c++ - 使用 vs typedef 的别名

Question

我在学校实验室工作，在说明中说:

Change the typedef that defines Word_List to a alias declaration (using)

根据我用谷歌搜索的内容，执行此操作的方法是更改​​:

typedef vector<Word_Entry> Word_List;

到:

using Word_List = std::vector<Word_Entry>;

但是当我编译时，出现以下错误:

error: expected nested-name-specifier before 'Word_List'

大部分代码:

#include <iostream>
#include <algorithm>
#include <list>
#include <string>
#include <vector>
#include <fstream>
#include <cctype>
#include <iomanip>

using namespace std;

struct Word_Entry
{
  string ord;
  unsigned cnt;
};

//typedef vector<Word_Entry> Word_List; <-This is what it used to look like
using Word_List = vector<Word_Entry>;


int main()
{
 ...
}

附加信息:

Yes, I am compiling with c++11 
Word_Entry is a struct that stores 2 variables
I have the line "using namespace std;" in the begining of my code
I'm using mingw compiler

Answer 1

你可以在这里看到解决方案:

#include <string>
#include <vector>

using namespace std;

struct Word_Entry
{
  string ord;
  unsigned cnt;
};

//typedef vector<Word_Entry> Word_List; <-This is what it used to look like
using Word_List = vector<Word_Entry>;


int main()
{
}

• http://ideone.com/9mCaq0 (C++) 错误:在“Word_List”之前需要嵌套名称说明符
• http://ideone.com/FdIKcr (C++11) 成功

你有一个配置错误，你没有按照 C++11 规范进行编译。