从嵌套块的预期块中访问变量 [英] accessing variables from an intended block of nested blocks

问题描述

在下面的程序中，如何从块C中的块A中检索aa的值？
我们只能使用范围解析运算符访问最外层的全局aa。

In the program below, how to retrieve value of aa from Block A in Block C? We can only access the outermost global aa using scope resolution operator.

已知的溶剂：
1.在不同的块$ b $中使用不同的指针b 2.在使用当前块的变量之前，先在父块中使用变量

Known solutoins: 1. Use different pointers in different blocks 2. Use the variable in parent block before using the current block's variable

我正在寻找其他替代解决方案

I am looking for any other alternative solution

我知道这不是好代码。

I know that this is not good code. Just curious in understanding how to achieve it.

#include <iostream>
#include <cstdio>

using namespace std;

// Global
int aa = 10;

int main()
{
    // Main
    int aa = 20;

    {
        // Block A
        int aa = 30;

        {
            // Block B
            int aa = 40;

            {
                // Block C
                int aa = 50;

                cout << "block C " << aa << endl;
                cout << "block A " << ????? << endl;
                cout << "global" << ::aa << endl;
            }

            cout << "block B " << aa << endl;
        }

        cout << "block A " << aa << endl;
    }

    cout << "main " << aa << endl;

    return 0;
}

推荐答案

我知道这不是好代码。只是好奇地了解如何实现。

I know that this is not good code. Just curious in understanding how to achieve it.

您不能。

未经修饰使用变量 aa 将使用最接近范围的变量。

修饰使用变量 :: aa ，将使用函数外部作用域中的值。

装饰使用变量< NS> ::: aa ，将使用名称空间< NS> 范围内的那个。

Undecorated use of the variable aa will use the one that is in the nearest scope.
Decorated use of the variable, ::aa, will use the one that is in the scope outside the function.
Decorated use of the variable, <NS>::aa, will use the one that is in the scope of the namespace <NS>.

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