[英]'for_each_n' is not a member of 'std' in C++17
I have small piece of code for std::for_each_n
loop.我有一小段用于
std::for_each_n
循环的代码。 I tried running it on inbuilt Coliru compiler GCC C++17 using following command :我尝试使用以下命令在内置Coliru编译器 GCC C++17 上运行它:
g++ -std=c++1z -O2 -Wall -pedantic -pthread main.cpp && ./a.out
But compiler give an error that " 'for_each_n' is not a member of 'std' ".但是编译器给出了一个错误, “'for_each_n' 不是 'std' 的成员”。
My code is bellow which is copied from cppreference .我的代码如下,是从cppreference复制的。
#include <algorithm>
#include <iostream>
#include <vector>
int main()
{
std::vector<int> ns{1, 2, 3, 4, 5};
for (auto n: ns) std::cout << n << ", ";
std::cout << '\n';
std::for_each_n(ns.begin(), 3, [](auto& n){ n *= 2; });
for (auto n: ns) std::cout << n << ", ";
std::cout << '\n';
}
So, Why I'm getting an error?那么,为什么我会收到错误消息?
There is nothing wrong with your code.您的代码没有任何问题。 The issue is that libstdc++ does not support
std::for_each_n
as of yet.问题是 libstdc++ 目前还不支持
std::for_each_n
。 If we look at header that defines std::for_each
we see it does not exist.如果我们查看定义
std::for_each
头文件,我们会发现它不存在。
However, if you have access to libc++, their header from the official mirror does implement std::for_each_n
但是,如果您可以访问 libc++,那么官方镜像中的标头确实实现了
std::for_each_n
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