Question

Is a namespace the same thing as scope in C++ programming language? Are these two words synonyms and can be used interchangably?

Answer 1

页: 1 名称空间是一种范围,但范围有若干种,是国名空间。一些实例:

block scope: symbols (usually local variables) declared within a statement block enclosed in {...};
function scope: a function s outermost block scope;
class scope: the members of a class.

Answer 2

并非完全。

In C++, a scope is generally determined by pair of opening and closing braces: { and }, this includes:

namespaces
classes and structs
functions and methods
simple "blocks" within functions or methods

然而,一些声明有少数例外或特殊性,这些声明可能会带来一些变量,这些变量将在其眼前的范围之内:

for (int i = 0; i < 10; ++i) {
  // i accessible here
}

while (int c = getchar()) {
  // c accessible here
}

try {
  // ...
} catch(std::exception const& e) {
  // e accessible here
}

void foo(int i) {
  // i accessible here
}

并且有最令人惊讶的<代码>。

if (int var = /**/)
{
  // var is accessible here
}
else
{
  // var is accessible here too!
}

这些范围是:

由于C规则(C++也遵循)使<代码>{<>/代码>和<代码>>>>>>>>>>>>>在表述中选取:

for (int i = 0; i < 10; ++i) std::cout << i << "
";
// i no longer accessible here

模板参数也有其范围:这些参数在申报点活到生命,直到其课目或职能结束。

template <typename U>
void foo() {
} // U accessible up until this point

最后,还有“最外部”的范围,即全球名称空间,即“可支配”范围。

Answer 3

没有。

A scope is pretty much similar to an object s lifetime - similar, not the same.

class A;

//....
{
   A a;  //begin scope for object a
}
//object a is out of scope

A namespace is a useful way to group declarations and definitions in C++.

你们可以指定一个名称空间,但范围远大于此。见范围解决操作者:一种方法或变量可以是类别范围的一部分,而不是在名称空间。

Answer 4

Wikipedia s articles on Scope &Variables 应当有所帮助。

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