。
So can any one please explain these terms?
那么任何人都可以解释这些术语吗？
采纳答案by Sadique
A qualified name is one that has some sort of indication of where it belongs, e.g. a class specification, namespace specification, etc. An unqualified name is one that isn't qualified.
限定名称是具有某种指示其所属位置的名称，例如类规范、命名空间规范等。非限定名称是未限定的名称。
Read James McNellis' answer here:
在这里阅读 James McNellis 的回答：
What is a nested name specifier?
Given:
鉴于：
struct A {
struct B {
void F();
};
};
Ais an unqualified-id.::Ais a qualified-idbut has no nested-name-specifier.A::Bis a qualified-idandA::is a nested-name-specifier.::A::Bis a qualified-idandA::is a nested-name-specifier.A::B::Fis a qualified-idand bothB::andA::B::are nested-name-specifiers.::A::B::Fis a qualified-idand bothB::andA::B::are nested-name-specifiers.
A是一个不合格的 id。::A是一个qualified-id，但没有nested-name-specifier。A::B是一个限定 ID并且A::是一个嵌套名称说明符。::A::B是一个限定 ID并且A::是一个嵌套名称说明符。A::B::F是一个qualified-id，B::并且A::B::都是nested-name-specifiers。::A::B::F是一个qualified-id，B::并且A::B::都是nested-name-specifiers。
回答by Alok Save
A qualified name is one that specifies a scope.
Consider the following sample program, the references to coutand endlare qualified names:
限定名称是指定范围的名称。
考虑以下示例程序，对cout和的引用endl是限定名称：
#include <iostream>
int main()
{
std::cout<<"Hello world!"<<std::endl;
return 0;
}
Notice that the use of coutand endlbegan with std::. These make them Qualified names.
请注意，使用cout和endl开始std::。这些使他们成为合格的名称。
If we brought cout and endl into scope by a using declaration or directive*(such as using namespace std;), and used just coutand endljust by themselves , they would have been unqualified names, because they would lack the std::.
如果我们把cout和ENDL到范围通过using声明或指令*（如using namespace std;），只是用来cout和endl自己只是，他们本来不合格的名字，因为他们缺乏std::。
