循环范围内是什么类型? [英] What type is in the range for loop?

问题描述

#include <vector>
#include <iostream>

int main()
{
    std::vector< int > v = { 1, 2, 3 };
    for ( auto it : v )
    {
        std::cout<<it<<std::endl;
    }
}

auto 向什么扩展?是扩展到 int& 还是 int ?

To what is auto expanding? Is it expanding to int& or int?

推荐答案

它扩展为int.如果您需要参考，可以使用

It expands to int. If you want a reference, you can use

for ( auto& it : v )
{
    std::cout<<it<<std::endl;
}

根据C ++ 11标准， auto 被视为简单类型说明符 [7.1.6.2]，因此对它适用相同的规则.其他简单类型说明符.这意味着使用 auto 声明引用与其他没有什么不同.

According to the C++11 standard, auto counts as a simple-type-specifier [7.1.6.2], thus the same rules apply to it as to other simple-type-specifiers. This means that declaring references with auto is no different from anything else.

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